The ontogeny of the immune system and the effect thereon by type of infant feeding is incompletely understood. We analyzed frequencies and composition of immune cells in blood of breastfed (BF) and formula-fed (FF) infants at 1.5, 4, and 6 mo of age. Three formulas with the same protein concentration but with varying levels of alpha-lactalbumin and caseinoglycomacropeptide were compared. Twenty-nine exclusively BF infants served as reference, and 17 infants in each formula group completed the study. Whole blood and PBMCs were analyzed by flow cytometry and immunoflow cytometry, respectively. Leukocyte count of BF infants increased with time due to increased frequency of neutrophils. Lymphocyte count was high at 1.5 mo and was unchanged over time, as were the relative proportions of CD4+ alphabetaT cells, CD8+ alphabetaT cells, B cells, NK cells, and gammadeltaT cells. Most CD45R0+CD3+ cells were HLA-DR- and hence memory cells. Compared with breastfeeding, formula feeding resulted in a significant decrease in proportion of NK cells, but a significant increase in naive CD4+ alphabetaT cells and an elevated CD4-to-CD8 ratio, that is, 3.3 in the combined FF groups compared with 2.6 in the BF group. No significant differences were found between the three groups of FF infants. In conclusion, blood cells of lymphoid lineage did not change significantly in frequencies or composition from 1.5 to 6 mo of age in BF infants. In contrast, FF infants displayed an ongoing maturation of adaptive immunity cells and a delayed recruitment of innate immunity cells as compared with BF infants.
The Yersinia pseudotuberculosis invasin protein was found to be a potent inducer of pseudopodia formation and chemotactic and haptotactic migration in human T lymphocytes. Checkerboard analysis confirmed that migration was directional. The Yersinia invasin triggered migration of otherwise poorly migratory normal T cells on fibronectin and in particular on collagen type IV, and augmented the migration of leukemic T cell lines on these components. Invasin-induced lymphocyte migration was inhibited by staurosporin that selectively prevented pseudopodia formation but, noteworthy, augmented adhesion. The motogenic and attractant properties of invasin (Inv) were mediated via beta1-integrins, as shown by lack of effect of Inv on the motility of a beta1-integrin-negative lymphoid cell line and inhibition of invasin-induced lymphocyte motility by anti-beta1 Abs. Inv was markedly more effective than the extracellular matrix components fibronectin, collagen type IV, and laminin, which also interact with lymphocyte beta1-integrins, with respect to induction of pseudopodia, chemotaxis, and haptotaxis. Thus, Yersinia invasin is a model ligand for induction of lymphocyte motility via beta1-integrins. The extraordinary capacity of Inv to trigger and guide T lymphocyte motility and potentiate lymphocyte migration to extracellular matrix components may be of pathogenetic significance for the movement of lymphocytes to extraintestinal sites secondary to Yersinia infection.
Every breath we take contains potentially harmful pathogens or allergens. Dendritic cells (DCs), monocytes, and macrophages are essential in maintaining a delicate balance of initiating immunity without causing collateral damage to the lungs because of an exaggerated inflammatory response. To document the diversity of lung mononuclear phagocytes at steady-state, we performed bronchoscopies on 20 healthy subjects, sampling the proximal and distal airways (bronchial wash and bronchoalveolar lavage, respectively), as well as mucosal tissue (endobronchial biopsies). In addition to a substantial population of alveolar macrophages, we identified subpopulations of monocytes, myeloid DCs (MDCs), and plasmacytoid DCs in the lung mucosa. Intermediate monocytes and MDCs were highly frequent in the airways compared with peripheral blood. Strikingly, the density of mononuclear phagocytes increased upon descending the airways. Monocytes from blood and airways produced 10-fold more proinflammatory cytokines than MDCs upon ex vivo stimulation. However, airway monocytes were less inflammatory than blood monocytes, suggesting a more tolerant nature. The findings of this study establish how to identify human lung mononuclear phagocytes and how they function in normal conditions, so that dysregulations in patients with respiratory diseases can be detected to elucidate their contribution to immunity or pathogenesis.
Two new 5'-untranslated region (5'UTR) exons were identified in the human gene for the lymphocyte-specific endonuclease recombination activating gene-1 (RAG1) required for the somatic recombination yielding functional Ag receptors. These 5'UTR exons were used in three different splice forms by jejunal lymphocytes of the T cell lineage. RAG1 mRNA containing the previously described 5'UTR exon was not expressed in these cells. Conversely, one of the new 5'UTR exons was not expressed in thymus. The new RAG1 mRNA splice forms were all expressed in immature T cells (CD2(+)CD7(+)CD3(-)). This cell population also expressed high levels of mRNA for the pre-T alpha-chain. In situ hybridization demonstrated jejunal cells expressing the new splice forms of RAG1 mRNA, both intraepithelially and in lamina propria. Pre-T alpha-chain mRNA-expressing cells were detected at the same sites. These results strongly suggest ongoing TCR gene rearrangement in human small intestinal mucosa, yielding T cells specially adapted for this environment. This seems to be achieved by two parallel processes, extrathymic T cell development and peripheral Ag-driven TCR editing.
Little is known about target organ-infiltrating NK cells in type 1 diabetes and other autoimmune diseases. In this study, we identified NK cells with a unique phenotype in the pancreas of NOD mice. Pancreatic NK cells, localized to the endocrine and exocrine parts, were present before T cells during disease development and did not require T cells for their infiltration. Furthermore, NK cells, or NK cell precursors, from the spleen could traffic to the pancreas, where they displayed the pancreatic phenotype. Pancreatic NK cells from other mouse strains shared phenotypic characteristics with pancreatic NK cells from NOD mice, but displayed less surface killer cell lectin-like receptor G1, a marker for mature NK cells that have undergone proliferation, and also did not proliferate to the same extent. A subset of NOD mouse pancreatic NK cells produced IFN-gamma spontaneously, suggesting ongoing effector responses. However, most NOD mouse pancreatic NK cells were hyporesponsive compared with spleen NK cells, as reflected by diminished cytokine secretion and a lower capacity to degranulate. Interestingly, such hyporesponsiveness was not seen in pancreatic NK cells from the nonautoimmune strain C57BL/6, suggesting that this feature is not a general property of pancreatic NK cells. Based on our data, we propose that NK cells are sentinel cells in a normal pancreas. We further speculate that during inflammation, pancreatic NK cells initially mediate proinflammatory effector functions, potentially contributing to organ-specific autoimmunity, but later become hyporesponsive because of exhaustion or regulation.
A role for regulatory lymphocytes has been demonstrated in the pathogenesis of type 1 diabetes in the NOD mouse but the nature of these cells is debated. CD1d-restricted NKT lymphocytes have been implicated in this process. Previous reports of reduced diabetes incidence in NOD mice in which the numbers of NKT cells are artificially increased have been attributed to the enhanced production of IL-4 by these cells and a role for classical NKT cells, using the Valpha14-Jalpha18 rearrangement. We now show that overexpression in NOD mice of CD1d-restricted TCR Valpha3.2(+)Vbeta9(+) NKT cells producing high levels of IFN-gamma but low amounts of IL-4 leads to prevention of type 1 diabetes, demonstrating a role for nonclassical CD1d-restricted NKT cells in the regulation of autoimmune diabetes.
T cell anergy is characterized by the inability of the T cell to produce IL-2 and proliferate. It is reversible by the addition of exogenous IL-2. A similar state of unresponsiveness is observed when the proliferative response of murine CD4+CD25- T cells is suppressed in vitro by coactivated CD4+CD25+ T cells. We have developed a suppression system that uses beads coated with anti-CD3 and anti-CD28 Abs as surrogate APCs to study the interaction of CD4+CD25+ and CD4+CD25- T cells in vitro. CD4+CD25+ T cell-induced suppression, in this model, was not abrogated by blocking the B7-CTLA-4 pathway. When the CD4+CD25- T cells were separated from the CD4+CD25+ suppressor cells after 24 h of coactivation by the Ab-coated beads, the CD4+CD25- T cells were unable to proliferate or to produce IL-2 upon restimulation. The induction of this anergic phenotype in the CD4+CD25- T cells correlated with the up-regulated expression of the gene related to anergy in lymphocytes (GRAIL), a novel anergy-related gene that acts as a negative regulator of IL-2 transcription. This system constitutes a novel mechanism of anergy induction in the presence of costimulation.
Haemophilus influenzae is a Gram-negative human pathogen that resides in the upper respiratory tract. Encapsulated H. influenzae type b (Hib) and type f (Hif) are the most common serotypes associated with invasive disease. H. influenzae displays various strategies to circumvent the host innate immune response, including the bactericidal effect of the complement system. In this study, we identified an H. influenzae lipoprotein having the ability to bind factor H (FH), the major regulator of the alternative pathway of complement activation. This protein, named protein H (PH), was surface exposed and was found in all clinical Hib and Hif isolates tested. Deletion of the gene encoding for PH (lph) in Hib and Hif significantly reduced the interaction between bacteria and FH. When Hib and Hif PH variants were separately expressed in nontypeable ( unencapsulated) H. influenzae, which did not bind FH, an increased FH affinity was observed. We recombinantly expressed the two PH variants in Escherichia coli, and despite sharing only 56% identical amino acids, both FH-binding Haemophilus proteins similarly interacted with the complement regulator FH short consensus repeats 7 and 18-20. Importantly, Hib and Hif resistance against the bactericidal effect of human serum was significantly reduced when bacterial mutants devoid of PH were tested. In conclusion, we have characterized a hitherto unknown bacterial protein that is crucial for mediating an interaction between the human pathogen H. influenzae and FH. This novel interaction is important for H. influenzae resistance against complement activation and will consequently promote bacterial pathogenesis.
Chronic granulomatous disease, an inherited disorder of the NADPH oxidase in which phagocytes are defective in the generation of superoxide anion and downstream reactive oxidant species, is characterized by severe bacterial and fungal infections and excessive inflammation. Although NADPH oxidase isoforms exist in several lineages, reactive oxidant generation is greatest in neutrophils, where NADPH oxidase has been deemed vital for pathogen killing. In contrast, the function and importance of NADPH oxidase in macrophages are less clear. Therefore, we evaluated susceptibility to pulmonary aspergillosis in globally NADPH oxidase-deficient mice versus transgenic mice with monocyte/macrophage-targeted NADPH oxidase activity. We found that the lethal inoculum was >100-fold greater in transgenic versus globally NADPH oxidase-deficient mice. Consistent with these in vivo results, NADPH oxidase in mouse alveolar macrophages limited germination of phagocytosed Aspergillus fumigatus spores. Finally, globally NADPH oxidase-deficient mice developed exuberant neutrophilic lung inflammation and proinflammatory cytokine responses to zymosan, a fungal cell wall-derived product composed principally of particulate beta-glucans, whereas inflammation in transgenic and wild-type mice was mild and transient. Taken together, our studies identify a central role for monocyte/macrophage NADPH oxidase in controlling fungal infection and in limiting acute lung inflammation. The Journal of Immunology, 2013, 190: 4175-4184.
The early effects of interferon (IFN) on the synthesis of protein in human nylon wool-nonadherent lymphocytes have been stimulated by use of two-dimensional electrophoresis. IFN-alpha or -beta as well as Escherichia coli-produced IFN-alpha 2 induced the rapid formation of seven proteins (Mr 80, 75, 62, 53, 38, 36, and 33 kD). At least five proteins were expressed within 2 hr of incubation with IFN. The synthesis of the seven proteins seemed to require rapid transcription of new RNA, because actinomycin D markedly inhibited their formation only when added less than 30 min after IFN. A good correlation was found between the ability of actinomycin D to inhibit both the formation of new proteins and the augmentation of natural killer (NK) cell activity. Screening of a panel of 10 hematopoietic and two anchorage-dependent cell lines revealed that p62 and p38 were induced in most cell lines, whereas p80 and p33 were preferentially induced in lymphoid cell lines. Three proteins could not be induced by IFN in any of the 12 cell lines, and thus could represent molecules mediating differentiated functions, possibly involved in NK cell function.
Mast cell tryptase is a tetrameric serine protease that is stored in complex with negatively charged heparin proteoglycans in the secretory granule. Tryptase has potent proinflammatory properties and has been implicated in diverse pathological conditions such as asthma and fibrosis. Previous studies have shown that tryptase binds tightly to heparin, and that heparin is required in the assembly of the tryptase tetramer as well as for stabilization of the active tetramer. Because the interaction of tryptase with heparin is optimal at acidic pH, we investigated in this study whether His residues are of importance for the heparin binding, tetramerization, and activation of the tryptase mouse mast cell protease 6. Molecular modeling of mouse mast cell protease 6 identified four His residues, H35, H106, H108, and H238, that are conserved among pH-dependent tryptases and are exposed on the molecular surface, and these four His residues were mutated to Ala. In addition, combinations of different mutations were prepared. Generally, the single His-Ala mutations did not cause any major defects in heparin binding, activation, or tetramerization, although some effect of the H106A mutation was observed. However, when several mutations were combined, large defects in all of these parameters were observed. Of the mutants, the triple mutant H106A/H108A/H238A was the most affected with an almost complete inability to bind to heparin and to form active tryptase tetramers. Taken together, this study shows that surface-exposed histidines mediate the interaction of mast cell tryptase with heparin and are of critical importance in the formation of active tryptase tetramers.
A key feature of the immune system is the paradigm that one lymphocyte has only one Ag specificity that can be selected for or against. This requires that only one of the alleles of genes for AgR chains is made functional. However, the molecular mechanism of this allelic exclusion has been an enigma. In this study, we show that B lymphocytes with E2A that cannot be inhibited by calmodulin are dramatically defective in allelic exclusion of the IgH locus. Furthermore, we provide data supporting that E2A, PAX5, and the RAGs are in a VDJ recombination complex bound to key sequences on the Igh gene. We show that pre-BCR activation releases the VDJ recombination complex through calmodulin binding to E2A. We also show that pre-BCR signaling downregulates several components of the recombination machinery, including RAG1, RAG2, and PAX5, through calmodulin inhibition of E2A.
Differentiation of B lymphocytes into Ab-secreting plasmablasts and plasma cells is Ag driven. The interaction of Ag with the membrane-bound Ab of the BCR is critical in determining which clones enter the plasma cell response. However, not much is known about the coupling between BCR activation and the shift in transcription factor network from that of a B cell to that of ASC differentiation. Our genome-wide analysis shows that Ab-secreting cell differentiation of mouse B cells is induced by BCR activation through very fast regulatory events from the BCR. We identify activation of IFN regulatory factor-4 and down-regulation of Pax5, Bcl-6, MITF, Ets-1, Fli-1, and Spi-B gene expression as immediate early events. Furthermore, the transcription factor E2A is required for the rapid key down-regulations after BCR activation, and the Ca(2+) sensor protein calmodulin has the corresponding regulatory effect as BCR activation. Moreover, mutants in the calmodulin binding site of E2A show that Ca(2+) signaling through calmodulin inhibition of E2A is essential for the rapid down-regulation of immediate early genes after BCR activation in initiation of plasma cell differentiation.
During mammalian pregnancy maternal-fetal tolerance involves a number of immunosuppressive factors produced by placenta. Recently, placenta-derived exosomes have emerged as new immune regulators in the maternal immune tolerance. Exosomes are membrane nanovesicles with defined morphology, which are secreted from endosomal multivesicular bodies (MVB) upon fusion with the plasma membrane. Previously, we reported that the MHC class I chain-related (MIC) proteins A and B, human ligands of the activating NK cell receptor NKG2D, are expressed by placenta, sorted to MVB of syncytiotrophoblast and probably released via MIC-bearing exosomes. In this report, we show that the second family of human NKG2D ligands, the UL-16 binding proteins (ULBP), is also expressed by placenta. Importantly, this expression was not due to placental CMV infection. Immunoelectron microscopy disclosed that ULBP1-5 are produced and retained in MVB of the syncytiotrophoblast on microvesicles/exosomes. Using human placenta explant cultures and different assays, we demonstrate that exosomes bearing NKG2D ligands are released by human placenta. Isolated placental exosomes carried ULBP1-5 and MIC on their surface and induced down-regulation of the NKG2D receptor on NK, CD8(+), and gammadelta T cells, leading to reduction of their in vitro cytotoxicity without affecting the perforin-mediated lytic pathway. Release of placental NKG2D ligands via exosomes is an alternative mechanism for generation of bioactive soluble form of these ligands. These findings highlight a role for NKG2D ligand-bearing placental exosomes in the fetal immune escape and support the view of placenta as a unique immunosuppressive organ.
Type 1 diabetes (T1D) is a chronic autoimmune disease that results from T cell-mediated destruction of pancreatic β cells. CD1d-restricted NKT lymphocytes have the ability to regulate immunity, including autoimmunity. We previously demonstrated that CD1d-restricted type II NKT cells, which carry diverse TCRs, prevented T1D in the NOD mouse model for the human disease. In this study, we show that CD4(+) 24αβ type II NKT cells, but not CD4/CD8 double-negative NKT cells, were sufficient to downregulate diabetogenic CD4(+) BDC2.5 NOD T cells in adoptive transfer experiments. CD4(+) 24αβ NKT cells exhibited a memory phenotype including high ICOS expression, increased cytokine production, and limited display of NK cell markers, compared with double-negative 24αβ NKT cells. Blocking of ICOS or the programmed death-1/programmed death ligand 1 pathway was shown to abolish the regulation that occurred in the pancreas draining lymph nodes. To our knowledge, these results provide for the first time cellular and molecular information on how type II CD1d-restricted NKT cells regulate T1D.
Adenoviruses are a major cause of infectious mortality in children following allogeneic hematopoietic stem cell transplantation, with adoptive transfer of adenovirus-specific T cells being an effective therapeutic approach. We have previously shown that T cells specific for the peptide epitope LTDLGQNLLY were protective. In this study, we aimed to establish a viral dissemination assay to measure the antiviral capacity of T cells specific for this and other peptide epitopes in an infectious setting. We used replication-competent adenovirus 11 (Ad11pGFP) and adenovirus 5 containing adenovirus 35 fiber (Ad5F35GFP) viruses and T cells specific for HLA-A*01-restricted LTDLGQNLLY, HLA-B*07-restricted KPYSGTAYNAL, and HLA-A*02-restricted LLDQLIEEV peptide epitopes. T cells in PBMC from healthy donors were expanded with peptide and IL-2 or treated with IL-2 alone to serve as nonstimulated control cells, and then these expanded or nonstimulated CD8(+) cells were purified and cocultured with autologous monocytes infected with adenovirus at low multiplicity of infection. After 3 d, the number of infected GFP(+) monocytes and, hence, viral dissemination was quantified by flow cytometry. T cells expanded with LTDLGQNLLY peptide from multiple HLA-A*01(+) donors prevented adenovirus dissemination, and nonstimulated T cells did not prevent dissemination, thus, indicating that LTDLGQNLLY-specific T cells have high antiviral capacity. Similarly, expanded KPYSGTAYNAL- and LLDQLIEEV-specific T cells could prevent viral dissemination. However, the frequency of expanded T cells specific for these last two epitopes was variable between donors with consequent variable prevention of adenoviral dissemination. Taken together, we demonstrate that T cells specific for three peptide epitopes, from both structural and nonstructural proteins, can prevent adenoviral dissemination and provide a novel method to measure the antiviral capacity of adenovirus-specific T cell responses.
Two types of dendritic cells (DC) are circulating in human blood and can be identified by their differential expression of the myeloid Ag CD11c. In this study, we show that CD11c- peripheral blood (PB)-DC correspond to plasmacytoid DC of lymphoid tissue not only by their surface Ag expression profile but, more impressively, by their peculiar ultramorphology. We also demonstrate that CD11c- and CD11c+ DC differ in the quality of their response to and in their requirement for certain cytokines. Freshly isolated CD11c- cells depend on IL-3 for survival and use autocrine or exogenous TNF-alpha as maturation signal, leading to the appearance of a highly dendritic phenotype, the up-regulation and redistribution of MHC class II from lysosomal compartments to the plasma membrane, the increased expression of costimulatory molecules, and the switch from a high Ag-processing to a low Ag-processing/potent accessory cell mode. Surprisingly, IL-4 efficiently killed freshly isolated CD11c- PB-DC, but did not impair the viability of CD11c+ PB-DC and, together with GM-CSF, induced maturation of these cells. A direct functional comparison revealed that neo-Ag-modified and subsequently matured CD11c- but to a lesser extent CD11c+ DC were able to prime naive Ag-specific CD4+ T cells. Our findings show that two diverse DC types respond to certain T cell-derived cytokines in a differential manner and, thus, suggest that suppression or activation of functionally diverse DC types may be a novel mechanism for the regulation of the quantity and quality of immune responses.
B lymphocytes optimize Ab responses by somatic hypermutation (SH), which introduces pointmutations in the variable regions of the Ab genes and by class-switch recombination (CSR), which changes the expressed C region exon of the IgH. These Ab diversification processes are initiated by the deaminating enzyme activation-induced cytidine deaminase followed by many DNA repair enzymes, ultimately leading to deletions and a high mutation rate in the Ab genes, whereas DNA lesions made by activation-induced cytidine deaminase are repaired with low error rate on most other genes. This indicates an advanced regulation of DNA repair. In this study, we show that initiation of Ab diversification in B lymphocytes of mouse spleen leads to formation of a complex between many proteins in DNA repair. We show also thatBCR activation, which signals the end of successful SH, reduces interactions between some proteins in the complex and increases other interactions in the complex with varying kinetics. Furthermore, we show increased localization of SH-and CSR-coupled proteins on switch regions of the Igh locus upon initiation of SH/CSR and differential changes in the localization upon BCR signaling, which terminates SH. These findings provide early evidence for a DNA repair complex or complexes that may be of functional significance for carrying out essential roles in SH and/or CSR in B cells.
The low precursor frequency of Ag-reactive CD4+ T cells has been a barrier to the study of CD4+ T cell responses to conventional Ags as well as CD4+ T cell responses to autoantigens recognized during the course of an autoimmune disease. We have recently reported that all "conventional Ag" reactive CD4+ T cells are contained within the subpopulation expressing high levels of the CD4 molecule, termed CD4high. We have identified a CD4high population in the islets of Langerhans of prediabetic nonobese diabetic (NOD) mice that is extremely potent in transferring disease. As few as 500 CD4high islet-infiltrating CD4+ T cells transferred insulin-dependent diabetes mellitus to CD8 reconstituted NOD-SCID mice within 30 days of transfer. In contrast, CD4high T cells isolated from either NOD spleen or salivary glands did not transfer insulin-dependent diabetes mellitus into similar CD8-reconstituted NOD-SCID recipients. These data indicate that the precursor frequency of NOD islet-reactive, pathogenic CD4+ T cells is much higher in the prediabetic NOD pancreas than in these other organs. The islet-infiltrating CD4high T cells displayed selected memory markers, by cell surface analysis, and displayed a Th 1 phenotype by RNase protection assay, but had a marked decrease in IL-4 mRNA determined by quantitative real time PCR when compared with the less pathogenic CD4normal islet-infiltrating T cells. Use of the CD4high marker to select Ag activated T cells represents a tool to isolate and study pathogenic CD4+ T cells from autoimmune lesions in which the Ag has not been previously defined.
The mechanisms regulating T lymphocyte migration within the extracellular matrix are not understood. We show in this study that the thrombospondin-1 binding site of calreticulin, spanning aa 19-32, is a major triggering factor for T cell motility and migration within a three-dimensional collagen type 1 matrix, and that exogenous motogenic factors such as chemokines can stimulate migration via a calreticulin-thrombospondin-1 pathway. Endogenous calreticulin binding to the N-terminal domain of endogenous thrombospondin-1 elicited a motogenic signal to the T cells through the C-terminal domain of thrombospondin-1 and its cell surface receptor integrin-associated protein (CD47). Our data further revealed that thrombospondin-1 was expressed on the cell surface with a high turnover, and that PI3K and the Janus family of tyrosine kinases were required for T cell motility mediated through calreticulin, thrombospondin-1, and CD47. These results unveil an autocrine mechanism of calreticulin-thrombospondin-1-CD47 interaction for the control of T cell motility and migration within three-dimensional extracellular matrix substrata.
Type I IFN is a major player in innate and adaptive immune responses. Besides, it is involved in organogenesis and tumor development. Generally, IFN responses are amplified by an autocrine loop with IFN-beta as the priming cytokine. However, due to the lack of sensitive detection systems, where and how type I IFN is produced in vivo is still poorly understood. In this study, we describe a luciferase reporter mouse, which allows tracking of IFN-beta gene induction in vivo. Using this reporter mouse, we reveal strong tissue-specific induction of IFN-beta following infection with influenza or La Crosse virus. Importantly, this reporter mouse also allowed us to visualize that IFN-beta is expressed constitutively in several tissues. As suggested before, low amounts of constitutively produced IFN might maintain immune cells in an activated state ready for a timely response to pathogens. Interestingly, thymic epithelial cells were the major source of IFN-beta under noninflammatory conditions. This relatively high constitutive expression was controlled by the NF Aire and might influence induction of tolerance or T cell development.
C1 inhibitor (C1INH) protects mice from lethal Gram-negative bacterial LPS-induced endotoxin shock and blocks the binding of LPS to the murine macrophage cell line, RAW 264.7, via an interaction with lipid A. Using the cecal ligation and puncture (CLP) model for sepsis in mice, treatment with C1INH improved survival in comparison with untreated controls. The effect was not solely the result of inhibition of complement and contact system activation because reactive center-cleaved, inactive C1INH (iC1INH) also was effective. In vivo, C1INH and iC1INH both reduced the number of viable bacteria in the blood and peritoneal fluid and accelerated killing of bacteria by blood neutrophils and peritoneal macrophages. In vitro, C1INH bound to bacteria cultured from blood or peritoneal fluid of mice with CLP-induced sepsis, but had no direct effect on bacterial growth. However, both C1INH and iC1INH enhanced the bactericidal activity of blood neutrophils and peritoneal exudate leukocytes. C1INH-deficient mice (C1INH-/- mice) subjected to CLP had a higher mortality than did wild-type littermate mice. Survival of C1INH-/- mice was significantly increased with two doses of C1INH, one given immediately following CLP, and the second at 6 h post-CLP. C1INH may be important in protection from sepsis through enhancement of bacterial uptake by, and/or bactericidal capacity of, phagocytes. Treatment with C1INH may provide a useful additional therapeutic approach in some patients with peritonitis and/or sepsis.
Tuning of TCR-mediated activation was demonstrated to be critical for lineage fate in T cell development, as well as in the control of autoimmunity. In this study, we identify a novel diabetes susceptibility gene, Idd28, in the NOD mouse and provide evidence that Cd3zeta (Cd247) constitutes a prime candidate gene for this locus. Moreover, we show that the allele of the Cd3zeta gene expressed in NOD and DBA/2 mouse strains confers lower levels of T cell activation compared with the allele expressed by C57BL/6 (B6), BALB/c, and C3H/HeJ mice. These results support a model in which the development of autoimmune diabetes is dependent on a TCR signal mediated by a less-efficient NOD allele of the Cd3zeta gene.
The functional properties of intraepithelial lymphocytes (IEL) in normal human jejunum, ileum, and colon were investigated. Cytokine mRNA expression in IEL and enterocytes was determined by reverse transcriptase-PCR and IFN-gamma+ IEL by immunohistochemistry. Polyclonal activators were used to study proliferation and IFN-gamma secretion of IEL, and an anti-CD3-mediated redirected cytotoxicity assay was used to determine the lytic potential of IEL. Freshly isolated IEL at all three gut levels expressed mRNA for IL-1 beta, IL-2, IL-8, IFN-gamma, and TNF-alpha. Approximately 10% of IEL produced IFN-gamma, suggesting that IEL are immunologically active in vivo, performing similar functions along the intestine. IEL could be stimulated further in vitro to express IL-10, TNF-beta, and TGF-beta 1, while no Th2-type cytokines were induced, suggesting suppressive and cytolytic functions for IEL. All three jejunal IEL subpopulations (CD4-CD8-TCR-gamma delta+, CD4+TCR-alpha beta+, CD8+TCR-alpha beta+) expressed the same four cytokines, IL-2, IL-8, IFN-gamma, and TNF-alpha, indicating that CD4+TCR-alpha beta+ IEL are Th1 cells and that TCR-gamma delta+ IEL and CD8+TCR-alpha beta+ IEL include cytotoxic effector cells. Indeed, freshly isolated jejunal IEL displayed cytolytic activity. IEL were induced to proliferation by anti-CD3/TCR complex mAbs and leukoagglutinin, but not by Con A. There was no correlation between the magnitude of the proliferative response and the amounts of secreted IFN-gamma. Enterocytes expressed IL-1 beta and IL-8, and sometimes TNF-alpha. Although jejunal enterocytes express HLA-DR and hsp60, Ag presentation by these cells may induce anergy since their cytokine profile is different from that of classical APCs.
We have shown that gamma delta T cells in human gingiva have an intraepithelial location and, that in the chronic inflammatory disease periodontitis, the expression of CD45RO and CD8 or CD4 is induced on gamma delta T cells. To study the role of gamma delta T cells in local antibacterial responses, we determined the cytokine profiles of isolated human gingival cells. Different T cell subpopulations, isolated by positive selection with mAb-coated magnetic beads and macrophages, as well as epithelial cells, were analyzed for expression of mRNA for 15 cytokines by reverse transcriptase-PCR. The ultrastructure of gingival gamma delta T cells was also studied. The gamma delta T cells expressed mRNA for IFN-gamma, TNF-alpha, TGF-beta 1, and IL-6. Expression of IFN-gamma was a consequence of inflammation. CD4+ gamma delta T cells expressed IFN-gamma only, whereas CD8+ gamma delta T cells expressed all four cytokines. CD8+ cells expressing IFN-gamma, TNF-alpha, and IL-6 in combination suggest a cytotoxic effector function. Gingival gamma delta T cells contained cytoplasmic electron-dense membrane-bound granules and multivesicular bodies that are ultrastructural characteristics of cytotoxic cells. Epithelial cells from inflamed gingiva expressed HLA-DR, CD1a, CD1c, and heat shock protein 60 on the cell surface. They also expressed mRNA for IL-1 beta, IL-6, IL-8, TNF-alpha, and TGF-beta 1. Thus, epithelial cells may function as accessory cells in immune activation and, at the same time, be target cells for CD8+ gamma delta T cells reactive with CD1 Ag or heat shock protein. These results suggest that gamma delta T cells constitute a first line of defense in gingiva, preventing entrance of pathogens by cytotoxicity against infected and stressed epithelial cells, and by control of epithelial cell growth through secretion of regulatory cytokines.
Originally limited to basophils and mast cells, the spectrum of high affinity IgE receptor (Fc epsilon RI-bearing cells has expanded recently to include Langerhans cells, dermal dendritic cells (DC), monocytes, and eosinophils. As a result of studies on the distribution, structure, and function of Fc epsilon RI on APCs, we discovered a minor nonbasophil, nonmonocyte PBMC population that can bind IgE via Fc epsilon RI. This receptor occurs on the surface of these cells as a multimeric structure containing Fc epsilon RI alpha- and Fc epsilon RI gamma-chains but, unlike its counterpart on basophils, lacking Fc epsilon RI beta. Further experiments revealed that these Fc epsilon RI alpha gamma-expressing cells closely resemble peripheral blood DC by immunophenotype (HLA-DRhigh, HLA-DQhhigh; CD4+, CD11a+, CD32+, CD33+, B7/2 (CD86)+; CD11blow, CD14low, CD40low, CD54low, CD64low) and cell morphology. These features allowed us to isolate Fc epsilon RI-expressing DC from the peripheral blood and to investigate their immunostimulatory properties. We found Fc epsilon RI-positive DC to be efficient stimulators of both primary (allogeneic MLR) and Fc epsilon RI/IgE-dependent, secondary T cell responses at low cell numbers. Thus, Fc epsilon RI-expressing DC may not only amplify established type I allergic immune reactions but, unlike Fc epsilon RI-positive semiprofessional APCs, may be able to prime naive T cells to common and/or cryptic epitopes of IgE-reactive Ags.
Human decidual lymphocytes from early, normal pregnancy were characterized in situ with respect to ultrastructure and distribution of subsets. The ultrastructure of isolated decidual gamma delta T cells was also studied. CD45+ cells comprised 11 +/- 2% of all decidual cells. The majority were localized in large lymphoid cell clusters (LCC), near endometrial glands, or as intraepithelial lymphocytes (IEL) in glandular epithelium. The major cell populations in LCC were CD56+TCR-gamma delta+ cells, CD56+ cells, TCR-alpha beta+CD4+ cells, and TCR-alpha beta+CD8+ cells. All expressed activation markers (CD45RO, Kp43, and/or HML-1) and MHC class II Ag (HLA-DR, HLA-DP, and/or HLA-DQ). No B cells were found. Almost all IEL were activated TCR-gamma delta+ cells (CD56+ and CD56-). The glandular epithelial cells expressed heat shock protein 60 at the basolateral side facing the TCR-gamma delta+ IEL. Decidual lymphocytes displayed cytoplasmic processes, microvilli, characteristic cytoplasmic granules, and had intimate contact with neighboring cells. Lymphocytes in the outer rim of LCC and the stroma showed signs of cellular movement. Two main morphotypes of gamma delta T cells could be distinguished. One had single microvilli, membrane-bound granules, and nuclear inclusions. The other had many microvilli, nonmembrane-bound granules and cytoplasmic multivesicular bodies. Our data suggest that LCC are centers of immune reactivity where T and NK cells become activated. The activated cells may guard against infections and undue trophoblast invasion and/or be involved in modulating the local maternal immune system toward unresponsiveness against the semiallogeneic fetus.
The mononuclear lymphoid cell population in human pregnant uterus mucosa, decidua, from early normal pregnancies was studied phenotypically and functionally. The phenotype was determined in situ by immunohistochemistry, and in isolated decidual mononuclear cell preparations by immunofluorescence and flow cytometry. A mild isolation procedure of gentle mechanical disruption followed by density gradient centrifugation was used. Leukocytes comprised a large part of the decidual tissue. They were present in aggregates mainly situated adjacent to the glandular epithelium. In addition, individual leukocytes were present intraepithelially, as well as scattered between the stromal cells and around vessels and lacunes. Four lymphocyte populations of approximately the same size were identified: TCR gamma delta+/CD56+ cells, TCR gamma delta+/CD56- cells, TCR gamma delta-/CD56+ cells, and TCR alpha beta+/CD8+ cells. TCR gamma delta- expressing cells comprised about 60% of the T cells. They were CD4-/CD8-, and about half of the TCR gamma delta+ cells expressed the memory/activation marker CD45RO. The Kp 43 Ag, earlier described on activated CD56+ and TCR gamma delta+ cells in peripheral blood, was essentially only expressed on the TCR gamma delta-/CD56+ cell population in decidua. At least 50% of the TCR alpha beta+ cells were CD8+. The function(s) of either one of these populations might be to prevent immunologic reactions against the fetus, to protect the uterus from unwanted extensive invasion of trophoblasts, or to protect the uteroplacental unit from infection. Decidual T cells did not respond to stimulation by alloantigens or mitogenic anti-CD3 mAb but responded to the same extent as PBMC to mitogenic lectins. The surface density of the TCR/CD3 complex was low on freshly isolated decidual lymphocytes, but could be up-regulated upon stimulation with PMA/Ionomycin. Local selective down-regulation of surface expression of the TCR/CD3 complex and of activation involving this complex might be one of the mechanisms by which a maternal immunologic reaction against the semiallogeneic fetus is prevented.
The uterine mucosa in pregnancy, the decidua, allows placenta formation and survival of the fetus despite the fact that it is semiallogeneic. Decidua contains large numbers of lymphocytes, of which CD56+ cells dominate, followed by T cells expressing either alpha beta or gamma delta TCR. We have investigated the developmental relationship between the CD56- and TCR gamma delta-expressing cells in early pregnancy decidua using dual labeling immunoelectron microscopy, immunoflow cytometry, and cell fractionation. Lymphocyte subpopulations were, in addition, analyzed for expression of the cytokine receptor for IL-7 and c-kit and for mRNA expression of recombinase-activating genes 1 and 2. Four different cell populations could be distinguished: CD56+bright, CD56+dim/TCR gamma delta+low, CD56+dim/TCR gamma delta+high, and TCR gamma delta+low. Recombinase-activating genes 1 and 2 were expressed in the CD56+bright cells and to a limited degree in CD56+dim/TCR gamma delta+low cells. c-kit was preferentially expressed on the CD56+bright cells, while IL-7R was preferentially expressed on CD56+dim/TCR gamma delta+low and CD56+dim/TCR gamma delta+high cells. The CD56+dim TCR gamma delta+low and CD56+dim/TCR gamma delta+high cells displayed the characteristic morphology of large granular lymphocytes, while single positive TCR gamma delta+low cells were usually smaller and did not contain cytoplasmic granules. The gamma delta 1 gene segment was almost exclusively used in the TCR. Gamma delta T cells in mitosis were seen. We suggest that human early pregnancy decidua is a transient site for extrathymic maturation and that the progenitors of TCR gamma delta+ cells are bone marrow-derived immature cells expressing the CD56 (neural cell adhesion molecule) homing receptor.
Src homology 2 domain-containing protein tyrosine phosphatase (SHP) substrate-1 (SHPS-1) is a transmembrane protein that is expressed predominantly in macrophages. Its extracellular region interacts with the transmembrane ligand CD47 expressed on the surface of adjacent cells, and its cytoplasmic region binds the protein tyrosine phosphatases SHP-1 and SHP-2. Phagocytosis of IgG- or complement-opsonized RBCs by peritoneal macrophages derived from mice that express a mutant SHPS-1 protein that lacks most of the cytoplasmic region was markedly enhanced compared with that apparent with wild-type macrophages. This effect was not observed either with CD47-deficient RBCs as the phagocytic target or in the presence of blocking Abs to SHPS-1. Depletion of SHPS-1 from wild-type macrophages by RNA interference also promoted FcgammaR-mediated phagocytosis of wild-type RBCs. Ligation of SHPS-1 on macrophages by CD47 on RBCs promoted tyrosine phosphorylation of SHPS-1 and its association with SHP-1, whereas tyrosine phosphorylation of SHPS-1 was markedly reduced in response to cross-linking of FcgammaRs. Treatment with inhibitors of PI3K or of Syk, but not with those of MEK or Src family kinases, abolished the enhancement of FcgammaR-mediated phagocytosis apparent in macrophages from SHPS-1 mutant mice. In contrast, FcgammaR-mediated tyrosine phosphorylation of Syk, Cbl, or the gamma subunit of FcR was similar in macrophages from wild-type and SHPS-1 mutant mice. These results suggest that ligation of SHPS-1 on macrophages by CD47 promotes the tyrosine phosphorylation of SHPS-1 and thereby prevents the FcgammaR-mediated disruption of the SHPS-1-SHP-1 complex, resulting in inhibition of phagocytosis. The inhibition of phagocytosis by the SHPS-1-SHP-1 complex may be mediated at the level of Syk or PI3K signaling.
IL-6, leukemia inhibitory factor (LIF), and oncostatin M (OSM) are IL-6-type cytokines that stimulate osteoclast formation and function. In the present study, the resorptive effects of these agents and their regulation of receptor activator of NF-kappaB ligand (RANKL), RANK, and osteoprotegerin (OPG) were studied in neonatal mouse calvaria. When tested separately, neither human (h) IL-6 nor the human soluble IL-6R (shIL-6R) stimulated bone resorption, but when hIL-6 and the shIL-6R were combined, significant stimulation of both mineral and matrix release from bone explants was noted. Semiquantitative RT-PCR showed that hIL-6 plus shIL-6R enhanced the expression of RANKL and OPG in calvarial bones, but decreased RANK expression. Human LIF, hOSM, and mouse OSM (mOSM) also stimulated 45Ca release and enhanced the mRNA expression of RANKL and OPG in mouse calvaria, but had no effect on the expression of RANK. In agreement with the RT-PCR analyses, ELISA measurements showed that both hIL-6 plus shIL-6R and mOSM increased RANKL and OPG proteins. 1,25-Dihydroxyvitamin D3 (D3) also increased the RANKL protein level, but decreased the protein level of OPG. OPG inhibited 45Ca release stimulated by RANKL, hIL-6 plus shIL-6R, hLIF, hOSM, mOSM, and D3. An Ab neutralizing mouse gp130 inhibited 45Ca release induced by hIL-6 plus shIL-6R. These experiments demonstrated stimulation of calvarial bone resorption and regulation of mRNA and protein expression of RANKL and OPG by D3 and IL-6 family cytokines as well as regulation of RANK expression in preosteoclasts/osteoclasts of mouse calvaria by D3 and hIL-6 plus shIL-6R.
Increasing evidence implicates HSV type 1 (HSV1) in the pathogenesis of late-onset Alzheimer disease (AD). HSV1 has evolved highly sophisticated strategies to evade host immunosurveillance. One strategy involves encoding a decoy Fcγ receptor (FcγR), which blocks Fc-mediated effector functions, such as Ab-dependent cellular cytotoxicity. Ig γ marker (GM) allotypes, encoded by highly polymorphic IGHG genes on chromosome 14q32, modulate this immunoevasion strategy, and thus may act as effect modifiers of the HSV1-AD association. In this nested case-control human study, 365 closely matched case-control pairs-whose blood was drawn on average 9.6 y before AD diagnosis-were typed for GM alleles by a TaqMan genotyping assay. APOE genotype and a genetic risk score based on nine additional previously known AD risk genes (ABCA7, BIN1, CD33, CLU, CR1, EPHA1, MS4A4E, NECTIN2, and PICALM) were extracted from a genome-wide association study analysis. Antiviral Abs were measured by ELISA. Conditional logistic regression models were applied. The distribution of GM 3/17 genotypes differed significantly between AD cases and controls, with higher frequency of GM 17/17 homozygotes in AD cases as compared with controls (19.8 versus 10.7%, p = 0.001). The GM 17/17 genotype was associated with a 4-fold increased risk of AD (odds ratio 4.142, p < 0.001). In conclusion, the results of this study demonstrate that Ig GM 17/17 genotype contributes to the risk of later AD development, independent of apolipoprotein ε4 genotype and other AD risk genes, and explain, at least in part, why every HSV1-infected person is not equally likely to develop HSV1-associated AD.
Cerebral malaria is the most severe complication of Plasmodium falciparum infection and accounts for a large number of malaria fatalities worldwide. Recent studies demonstrated that C5(-/-) mice are resistant to experimental cerebral malaria (ECM) and suggested that protection was due to loss of C5a-induced inflammation. Surprisingly, we observed that C5aR(-/-) mice were fully susceptible to disease, indicating that C5a is not required for ECM. C3aR(-/-) and C3aR(-/-) × C5aR(-/-) mice were equally susceptible to ECM as were wild-type mice, indicating that neither complement anaphylatoxin receptor is critical for ECM development. In contrast, C9 deposition in the brains of mice with ECM suggested an important role for the terminal complement pathway. Treatment with anti-C9 Ab significantly increased survival time and reduced mortality in ECM. Our data indicate that protection from ECM in C5(-/-) mice is mediated through inhibition of membrane attack complex formation and not through C5a-induced inflammation.
The NOD mouse is an important experimental model for human type 1 diabetes. T cells are central to NOD pathogenesis, and their function in the autoimmune process of diabetes has been well studied. In contrast, although recognized as important players in disease induction, the role of B cells is not clearly understood. In this study we characterize different subpopulations of B cells and demonstrate that marginal zone (MZ) B cells are expanded 2- to 3-fold in NOD mice compared with nondiabetic C57BL/6 (B6) mice. The NOD MZ B cells displayed a normal surface marker profile and localized to the MZ region in the NOD spleen. Moreover, the MZ B cell population developed early during the ontogeny of NOD mice. By 3 wk of age, around the time when autoreactive T cells are first activated, a significant MZ B cell population of adult phenotype was found in NOD, but not B6, mice. Using an F2(B6 x NOD) cross in a genome-wide scan, we map the control of this trait to a region on chromosome 4 (logarithm of odds score, 4.4) which includes the Idd11 and Idd9 diabetes susceptibility loci, supporting the hypothesis that this B cell trait is related to the development of diabetes in the NOD mouse.
The molecular basis for formation of lymphoid follicle and its homeostasis in the secondary lymphoid organs remains unclear. Signal regulatory protein α (SIRPα), an Ig superfamily protein that is predominantly expressed in dendritic cells or macrophages, mediates cell-cell signaling by interacting with CD47, another Ig superfamily protein. In this study, we show that the size of the T cell zone as well as the number of CD4(+) T cells were markedly reduced in the spleen of mice bearing a mutant (MT) SIRPα that lacks the cytoplasmic region compared with those of wild-type mice. In addition, the expression of CCL19 and CCL21, as well as of IL-7, which are thought to be important for development or homeostasis of the T cell zone, was markedly decreased in the spleen of SIRPα MT mice. By the use of bone marrow chimera, we found that hematopoietic SIRPα is important for development of the T cell zone as well as the expression of CCL19 and CCL21 in the spleen. The expression of lymphotoxin and its receptor, lymphotoxin β receptor, as well as the in vivo response to lymphotoxin β receptor stimulation were also decreased in the spleen of SIRPα MT mice. CD47-deficient mice also manifested phenotypes similar to SIRPα MT mice. These data suggest that SIRPα as well as its ligand CD47 are thus essential for steady-state homeostasis of T cells in the spleen.
Apoptosis is crucially important in mediating immune privilege of the fetus during pregnancy. We investigated the expression and in vitro apoptotic activity of two physiologically relevant death messengers, the TNF family members Fas ligand (FasL) and TRAIL in human early and term placentas. Both molecules were intracellularly expressed, confined to the late endosomal compartment of the syncytiotrophoblast, and tightly associated to the generation and secretion of placental exosomes. Using immunoelectron microscopy, we show that FasL and TRAIL are expressed on the limiting membrane of multivesicular bodies where, by membrane invagination, intraluminal microvesicles carrying membranal bioactive FasL and TRAIL are formed and released in the extracellular space as exosomes. Analyzing exosomes secreted from placental explant cultures, to our knowledge, we demonstrate for the first time that FasL and TRAIL are clustered on the exosomal membrane as oligomerized aggregates ready to form death-inducing signaling complex. Consistently, placental FasL-and TRAIL-carrying exosomes triggered apoptosis in Jurkat T cells and activated PBMC in a dose-dependent manner. Limiting the expression of functional FasL and TRAIL to exosomes comprise a dual benefit: 1) storage of exosomal FasL and TRAIL in multivesicular bodies is protected from proteolytic cleavage and 2) upon secretion, delivery of preformed membranal death molecules by exosomes rapidly triggers apoptosis. Our results suggest that bioactive FasL-and TRAIL-carrying exosomes, able to convey apoptosis, are secreted by the placenta and tie up the immunomodulatory and protective role of human placenta to its exosome-secreting ability.
We have analyzed the V-gene usage in gamma delta T cells of the human gut and joint by using a new mAb (B18) specific for V gamma 8 of human TCR-gamma delta+ T cells. The B18+ population constituted a minor subset of the gamma delta T cells in peripheral blood (PB) of healthy persons (6 +/- 5%) and only 1 of 35 gamma delta T cell clones analyzed was positive. In contrast, the B18+ subset was a dominant gamma delta T cell population among intraepithelial lymphocytes (IEL) derived from the human intestine (74 +/- 29, p < 0.002), and two of three IEL clones from patients with coeliac disease were B18+. Interestingly, a higher proportion of B18+ gamma delta T cells was found in the synovial fluid of patients with rheumatoid arthritis (RA) (21 +/- 18%, 0.02 < p < 0.05) compared with normal PB. Furthermore, the B18+ subset was more frequent among IL-2-expanded gamma delta T cells (42 +/- 20%) derived from synovial tissue than among IL-2-expanded cells derived from synovial fluid (p < 0.002) and PB from RA patients (p < 0.02) as well as normal PB (p < 0.002). The V-gene usage of 13 gamma delta T cell clones from the synovial fluid of arthritic patients was analyzed. All B18+ clones (n = 7) expressed mRNA for V gamma 8 together with mRNA for V delta 1 (n = 5) or mRNA for V delta 3 (n = 2). None of the B18- clones expressed V gamma 8 (n = 6). We conclude that the gamma delta T cell that expresses V gamma 8, together with mainly V delta 1, is a major gamma delta T cell subset among the IEL of the gut and a highly frequent subset in the synovial tissue of patients with RA. This subset may correspond to the mouse V gamma 7+ IEL, which has a high degree of amino acid sequence homology with the human V gamma 8 protein.
A protective and anti-inflammatory role for CD1d-dependent NKT cells (NKTs) has been reported in experimental and human autoimmune diseases. However, their role in arthritis has been unclear, with conflicting reports of CD1d-dependent NKTs acting both as regulatory and disease-promoting cells in arthritis. These differing modes of action might be due to genetic differences of inbred mice and incomplete backcrossing of gene-modified mice. We therefore put special emphasis on controlling the genetic backgrounds of the mice used. Additionally, we used two different murine arthritis models, Ag-induced arthritis (AIA) and collagen-induced arthritis (CIA), to evaluate acute and chronic arthritis in CD1d knockout mice and mice depleted of NK1.1(+) cells. CD1d-deficient mice developed more severe AIA compared with wild-type littermates, with a higher degree of inflammation and proteoglycan depletion. Chronic arthritis in CIA was also worse in the absence of CD1d-dependent NKTs. Elevated levels of Ag-specific IFN-gamma production accompanied these findings rather than changes in IL-17alpha. Depletion of NK1.1(+) cells supported these findings in AIA and CIA. This report provides support for CD1d-dependent NKTs being suppressor cells in acute and chronic arthritis, likely via inhibition of arthritogenic Th1 cells. These results make CD1d-dependent NKTs an attractive target for therapeutic intervention.
Nontypeable Haemophilus influenzae (NTHi) is a Gram-negative human pathogen that causes infections mainly in the upper and lower respiratory tract. The bacterium is associated with bronchitis and exacerbations in patients suffering from chronic obstructive pulmonary disease and frequently causes acute otitis media in preschool children. We have previously demonstrated that the binding of C4b binding protein (C4BP) is important for NTHi complement evasion. In this study, we identified outer membrane protein 5 (P5) of NTHi as a novel ligand of C4BP. Importantly, we observed significantly lower C4BP binding and decreased serum resistance in P5-deficient NTHi mutants. Surface expression of recombinant P5 on Escherichia coli conferred C4BP binding and consequently increased serum resistance. Moreover, P5 expression was positively correlated with C4BP binding in a series of clinical isolates. We revealed higher levels of P5 surface expression and consequently more C4BP binding in isolates from the lower respiratory tract of chronic obstructive pulmonary disease patients and tonsil specimens compared with isolates from the upper respiratory tract and the bloodstream (invasive strains). Our results highlight P5 as an important protein for protecting NTHi against complement-mediated killing.
Because NF-kappaB signaling pathways are highly conserved in evolution, the fruit fly Drosophila melanogaster provides a good model to study these cascades. We carried out an RNA interference (RNAi)-based genome-wide in vitro reporter assay screen in Drosophila for components of NF-kappaB pathways. We analyzed 16,025 dsRNA-treatments and identified 10 novel NF-kappaB regulators. Of these, nine dsRNA-treatments affect primarily the Toll pathway. G protein-coupled receptor kinase (Gprk)2, CG15737/Toll pathway activation mediating protein, and u-shaped were required for normal Drosomycin response in vivo. Interaction studies revealed that Gprk2 interacts with the Drosophila IkappaB homolog Cactus, but is not required in Cactus degradation, indicating a novel mechanism for NF-kappaB regulation. Morpholino silencing of the zebrafish ortholog of Gprk2 in fish embryos caused impaired cytokine expression after Escherichia coli infection, indicating a conserved role in NF-kappaB signaling. Moreover, small interfering RNA silencing of the human ortholog GRK5 in HeLa cells impaired NF-kappaB reporter activity. Gprk2 RNAi flies are susceptible to infection with Enterococcus faecalis and Gprk2 RNAi rescues Toll(10b)-induced blood cell activation in Drosophila larvae in vivo. We conclude that Gprk2/GRK5 has an evolutionarily conserved role in regulating NF-kappaB signaling.
Signaling from the BCR is used to judge Ag-binding strengths of the Abs of B cells. BCR signaling enables the selection for successive improvements in the Ag affinity over an extremely broad range of affinities during somatic hypermutation. We show that the mouse BCR is subject to general negative feedback regulation of the receptor proteins, as well as many coreceptors and proteins in signal pathways from the receptor. Thus, the BCR can downregulate itself, which can enable sensitive detection of successive improvements in the Ag affinity over a very large span of affinities. Furthermore, the feedback inhibition of the BCR signalosome and most of its proteins, as well as most other regulations of genes by BCR stimulation, is to a large extent through inhibition of the transcription factor E2A by Ca(2+)/calmodulin.
It is widely established that mast cells (MCs) have a harmful role in asthma, for example by secreting various proinflammatory substances stored within their secretory granule. However, in this study, we show that one of the substances stored within MC granule, chymase, in fact has a protective role in allergic airway inflammation, indicating that MCs may possess both harmful and protective activities in connection with this type of disease. Wild-type (WT) mice and mice lacking mouse MC protease 4 (mMCP-4), a chymase that is functionally homologous to human chymase, were sensitized and challenged with OVA, followed by the assessment of airway physiology and inflammatory parameters. Our results show that the airway hyperresponsiveness was significantly higher in mMCP-4(-/-) as compared with WT mice. Moreover, the degree of lung tissue inflammation was markedly higher in mice lacking mMCP-4 than in WT controls. Histological analysis revealed that OVA sensitization/challenge resulted in a marked increased in the thickness of the smooth muscle cell (SMC) layer and, notably, that the degree of SMC layer thickening was more pronounced in mMCP-4(-/-) animals than in WT controls, thus indicating that chymase may have an effect on airway SMCs. In support of this, mMCP-4-positive MCs were located in the close vicinity of the SMC layer, mainly in the upper airways, and mMCP-4 was shown to be the major chymase expressed in these MCs. Taken together, our results indicate that chymase present in the upper airways protects against allergic airway responses, possibly by regulating SMCs.
CD47 is a ligand of the inhibitory receptor, signal regulatory protein (SIRP)alpha, and its interaction with SIRPalpha on macrophages prevents phagocytosis of autologous hematopoietic cells. CD47-SIRPalpha signaling also regulates dendritic cell (DC) endocytosis, activation, and maturation. In this study, we show that CD47 expression on donor cells plays an important role in suppression of allograft rejection by donor-specific transfusion (DST). DST was performed by i.v. injection of splenocytes from C57BL/6 donors into MHC class I-disparate bm1 mice 7 d prior to donor skin grafting. Administration of wild-type (WT) C57BL/6 donor splenocytes markedly prolonged donor skin survival in bm1 mouse recipients. In contrast, bm1 mice receiving DST from CD47 knockout (KO) donors showed no inhibition or even acceleration of donor skin graft rejection compared with non-DST control (naive) bm1 mice. T cells from bm1 mice receiving CD47 KO, but not WT, DST exhibited strong anti-donor responses. The ability of DST to suppress alloresponses was positively correlated with the density of CD47 molecules on donor cells, as CD47(+/-) DST was able to prolonged donor skin survival, but to a significantly less extent than WT DST. Furthermore, DCs from CD47 KO, but not WT, DST recipients showed rapid activation and contributed to donor skin rejection. These results show for the first time that CD47 on donor cells is required to repress recipient DC activation and suppress allograft rejection after DST, and suggest CD47 as a potential target for facilitating the induction of transplant tolerance.
The E-proteins E2A, HeLa E-box binding protein, and E2-2 constitute a class of basic helix-loop-helix transcription factors that differentially affect B cell development. E2A is by far the most investigated and appears to operate at several levels during B cell ontogeny. Less is known concerning the role of the other E-proteins. To address the role of E2-2, we have performed transfers of fetal liver (FL) cells into irradiated Rag-deficient mice. Although the transfer of E2-2-deficient cells alone can reconstitute all B cell subpopulations, albeit with a moderate reduction in cellularity, E2-2-deficient cells have a disadvantage when transferred together with wild-type cells. Cultivation of E2-2(-/-) day 14.5 FL cells on stromal cells and IL-7 revealed a reduced frequency of responding B cell progenitors despite normal IL-7Ralpha surface expression. Real-time PCR analysis revealed that E2-2 mRNA expression is high at the pro-B cell stage and drops sharply at the pre-B cell stage, consistent with a role for E2-2 in pro-B cells. In contrast, E2A mRNA was most abundant in pre-B cells. Analysis of the peripheral repertoire revealed that mice reconstituted with E2-2(-/-) FL cells had an increased proportion of marginal zone (MZ) B cells. Interestingly, E2-2 mRNA was elevated approximately 2-fold (p < 0.01) in follicular compared with MZ B cells. Although E2A mRNA showed a similar tendency, the difference was not significant. Collectively, our findings indicate that E2-2 is required for optimal expansion of pro-B cells, and also influences the follicular vs MZ decision.
In Drosophila melanogaster larvae, three classes of circulating cellular immune surveillance cells (hemocytes) can be identified: plasmatocytes, crystal cells, and lamellocytes. Plasmatocytes are profiessional phagocytes most similar to the mammalian monocyte/macrophage lineage and make up similar to 95% of circulating hemocytes. The other similar to 5% of circulating hemocytes consists of crystal cells, which secrete components necessary for the melanization of invading organisms, as well as for wound repair. A third cell type known as lamellocytes are rarely seen in healthy larvae and are involved in the encapsulation of invading pathogens. There are no obvious mammalian counterparts for crystal cells or lamellocytes, and there is no equivalent to the lymphoid lineage in insects. In this review, I will discuss what is currently known about Drosophila hemopoiesis and the cellular immune response and where possible compare it to vertebrate mechanisms.
The immune processes associated with atherogenesis have received considerable attention during recent years. IgG FcRs (FcgammaR) are involved in activating the immune system and in maintaining peripheral tolerance. However, the role of the inhibitory IgG receptor FcgammaRIIB in atherosclerosis has not been defined. Bone marrow cells from FcgammaRIIB-deficient mice and C57BL/6 control mice were transplanted to low-density lipoprotein receptor-deficient mice. Atherosclerosis was induced by feeding the recipient mice a high-fat diet for 8 wk and evaluated using Oil Red O staining of the descending aorta at sacrifice. The molecular mechanisms triggering atherosclerosis was studied by examining splenic B and T cells, as well as Th1 and Th2 immune responses using flow cytometry and ELISA. The atherosclerotic lesion area in the descending aorta was ~5-fold larger in mice lacking FcgammaRIIB than in control mice (2.75 +/- 2.57 versus 0.44 +/- 0.42%; p < 0.01). Moreover, the FcgammaRIIB deficiency resulted in an amplified splenocyte proliferative response to Con A stimulation (proliferation index 30.26 +/- 8.81 versus 2.96 +/- 0.81%, p < 0.0001) and an enhanced expression of MHC class II on the B cells (6.65 +/- 0.64 versus 2.33 +/- 0.25%; p < 0.001). In accordance, an enlarged amount of CD25-positive CD4 T cells was found in the spleen (42.74 +/- 4.05 versus 2.45 +/- 0.31%; p < 0.0001). The plasma Ab and cytokine pattern suggested increased Th1 and Th2 immune responses, respectively. These results show that FcgammaRIIB inhibits the development of atherosclerosis in mice. In addition, they indicate that absence of the inhibiting IgG receptor cause disease, depending on an imbalance of activating and inhibiting immune cells.
Type I IFNs play a key role in linking the innate and adaptive arms of the immune system. Although produced rapidly in response to pathogens, IFNs are also produced at low levels in the absence of infection. In the present study, we demonstrate that constitutively produced IFNs are necessary in vivo to maintain dendritic cells in an "Ag presentation-competent" state. Conventional dendritic cells (cDCs) isolated from spleens of IFN-beta or IFNAR-deficient mice exhibit a highly impaired ability to present Ag and activate naive T cells. Microarray analysis of mRNA isolated from IFN-beta(-/-) and IFNAR(-/-) cDCs revealed diminished expression of two genes that encoded members of the heat shock protein 70 (Hsp70) family. Consistent with this observation, pharmacological inhibition of Hsp70 in cDCs from wild-type mice impaired their T cell stimulatory capacity. Similarly, the Ag presentation ability of splenic cDCs isolated from Hsp70.1/3(-/-) mice was also severely impaired in comparison to wild-type cDCs. Thus, constitutive IFN-beta expression regulates Hsp70 levels to help maintain dendritic cells in a competent state for efficient priming of effector T cells in vivo.