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Intra-epithelial lymphocytes. Evidence for regional specialization and extrathymic T cell maturation in the human gut epithelium
Umeå University, Faculty of Medicine, Department of Clinical Microbiology, Immunology/Immunchemistry.
Umeå University, Faculty of Medicine, Department of Clinical Microbiology, Clinical Immunology.
Umeå University, Faculty of Medicine, Department of Clinical Microbiology, Immunology/Immunchemistry.
Umeå University, Faculty of Medicine, Department of Surgical and Perioperative Sciences, Surgery.
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1995 (English)In: International Immunology, ISSN 0953-8178, E-ISSN 1460-2377, Vol. 7, no 9, 1473-1487 p.Article in journal (Refereed) Published
Abstract [en]

The human gut epithelium is a unique immunological compartment, containing substantial amounts of intra-epithelial lymphocytes (IEL) with unknown functions. In this study we show that distinct and unusual subpopulations of IEL are present at different levels of human intestine. IEL phenotypes in normal jejunum, ileum and colon were compared using immunoflow cytometry and immunohistochemistry. The expression of mRNA for recombination-activating gene-1 (RAG-1) in IEL from all three levels was compared using reverse-transcription polymerase chain reaction, and the morphology of IEL in situ was determined using immunoelectron microscopy. Surface marker profiles of isolated intestinal epithelial cells at all three levels were also investigated. On average the proportion of TCR gamma delta IEL was comparable in jejunum than ileum and colon and varied in phenotype with gut level. CD4-CD8-TCR alpha beta IEL dominated in colon but were absent in jejunum. CD8+ TCR alpha beta IEL were present at all levels but only in jejunum did they constitute the majority of all IEL. CD4+ TCR alpha beta IEL were present in similar frequencies at all levels of the gut. In general, the majority of IEL had an activated phenotype (CD45RO+, alpha E beta 7+). Furthermore, IEL exhibited phenotypes which are rare in peripheral blood. The thymocyte markers CD1a and CD1c as well as the NK cell marker CD56 were expressed on a fraction of TCR alpha beta and TCR gamma delta IEL. A small population of 'null' cells (CD45+ TCR/CD#-CD20-CD14-CD15- cells) was also present at equal proportions along the gut. Jejunal but not colonic IEL expressed RAG-1 mRNA suggesting that extrathymic T cell maturation occurs in the epithelium of small intestine. RAG-1 was expressed in CD2+TCR/CD3- and CD3+/TCR-IEL. Ultrastructurally, IEL often formed small clusters and intimate contacts with epithelial cells, suggesting cell cooperation within the epithelium. Some IEL had pseudopodium-like extensions penetrating the epithelial basement membrane suggesting transmigration. Epithelial cells in small intestine but not colon expressed heat shock protein 60 and HLA-DR. CD1a, CD1b and CD1c were not expressed on intestinal epithelial cells at any level. The distinct surface marker profiles of IEL and epithelial cells along small and large intestine suggest functional regional specialization and are compatible with the hypothesis that TCR alpha beta IEL participate in immune reactions to lumenal antigens while TCR gamma delta IEL perform surveillance of the epithelium.

Place, publisher, year, edition, pages
1995. Vol. 7, no 9, 1473-1487 p.
National Category
URN: urn:nbn:se:umu:diva-67898DOI: 10.1093/intimm/7.9.1473PubMedID: 7495755OAI: diva2:614791
Available from: 2013-04-07 Created: 2013-04-07 Last updated: 2013-08-08Bibliographically approved
In thesis
1. Human intraepithelial lymphocytes: a comparative study of phenotype, morphology, and functional properties of intraepithelial lymphocytes in gut and oral mucosa
Open this publication in new window or tab >>Human intraepithelial lymphocytes: a comparative study of phenotype, morphology, and functional properties of intraepithelial lymphocytes in gut and oral mucosa
1995 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Human intraepithelial lymphocytes (IEL) constitute a unique cell population situated in the first line of defense of the alimentary tract. Here they are continuously exposed to a massive antigenic load of high complexity. However, different conditions prevail along the alimentary tract. In small intestine food antigens dominate whereas bacterial antigens are abundant in large intestine. The oral cavity is exposed to an enormous variety of antigens from the microflora as well as food constituents. The abundance and selective localization of lymphocytes in the surface epithelium of these challenged tissues implicate important roles for IEL in immune protection.

IEL in normal human jejunum, ileum and colon as well as in normal and chronically inflamed gingiva were studied in situ and after isolation, with regard to phenotype, ultrastructure, cytokine mRNA expression and response to T-cell mitogens. Furthermore, an isolation technique was developed which yielded highly purified, functionally active IEL and enterocytes from the same sample.

Intestinal IEL were situated in the basal part of the epithelium, often in small clusters and in close contact with adjacent lymphocytes and epithelial cells. They had an irregular shape with long processes and some had pseudopodium-like extensions penetrating the basement membrane. This indicates cell co-operation within the epithelium, as well as transmigration of IEL to underlying tissues. Freshly isolated IEL expressed several cytokines (IL-1β, IL-8, IL-2, TNF-α and IFN-γ) and in vitro activation induced expression of IL-2, IL-10, IFN-γ, TNF-α, TNF-β and TGF-β1, suggesting that IEL are involved in cell mediated cytotoxicity and suppressor cell activities.

γδ T cells showed preferential homing to the epithelium both in gingiva and in intestine. They constituted the major lymphocyte population in normal gingiva and on average 30% of IEL at all levels of the intestine. Gingival as well as intestinal γδ IEL showed preferential usage of Vδ1Vγ8, suggesting common reactivity patterns along the alimentary tract. Intestinal γδ IEL and γδ IEL in normal gingiva were CD4-CD8-. In contrast, γδ IEL in chronically inflamed gingiva were predominantly CD8+ and showed induced expression of CD45RO. This indicates that γδ IEL participate in anti-bacterial immune responses in mucosa. Intestinal and gingival γδ IEL displayed ultrastructural features of cytolytic effector cells, e.g. electron-dense cytoplasmic granules and multivesicular bodies. They also expressed cytokines indicative of cell mediated-cytolytic effector functions. γδ IEL from inflamed gingiva expressed IFN-γ, TNF-α, TGF-β1 and IL-6 mRNA while intestinal γδ IEL expressed IL-2, IFN-γ and TNF-α.

Intraepithelial αβ T cells were rare in gingiva while they constituted the major population of intestinal IEL. The phenotype of αβ IEL varied at different levels of the intestine. Thus, CD8+αβ IEL dominated in jejunum while cells with the unusual T-cell phenotype, CD4-CD8- TCR αβ+, constituted a major population of colonic IEL. CD4+ αβ IEL were equally represented, as a minor population, at all three levels of the gut. Intestinal αβ IEL had the same cytokine profile as γδ IEL. Taken together, these data suggest that αβ IEL are involved in immunoregulatory responses to luminal antigens.

IEL with thymocyte-like phenotyped (CD2+TCR/CD3-, CD1+TCR/CD3-, CD1+TCRαβ+ and CD1+TCRγδ+) were present in jejunal epithelium. Furthermore, recombination activating gene-1 (RAG-1) mRNA was expressed in CD2+TCR/CD3- and CD3+/TCR- jejunal IEL. RAG-1 was not expressed in colonic IEL. Thus, the epithelium of small intestine is a site for extrathymic T cell maturation in humans.

Place, publisher, year, edition, pages
Umeå: Umeå universitet, 1995. 71 p.
Umeå University odontological dissertations, ISSN 0345-7532 ; 50
human intraepithelial lymphocytes, alimentary tract, intestinal epithelium, gut luminal antigens, gingiva, γδ T cells, immunoelectron microscopy, cytokine mRNA, RT-PCR, extrathymic T cell maturation, RAG-1, periodontitis, mucosal immune system, CD4-CD8- αβ T cells, CD8+ γδ T cells
National Category
Immunology in the medical area
urn:nbn:se:umu:diva-79123 (URN)91-7174-997-7 (ISBN)
Public defence
1995-03-10, Major Groove, by 6L, Umeå universitet, Umeå, 09:00
Available from: 2013-08-08 Created: 2013-08-08 Last updated: 2013-08-08Bibliographically approved

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