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Background/Purpose: Increased levels of TH17 and TH22 as well as TC17 and TC22 cells have previously been associated with ankylosing spondylitis (AS). The correlation between these inflammatory T cell subsets and clinically relevant parameters as well as cytokines has also been reported. However, the status of these inflammatory cells in a well characterized AS cohort from northern Sweden has not been studied. The purpose of this study was to confirm the increased presence of inflammatory T cell subsets in peripheral blood of patients with AS from northern Sweden in relation to age and sex-matched controls. In addition, associations of clinically relevant parameters with the level of the inflammatory T cell subset(s) and cytokines of interest were performed.

Methods: Peripheral blood mononuclear cells (PBMCs) from a cohort of 50 patients with AS from Region Västerbotten (Modif NY, mean age 52±9.1 years, 33 (66 %) men, 50 (100 %) HLAB27) and 50 pair wise matched blood donor controls (mean age 54±8.8 years, 33 (66 %) men) were stained with a combination of antibodies allowing for the detection of surface expressed CD45, CD3, CD4, CD8, intracellular IL-17 and IL-22 and analyzed by flow cytometry. In addition, levels of IL-17 and IL-22 in plasma were determined by the Meso Scale Discovery platform. The patient with AS were examined with spinal x-ray for radiographic alterations assessed with mSASSS. CRP and ESR were measured and physical function and disease activity were registered with BASMI and BASFI respectively ASDAS-CRP and BASDAI.

Results: Pair wise comparison of AS patients and controls showed a 1,5 to 2-fold increase of TH17, TH22 and TC22 cells among CD45+CD3+ lymphocytes in PBMCs of male patients (p=0,013, p=0,003 and p=0,024 respectively). Levels of IL-22 in plasma and proportion of TC17 correlated in male patients (Rs=0,499 p=0,003) and plasma levels of IL10 showed an inverse correlation in relation to TC17 in all patients (Rs=-0,276 p=0,05). In female AS patients there was a negative correlation between TC22 and CRP (Rs = -0,573, p=0,016). In addition, after splitting the group of female into pre- and postmenopausal correlation between TC17 and mSASSS (Rs = 0,845, p=0,034), TC22 and BASFI (Rs = 0,986, p=0,0003) (premenopausal) and TC22 and BASMI (Rs = 0,764, p=0,006) (postmenopausal) was observed.

Conclusion: We confirm an increased proportion of TH17, TH22 and TC17 cells in blood in AS male patients from northern Sweden. In addition, positive correlation of the proinflammatory cytokine IL-22 and negative correlation of anti-inflammatory cytokine IL-10 in relation to TC17 corroborate the influence of these cells in the disease process. Interestingly, in female AS patients there was a correlation between clinical relevant parameters to particular inflammatory T cell subset dependent on the menopausal status, suggesting a role of female sex hormones in AS pathogenesis.