Objective: To assess the association between serum levels of IL-37 in rheumatoid arthritis patients and percentage of peripheral blood T lymphocytes expressing the activation marker CD26 and investigate their correlation with disease activity.
Methods: The study included 48 rheumatoid arthritis patients and 42 age and sex matched healthy controls. Serum levels of IL-37 were determined using enzyme linked immunosorbent assay while percentage of CD3+CD26+T cells in peripheral blood mononuclear cells was assayed using flowcytometry.
Results: Serum levels of IL-37, as well as the percentage of CD3+CD26+T cells, were significantly higher in rheumatoid arthritis patients than in healthy controls. Also, serum IL-37 levels were higher in patients with severe disease activity than patients with moderate and low disease activity. In rheumatoid arthritis patients, both serum levels of IL-37 and percentage of CD3+CD26+T cells correlated with disease activity (DAS28), C-reactive protein levels and erythrocyte sedimentation rate. In addition, serum levels of the anti-inflammatory cytokine IL-37 positively correlated with the percentage of CD3+CD26+T cells in peripheral blood of rheumatoid arthritis patients.
Conclusion: Our results indicate a strong correlation between serum levels of IL-37 and frequency of activated T cells in peripheral blood of rheumatoid arthritis patients. Our results suggest that in an active disease status, activated T lymphocytes may be a contributing source to the elevated levels of IL-37 trying to down-regulate the active inflammatory process.
Keywords: CD26; IL-37; Rheumatoid arthritis; T lymphocytes.
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