Elevated frequency of IL-37- and IL-18Rα-positive T cells in the peripheral blood of rheumatoid arthritis patients.

OBJECTIVE: To detect the expression of IL-37 and its receptors IL-18Rα and IL-1R8 in CD4+ T cells and total lymphocytes in rheumatoid arthritis (RA) patients and the relationship between autoantibodies and disease activity. To investigate the mechanism of IL-37 and its receptors involved in the pathogenesis of RA. To evaluate the effects of different concentrations of rhIL-37 on peripheral blood mononuclear cells (PBMCs) in RA patients with TNF-α, and IL-6. METHODS: The expression of IL-37 and its receptor IL-18Rα and IL-1R8 in peripheral blood CD4+ T cells and total lymphocytes in RA patients and healthy controls were measured by flow cytometry. The levels of TNF-α and IL-6 in the supernatant were measured by ELISA after rhIL-37 stimulation with PBMCs. RESULTS: The expression of IL-37 and IL-18Rα in the total lymphocytes, especially in CD4+ T cells in RA patients, was significantly higher than in the healthy control group. There was a positive correlation between the frequency of IL-37- or IL-18Rα-positive CD4+ T cells and ESR, CRP, and DAS28 values. Additionally, rhIL-37 significantly down-regulated TNF-α and IL-6 production in RA patients' PBMCs. CONCLUSIONS: IL-37 plays an important role in the regulation of inflammation in RA. IL-37 and its receptors may play an immunoregulatory role in the activation of lymphocytes, especially CD4+ T cells, in RA patients. IL-37 may represent a therapeutic target for rheumatoid arthritis.