Analysis of PD-1 and Tim-3 expression on CD4⁺ T cells of patients with rheumatoid arthritis; negative association...

Expression of T cell immunoglobulin and mucin-domain containing-3 (Tim-3) and programmed cell death-1 (PD-1) was studied on CD4⁺ T cells of patients with rheumatoid arthritis (RA). Association of Tim-3 and PD-1 expression with disease activity of RA patients was also addressed. A total of 37 RA patients and 31 sex- and age-matched healthy controls were included in this study. Disease activity of RA patients was determined by Disease Activity Score of 28 joints scoring system (DAS28). A three-color flow cytometry method was applied to determine the frequency of Tim-3⁺/PD-1⁺/CD4⁺ T cells. To measure the cytokine production, peripheral blood mononuclear cells (PBMCs) were stimulated with PMA/ionomycin. Concentrations of IL-17, IL-10, IFN-γ, and TNF-α were measured in culture supernatants by ELISA. The frequency of PD-1⁺/CD4⁺ and Tim-3⁺/PD-1⁺/CD4⁺ T cells was significantly higher in patients with RA compared to that in controls (p = 0.0013 and p = 0.050, respectively). The percentage of Tim-3⁺/CD4⁺ T cells was similar in patients and controls (p = 0.4498). The RA patients have produced significant higher levels of TNF-α, IL-17, and IFN-γ than those of healthy controls (p = 0.0121, p = 0.0417, and p = 0.0478, respectively). Interestingly, an inverse correlation was found between the frequency of Tim-3⁺/CD4⁺ cells and DAS28 of RA patients (r = - 0.4696, p = 0.0493). Similarly, the percentage of Tim-3⁺/PD-1⁺/CD4⁺ T cells was also revealed an inverse correlation with DAS28 (r = - 0.5268, p = 0.0493). Moreover, significant positive correlations were detected between the concentrations of TNF-α (r = 0.6418, p = 0.0023) and IL-17 (r = 0.4683, p = 0.0373) with disease activity of RA patients. Our results indicate that Tim-3 and PD-1 are involved in immune dysregulation mechanisms of rheumatoid arthritis and could be considered as useful biomarkers for determination of disease activity and progression.