TIM-3 Genetic Variations Affect Susceptibility to Osteoarthritis by Interfering with Interferon Gamma in CD4+ T Cells.

Osteoarthritis (OA) is the most common type of arthritis, in which T cell responses and cytokines may play critical roles in the development of the disease. TIM-3 may affect immune responses and is correlated with decreased expression of interferon gamma (INF-γ) in CD4+ T cells. In the current study, we investigated the association between polymorphisms in the TIM-3 gene and susceptibility to OA. Two polymorphisms in TIM-3, -574G/T and +4259T/G polymorphisms, were identified in OA cases and healthy donors by polymerase chain reaction-restriction fragment length polymorphism method. Data revealed that the prevalence of TIM-3 +4259T/G genotype was significantly elevated in OA patients than in the healthy donors after adjustment (Odds ratio [OR] = 2.67, 95% confidence interval [CI] 1.32-5.11, P < 0.001). Similarly, the TIM-3 +4259G allele presented a positive association with the risk of OA after adjustment (OR = 2.58, 95% CI 1.29-4.82, P = 0.003). The TIM-3 -574G/T polymorphism did not show any correlation with the disease. We further examined whether the two TIM-3 polymorphisms could affect INF-γ expression in CD4+ T cells. Data revealed that subjects carrying polymorphic +4259TG genotype had significantly higher mRNA and protein levels of INF-γ in CD4+ T cells compared to wild-type GG genotype (P < 0.001 and P < 0.01). These results indicated that TIM-3 polymorphism is associated with increased susceptibility to OA possibly by upregulating INF-γ expression in CD4+ T cells.

Expression of TIM-3 on CD4+ and CD8+ T cells in the peripheral blood and synovial fluid of rheumatoid arthritis.

Rheumatoid arthritis (RA) is characterized by a chronic inflammatory process that targets the synovial lining of diarthrodial joints. TIM-3 plays a key role in the negative regulation of the immune response. In this study, we investigated the expression of TIM-3 on CD4+ and CD8+ T cells from systemic (peripheral blood) and local (synovial fluid) perspectives of RA. Level of TIM-3+ cells from peripheral blood and synovial fluid of patients as well as peripheral blood of healthy controls was measured by flow cytometry. Results showed that TIM-3 expression was significantly increased in both CD4+ and CD8+ T cells in the peripheral blood of RA (p < 0.001 and p < 0.001, respectively). Furthermore, patients revealed even higher expression of TIM-3 in CD4+ and CD8+ T cells in synovial fluid than in peripheral blood. When comparing TIM-3 level with the severity of RA, we identified that the percentage of TIM-3 on both peripheral CD4+ and peripheral CD8+ T cells was negatively correlated with disease activity score 28 (DAS28) of the patients. Similarly, TIM-3 on synovial fluid CD4+ and CD8+ T cells also revealed inverse correlation with DAS28 of the cases. Our data demonstrate a negative correlation between TIM-3 and the disease progression of RA.

Expression of programmed death-1 (PD-1) on CD4+ and CD8+ T cells in rheumatoid arthritis.

Rheumatoid arthritis (RA) is characterized by chronic inflammatory process that targets the synovial lining of diarthrodial joints. Programmed death 1 (PD-1) plays a key role in the negative regulation of the immune response. In the current study, we investigated the expression of PD-1 on peripheral CD4+ and CD8+ T cells in RA patients. Percentage of PD-1+ cells was measured by flow cytometry in 82 RA cases and 90 healthy controls. Results showed that PD-1 expression was significantly decreased in both peripheral CD4+ and CD8+ T cells in RA (p = 0.002 and p < 0.001, respectively). Similarly, serum levels of soluble PD-1 were also downregulated in RA cases. When comparing PD-1 level in RA patients with different clinical parameters, patients with positive C-reactive protein (CRP) revealed lower proportion of PD-1 on CD4+ and CD8+ T cells than those with negative CRP. Also, disease activity score of RA patients was inversely correlated with PD-1 expression on peripheral CD4+ and CD8+ T cells. These data suggested that PD-1 may act as a negative regulator in the pathogenesis and progression of RA.