Underexpression of TIM-3 and Blunted Galectin-9-Induced Apoptosis of CD4+ T Cells in Rheumatoid Arthritis

The aim of this study is to compare the expression of TIM-3 from CD4+ T cells from rheumatoid arthritis (RA) patients and healthy controls and to evaluate the effect of galectin-9 (Gal-9) on apoptosis of CD4+ T cells in these patients. CD4+ T cells from RA patients and healthy controls were isolated from peripheral blood mononuclear cells and were activated. The expression of TIM-3 mRNA in CD4+ T cells was measured using real-time polymerase chain reaction. CD4+ T cells were activated in the presence of graded doses of Gal-9 or control, and Gal-9-induced cytotoxicity and apoptotic activity of CD4+ T cells were analyzed using MTT assays and annexin-V staining, respectively. TIM-3 mRNA expression was significantly lower in CD4+ T cells from RA patients compared with those in healthy controls (p = 0.028). CD4+ T cell survival as measured by MTT assay when incubated with Gal-9 (15 nM) was significantly higher in RA patients than in healthy controls (p = 0.002). Apoptotic activity of CD4+ T cells from healthy controls as measured by annexin staining increased with graded doses of Gal-9 (0 nM vs. 30 nM, 0 nM vs. 90 nM, p = 0.016 each). However, apoptotic activity of CD4+ T cells from RA patients did not change despite the stimulation with Gal-9. Gal-9-mediated apoptosis of CD4+ T cells is dysfunctional in RA patients. Blunted Gal-9-mediated apoptosis may be exerted through underexpression of TIM-3 that negatively regulates Th1 response. Our data suggest that TIM-3 and its interaction with Gal-9 may play an important role in the pathogenesis of RA and may represent a potential therapeutic target.