Interaction of TIM4 and TIM3 induces T helper 1 cell apoptosis.

The T helper 1 (Th1) polarization plays a critical role in the pathogenesis of a number of inflammatory disorders in the body; the remedies in the correction of polarized Th1 cells are limited. This study aims to investigate the role of T cell immunoglobulin mucin domain molecule 4 (TIM4) in the induction of Th1 cell apoptosis. In this study, polarized Th1 cells were generated from naive Th1 cells from the mouse spleen. Recombinant TIM4 was added to the culture to stimulate the polarized Th1 cells. The apoptosis of Th1 cells was assessed by flow cytometry. The expression of FasL was analyzed by chromatin immunoprecipitation, real time RT-PCR, and Western blotting. The results showed that the polarized Th1 cells expressed high levels of TIM3. After exposure of the polarized Th1 cells to TIM4 in the culture, a complex of TIM3 and TIM4 was detected on the surface of Th1 cells, which induced the Th1 cell apoptosis. The engagement of TIM3 by TIM4 increased p300 phosphorylation in Th1 cells, which further increased the levels of Fas ligand in the cells and induced Th1 cell apoptosis. In conclusion, TIM4 binds TIM3 on the surface of polarized Th1 cells to induce Th1 cell apoptosis, which may contribute to the development of Th2-dominant immune disorders.