Novel insights into Tim-4 function in autoimmune diseases.

T-cell immunoglobulin domain and mucin domain-4 (Tim-4) was first recognized as a costimulatory molecule regulating T-cell activation. Dysregulation of Tim-4 has been found in some autoimmune conditions, particularly in the immune cells. Recently, Tim-4 was found to be critical for regulating T cells, with the ability of inhibiting naïve CD4(+) T cells and Th17 cells, increasing Th2 cell development. Tim-4 can also enhance T cell expansion via linker for activation of T cells, extracellular signal-regulated kinase (ERK) and Protein kinase B (PKB, also known as Akt) signaling pathways. Moreover, the Tim-4 signaling pathway may affect multiple molecular processes in autoimmune diseases. A number of previous studies have demonstrated that Tim-4 influences chronic autoimmune diseases, such as rheumatoid arthritis (RA) and systemic lupus erythematosus. In addition, an association between Tim-4 polymorphisms and susceptibility to several autoimmune diseases have been identified, such as RA. Taken together, recent works have indicated that Tim-4 may represent a novel target for the treatment of autoimmune diseases. In this article, we will discuss the Tim-4 function and the therapeutic potential of modulating the Tim-4 in autoimmune diseases.