T cell immunoglobulin and mucin domain-3 (Tim-3), also known as HAVCR2, is a member of the TIM family of immune regulatory molecules and a type I transmembrane glycoprotein with a molecular weight of 60 kD. T cell immunoglobulin and mucin domain-3 (Tim-3), also known as HAVCR2, is a member of the TIM family of immune regulatory molecules and a type I transmembrane glycoprotein with a molecular weight of 60 kD. Mature Tim-3 consists of 181aa extracellular domain, 21aa transmembrane domain, and 78aa cytoplasmic domain. Tim-3 is an important member of the T cell immunoglobulin molecular family and a key molecule that regulates CD4+CD25+regulatory T (TR) cells expressed by activated Th1 cells. Th1 cells express full-length membrane type Tim3 (flTim3) and soluble type Tim3 (sTim3) through mRNA selective splicing. Tim-3 is mainly expressed in differentiated and mature Th1 cells, and when combined with its ligand galactin-9, it can downregulate the immune response of Th1 type cells.