T-cell immunoglobulin mucin 3, a transmembrane glycoprotein and member of the immunoglobulin superfamily, is preferentially expressed by differentiated CD4+ Th1 cells and CD8+ Tc1 (cytotoxic) cells, but not by CD4+ Th2 cells or CD8+ Tc2 cells. Tim-3 acts as a negative regulator of Th1-mediated inflammatory diseases including GVHD, type I diabetes, and EAE (experimental autoimmune encephamyelitis), promotes immunological tolerance, and is a receptor for galectin-9, shown to induce cell death of Th1 cells in vitro. Tim-3 is also involved in the regulation of macrophage activation, acts as a phagocytic receptor, and has been shown to recognize apoptotic cells via the IgV domain. Studies have shown Tim-3 significantly inhibits the efficient phagocytosis of apoptotic cells by PEMs (peritoneal exudate Mac1+ cells) (Nakayama et al. 2009).