T cell immunoglobulin mucin-3 (TIM-3) is a member of the T-cell Immunoglobulin- and Mucin-domain-containing family of type I membrane glycoproteins that regulate autoimmune and allergic disease. TIM-3 is selectively expressed on Th1 cells and interacts with galectin-9. It negatively regulates Th1 responses and affects macrophage activation. The 280 amino acid mature human TIM-3 contains a V-type Ig-like domain that shows multiple polymorphisms, followed by a mucin-like domain in the 171 amino acid extracellular region, which shares 60% amino acid identity with mouse TIM-3 ECD.