TIM-4 is a type I membrane protein belonging to the TIM family of cell surface receptors that regulate Th1 and Th2 cell responses. The extracellular region of TIM-4 has an RGD containing V-type Ig-like domain and a serine/threonine-rich mucin domain. Unlike other TIM family members, its intracellular tail lacks tyrosine-phosphorylation motifs. TIM-4 is a ligand for TIM-1, which is also known as hepatitis A virus cellular receptor (HAVCR). The extracellular domain of human TIM-4 shares 53% amino acid sequence identity with that of mouse TIM-4.