Cytotoxic and regulatory T-cell molecule, also known as Class-I MHC-restricted T-cell-associated molecule and CRTAM, is a single-pass type I membrane protein which belongs to the nectin family. CRTAM contains one Ig-like C2-type (immunoglobulin-like) domain and one Ig-like V-type (immunoglobulin-like) domain. In the immune system, the expression of CRTAM is restricted to activated class-I MHC-restricted cells, including NKT and CD8 cells. It is strongly expressed in spleen, thymus, small intestine, peripheral blood leukocyte, and in purkinje neurons in cerebellum. It is expressed at much lower levels in testis, ovary, colon, lung and lymphoid tissues. CRTAM is a member of the immunoglobulin superfamily that complies with the structural characteristics of the JAM family of proteins and is phylogenetically more closely related to nectin-like proteins. It is a molecule involved in epithelial cell adhesion.