Class-I MHC-restricted T cell associated molecule (CRTAM) is a receptor that is primarily expressed on activated cytotoxic lymphocytes, where it may play a role in their adhesion, interaction or migration. It is one of the most highly expressed surface markers detected on activated human NK T cells and CD8 T cells, suggesting its use as a diagnostic tool in various human viral and autoimmune diseases. CRTAM binds nectin-like protein 2 (necl2), which is involved in IL-22 expression regulation. This Necl2/CRTAM molecular pair may regulate cell/cell interactions and may play a role in neuronal interactions. CRTAM is also highly expressed in Purkinje neurons in the cerebellum.