Description
MHC class I polypeptide-related sequence B; also known as MICB; is a heavily glycosylated protein serving as a ligand for the type II receptor NKG2D. MICB shares 85% amino acid identity with MICA; a closely related protein; both of which contain three extracellular immunoglobulin-like domains; but without capacity to bind peptide or interact withbeta-2-microglobulin. acting as a stress-induced self-antigen; binding of MICB to the NKG2D receptor activates the cytolytic response of natural killer (NK) cells; CD8+alphabeta T cells; and gammadelta T cells on which the receptor is expressed. MICA/B are minimally expressed on normal cells; but are frequently expressed on epithelial tumors and can be induced by bacterial and viral infections. MICA/B recognition thus is involved in tumor surveillance; viral infections; and autoimmune diseases