| description | A heterodimeric membrane protein composed of two non-covalently linked alpha and beta polypeptide chains, both major histocompatibility complex (MHC)-encoded. Each MHC molecule consists of an extracellular peptide-binding cleft followed by an immunoglobulin (Ig)-like domain and transmembrane and cytoplasmic domains. The amino-terminal alpha-1 and beta-1 segments interact to form the peptide-binding cleft Expressed on professional antigen presenting cells, displays peptides derived from endocytosed proteins for recognition by CD4-positive helper T cells. By scanning MHC II molecules, CD4-positive T cells activate effector mechanisms that eliminate extracellular microbes |
