Structure and biosynthesis of histocompatibility antigens (H-2, HLA)

Abstract

Histocompatibility antigens (H-2K, D and L, and HLA-A, B and C) are highly polymorphic cell surface proteins. Their primary structure has been determined by sequencing the protein, complementary DNAs (cDNAs) or genes in several laboratories. H-2L d and K d antigens are encoded by eight separate exons: one encodes the signal sequence, three encode the external domains, one encodes the membrane spanning segment and three encode the cytoplasmic domain. A similar structural organization has been found for an HLA gene. H-2 and HLA antigens are synthesized on membrane-bound ribosomes and are co-translationally inserted into the membrane of the endoplasmic reticulum. Here they assemble with β 2 -microglobulin, a small secretory protein. We describe the structure, the membrane insertion in vitro and in vivo , the intracellular transport and the surface expression of these antigens.