Human Major Histocompatibility Complex Class I Antigens: Residues 61-83 of the HLA-B7 Heavy Chain Specify an Alloreactive Site

A chemically synthesized peptide (Asp-Arg-Asn-Thr-Gln-Ile-Tyr-Lys-Ala-Gln-Ala-Gln-Thr-Asp-Arg-Glu-Ser-Leu-Ar g- Asn-Leu-Arg-Gly), homologous to residues 61-83 of the HLA-B7 heavy chain, induced antibodies that specifically recognized the HLA heavy chain-β2-microglobulin complex and the free heavy chain of the HLA-B7 antigen. These antibodies specifically immunoprecipitated the HLA-B7 β2-microglobulin complex solubilized from human lymphoblastoid cells by nonionic detergents and reacted with free HLA-B7 heavy chains in blots on nitrocellulose. These observations suggest that the antigenic conformation of this region of the HLA-B7 molecule is independent of the presence of β2-microglobulin and that amino acid residues 61-83 mimic an alloreactive site expressed by the HLA-B7 antigen.