Murine Ia and human DR antigens were isolated and purified by immunoprecipitation and sodium dodecyl sulfate/polyacrylamide gel electrophoresis with allo- and xenoantisera, respectively. The I-A subregion antigen consists of two chains, designated Aα, and Aβ, with molecular weights of 35.000 and 26.000, respectively. The I-C subregion antigen likewise consists of two chains, designated Cα and Cβ, with molecular weights of 32.000 and 29.000, respectively. Under nonreducing conditions, the Cβ chain migrates appreciably more rapidly on sodium dodecyl sulfate/polyacrylamide gels than the reduced Cβ chain, reflecting the presence of an intra-chain disulfide bond. The human DR antigen is also a two-chain unit and contains DRα and DRβ components with molecular weights of 34.000 and 28.000, respectively. The DRβ chain migrates more rapidly before reduction than afterward, like the murine Cβ chain. The DRβ and Cβ chains are also strikingly homologous if a single amino acid shift is imposed on one of those chains. Thus, human DR antigens strongly resemble the murine I-C subregion antigens.
ASJC Scopus subject areas