Primary structure of human class II histocompatibility antigens (HLA-D). II. Separation of alpha from beta-chains of HLA-D from a homozygous lymphoblastoid B cell line, H2LCL (HLA-A3,3;B7,7;Dw2,2;MT1,1;DC1,1;MB1,1), and characterization of the isolated chain

In a previous communication we described the preparation of the alpha/beta-chain complex of HLA-D membrane antigens from a homozygous lymphoblastoid B cell line, H2LCL (HLA-A3,3; B7,7; Dw2,2; DR2,2; MT1,1; DC1,1; MB1,1). In this paper we present the separation of the alpha- and beta-chains in quantitative scale using hydroxylapatite chromatography with a pH 7.15 phosphate buffer, containing sodium dodecyl sulfate. An alternative isolation procedure is electrophoresis, taking advantage of the different isoelectric points of the alpha- and beta-chains. The relative molecular masses, the isoelectric points and the N-terminal sequences are discussed and compared with the results of other investigators. Remarkable is the polymorphism of both the chains, especially the beta-chains. The importance of the previously described three step purification procedure for the preparation of these antigens for sequence studies has been pointed out.