Demonstration of two distinct light chains in HLA‐DR‐associated antigens by two‐dimensional gel electrophoresis

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Abstract
The polypeptide composition of HLA-DR-associated antigens was analyzed by two-dimensional nonequilibrium pH gradient electrophoresis (NEPHGE)/sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis (PAGE). Glycoprotein fractions from B lymphoblastoid cell lines homozygous for the DR antigen were used as antigen source. The HLA-DR-associated antigens were isolated by immunoprecipitation using a monoclonal anti-DR antibody, TDR31.1. Two polypeptides corresponding in molecular weight to the HLA-DR-associated antigen β chain were detected. These polypeptides were shown to be different molecules on the basis of their separation on NEPHGE/SDS-PAGE analysis, their rates of turnover relative to the other polypeptides of the HLA-DR-associated antigens, and their noncoordinate alteration in position on NEPHGE/SDS-PAGE two-dimensional analysis of different cell lines. Of the two β polypeptides, only one was invariant in position on NEPHGE/SDS-FAGE analyses of cell lines homozygous for the same DR specificity. It appears therefore that the position of one of these β polypeptides correlates with DR specificity, while the other β polypeptide exhibits positional variation on NEPHGE/SDS-PAGE analysis, indicative of polymorphism at a second HLA-DR-associated locus.