Molecular structure of human histocompatibility antigens: the HLA‐C series

The HLA‐CW2 antigen of the B lymphoblastoid cell line BRI 8 is structurally homologous to the HLA‐A and B antigens as judged by various criteria. Each antigen comprised a glycosylated polypeptide of 43 000 molecular weight that is noncovalently associated with β₂–microglobulin (β₂ m). Some small differences in molecular parameters were, however, revealed. Thus, the deoxycholate‐solubilized HLA‐CW2 antigen sedimented at the same rate as the HLA‐A antigens but at a slightly faster rate than the HLA‐B antigens. This variation is apparently due to different amounts of bound deoxy‐cholate. Also, whereas essentially all of the HLA‐A and B antigens and about half of the HLA‐CW2 antigen were adsorbed Strongly by Lens culinaris lectin‐Sepharose, the remaining HLA‐CW2 antigen was bound much more weakly and did not require sugar for elution. This difference reflects some structural heterogeneity in the carbohydrate moiety of the HLA‐CW2 antigen. The results of various studies suggest that the HLA‐CW2 antigen is expressed to a lower extent than the HLA‐A or B antigens and that essentially all of the β₂ m of the BRI 8 plasma membrane is associated with the HLA‐A, B and C alloantigenic polypeptides.