HLA-B specificities and w4, w6 specificities are on the same polypeptide.

The human alloantigenic specificities w4 and w6, which are products of a diallelic system genetically associated with the HLA-B locus, have been solubilized by papain digestion of membranes from the lymphoblastoid cell line, RPMI 4265. The w4 and w6 specificities copurified with the HLA-B locus products, HLA-B7 and HLA-B12. Sequential immunoprecipitation experiments were performed using alloantisera to HLA-B7, HLA-B12, w4 and w6, and a purified HLA-B7, B12, w4, w6 antigen pool labeled with 125I-Bolton-Hunter reagent. These experiments demonstrated directly that HLA-B7 and w6, which are genetically associated with each other, are different antigenic determinants on the same molecule, while HLA-B12 and w4, also genetically associated, are distinct antigenic determinants on a second molecule. Arguments are presented which suggest that the HLA-B determinants and w4, w6 determinants are in fact on the same polypeptide, and the genetic implications of the findings are discussed.