HLA-B SPECIFICITIES AND W4, W6 SPECIFICITIES ARE ON SAME POLYPEPTIDE

The human alloantigenic specificities w4 and w6, which are products of a diallelic system genetically associated with the HL-A-B locus, were solubilized by papain digestion of membranes from the lymphoblastoid cell line, RPMI 4265. The w4 and w6 specificities copurified with the HL-A-B locus products, HL-A-B7 and HL-A-B12. Sequential immunoprecipitation experiments were performed using alloantisera to HL-A-B7, HL-A-B12, w4 and w6 and a purified HL-A-B7, B12, w4, w6 antigen pool labeled with 125I-Bolton-Hunter reagent. HL-A-B7 and w6, which are genetically associated with each other, are different antigenic determinants on the same molecule, while HL-A-B12 and w4, also genetically associated, are distinct antigenic determinants on a 2nd molecule. The HL-A-B determinants and w4, w6 determinants are apparently on the same polypeptide. The genetic implications of the findings are discussed.