Mapping of the monoclonal antibody W6/32:: sensitivity to the amino terminus of β2-microglobulin

The monoclonal antibody W6/32 is one of the most commonly used pan-HLA-ABC antibodies in studying human MHC I structure and function. We have discovered that the reactivity of W6/32 is absolutely sensitive to the amino terminus of human beta(2)-microglobulin (h beta(2)m). Bacterially expressed recombinant forms of h beta(2)m that have been extensively used in structural and biochemical studies of MHC I molecules often have an additional methionine at their amino terminus. Cell surface MHC I molecules reconstituted with allele-specific peptides and recombinant h beta(2)m are reactive with Various HLA-specific mAbs, but not W6/32. In contrast, cell surface HLA molecules reconstituted with peptide and native h beta(2)m, which has no amino terminal methionine, are recognized by W6/32 as well as other HLA-specific mAbs. Thus, the specificity of W6/32 includes the amino terminus of h beta(2)m.