HLA serological cross-reactivity: HLA-B15 has two public antigens

On the basis of their serologic cross-reactivity, HLA antigens can be organized into cross-reactive groups or CREG's. We have recently defined immunochemically two public alloantigenic determinants X and Y which can account for the serological cross-reactivity of the B7-CREG and B5-CREG, respectively. One of the smaller of these CREG's consists of HLA-B15 and B17. Using microcytotoxicity testing, a fluoresceinated Protein A binding assay, and chemical immunoprecipitation techniques, we have defined a new public alloantigenic determinant, tentatively designated "Z," which is present on the 44,000 dalton glycoprotein chains of HLA-B15 and HLA-B17, but distinct from the B15 and B17 determinants. Since HLA-B15 is also a member of the B5-CREG, and therefore bears allodeterminant Y, this report constitutes the first immunochemical demonstration of two public determinants, Y and Z, on a single HLA-B molecule, HLA-B15.