HLA-A2-BINDING PEPTIDES CROSS-REACT NOT ONLY WITHIN THE A2 SUBGROUP BUT ALSO WITH OTHER HLA-A-LOCUS ALLELIC PRODUCTS

Seven A2-binding peptides were tested by the HLA class I alpha-chain r efolding assay previously described for their direct binding to HLA cl ass I alpha chains derived from a panel of 18 HLA-homozygous B-cell li nes of various HLA specificities, including four A2 subtypes: A0201, A0204, A*0205, and A*0206. All but one test peptide possessed the maj or anchor residue motifs, L-V, L-L, or I-L, of A2(A0201)/A2(A*0205)-b inding peptides or the closely related motifs, I-V or V-V. This cell p anel analysis confirmed the high A2 allele specificity of the test pep tides, but also revealed the existence of a broad cross-binding within the A2 subgroup. Most peptides bound to the alpha chains of the A2 su btypes tested, although their binding patterns showed differences. Fur thermore, the A2-binding peptides carrying the I-V or V-V motif were f ound to cross-react also outside of the A2 subtypes, probably with A24 , A26, A28, and A29. Other A-locus allelic products, A1, A3, A22, A30, and A31, and the B-locus allelic products carried by the cells tested were essentially negative, although a few exceptions were seen.