ROLE OF HLA-B-ASTERISK-5101 BINDING NONAMER PEPTIDES IN FORMATION OF THE HLA-BW4 PUBLIC EPITOPE

HLA-Bw4 is one of two HLA-B public epitopes which are discriminated by specific alloantisera and mAb. It is believed that the residues 77-83 of HLA-B molecules form the Bw4 epitope recognized by specific antibo dies. This epitope is also recognized by NKB1 receptors on NK cells. W e investigated the role of a peptide bound to HLA-B molecules on the f ormation of the Bw4 epitope recognized by two HLA-Bw4-specific mAb, TU 109 and TU48, which recognized the difference of the Bw4 epitope among HLA-B51, -B52 and -B53. Recognition of the HLA-B5101-peptide complex by these mAb was examined using a panel of HLA-B5101 binding nonamer peptides. The sequence of HLA-B5101 binding peptides has a minimum i nfluence on the binding of TU48 mAb to HLA-B5101 molecules. In contra st, the binding of TU109 mAb to HLA-B5101 molecules was critically in fluenced by the sequence of a peptide bound to HLA-B5101 molecules. T U109 mAb did not recognize HLA-B5101 binding peptides carrying small or negatively charged residues at P8. The results were confirmed by a panel of mutant peptides at P8. Taken together, these results indicate that a positively charged or neutralized side chain of P8 is critical for the epitope formation of Bw4 recognized by this mAb.