HLA-DP2 - SELF-PEPTIDE SEQUENCES AND BINDING-PROPERTIES

Although self peptides bound to HLA-DQ and, especially, HLA-DR allotyp es have been described in some detail, few ligands that bind to HLA-DP have been identified. Toward this aim, naturally processed peptides w ere isolated from immunoaffinity-purified HLA-DP2 molecules expressed in cultured B lymphocytes. The size distribution of the peptide repert oire is generally similar to those reported for self peptides bound to HLA-DR and HLA-DQ molecules. Twelve peptides representing individual sequences including two nested sets were sequenced by mass spectrometr y and/or N-terminal Edman analysis. Source proteins included MHC molec ules and other integral membrane proteins as well as secretory and ser um proteins. No dominant amino acid markers suggestive of particular e nzymatic processing events were detected. Peptide specificity and affi nity were examined in binding assays using synthetic peptides and puri fied HLA-DP and HLA-DR molecules. Anchor residues were tentatively ass igned using alanine-substituted analogues of two self peptides. Some s tructural features of HLA-DP2 that may relate to peptide binding are c onsidered.