Analysis of the interaction of peptide hen egg white lysozyme (34-45) with the I-A(k) molecule

We examined the structural characteristics of a peptide Ag that determine its ability to interact with class II-MHC molecules and TCR. The studies reported here focused on recognition of the hen egg white lysozyme (HEL) tryptic fragment HEL(34-45) by two I-A(k)-restricted T cell hybridomas. HEL(34-45) bound to I-A(k) created more than one antigenic specificity. Experiments with truncated peptides and alanine-substituted peptides indicated that two T cell hybrids either recognized distinct regions of the HEL(34-45) peptide, or different determinants generated by interaction of the peptide with I-A(k). Although we identified residues of HEL(34-45) that were critical to T cell recognition, no positions in the peptide were identified as I-A(k) contact sites using single alanine substitutions. This suggest that more than one site or region of the peptide contributes to the binding I-A(k). Finally, the murine lysozyme equivalent of 34-45 did not bind to I-A(k). Substitution of the corresponding murine lysozyme (self) residue at position 41 of HEL(34-45) abrogated I-A(k) binding of the peptide.