title: Fine specificity of murine class II-restricted T cell clones for synthetic peptides of influenza virus hemagglutinin. Heterogeneity of antigen interaction with the T cell and the Ia molecule.
abstract: We have previously demonstrated diversity in the specificity of murine, H-2k class II-restricted, T cell clones for the hemagglutinin (HA) molecule of H3N2 influenza viruses and have mapped two T cell determinants, defined by synthetic peptides, to residues 48-68 and 118-138 of HA1. In this study we examine the nature of the determinant recognized by six distinct P48-68-specific T cell clones by using a panel of truncated synthetic peptides and substituted peptide analogs. From the peptides tested, the shortest recognized were the decapeptides, P53-62 and P54-63, which suggests that the determinant was formed from the 9 amino acids within the sequence 54-62. Asn54 was critical for recognition since P49-68 (54S) was not recognized by the T cell clones. Furthermore this peptide analog was capable of competing with P48-68 for Ag presentation, thereby suggesting that residue 54 is not involved in Ia interaction and may therefore be important for TCR interaction. Residue substitutions at position 63 also affected T cell recognition, but in a more heterogeneous fashion. Peptide analogs or mutant viruses with a single amino acid substitution at position 63 (Asp to Asn or Tyr) reduced the responses of the T cell clones to variable extents, suggesting that Asp63 may form part of overlapping T cell determinants. However since the truncated peptide P53-62 was weakly recognized, then Asp63 may not form part of the TCR or Ia interaction site, but may affect recognition through a steric or charge effect when substituted by Asn or Tyr. Ag competition experiments with the two unrelated HA peptides, P48-68 and P118-138, recognized by distinct T cell clones in the context of the same restriction element (I-Ak), showed that the peptides did not compete for Ag presentation to the relevant T cell clones, whereas a structural analog of P48-68 was a potent inhibitor. This finding is discussed in relation to the nature of the binding site for peptide Ag on the class II molecule.
mesh_terms: D000818:Animals; D000938:Antigen-Presenting Cells / Q000276:immunology; D000940:Antigenic Variation; D001667:Binding, Competitive; D002999:Clone Cells / Q000145:classification / Q000276:immunology; D000939:Epitopes / Q000032:analysis* / Q000235:genetics; D006183:H-2 Antigens / Q000235:genetics; D019267:Hemagglutinin Glycoproteins, Influenza Virus; D006389:Hemagglutinins, Viral / Q000235:genetics / Q000276:immunology*; D000949:Histocompatibility Antigens Class II / Q000235:genetics*; D009980:Influenza A virus / Q000235:genetics / Q000276:immunology*; D051379:Mice; D008807:Mice, Inbred BALB C; D008808:Mice, Inbred CBA; D010455:Peptides / Q000138:chemical synthesis / Q000276:immunology*; D013601:T-Lymphocytes / Q000145:classification* / Q000276:immunology
chemical_list: D000939:Epitopes; D006183:H-2 Antigens; D019267:Hemagglutinin Glycoproteins, Influenza Virus; D006389:Hemagglutinins, Viral; D000949:Histocompatibility Antigens Class II; D010455:Peptides