title: Immunological self, nonself discrimination.
abstract: The ability of immunodominant peptides derived from several antigen systems to compete with each other for T cell activation was studied. Only peptides restricted by a given transplantation antigen are mutually competitive. There is a correlation between haplotype restriction, ability to bind to the appropriate transplantation antigen, and ability to inhibit activation of other T cells restricted by the same transplantation antigen. An exception was noted in that a peptide derived from an antigen, bacteriophage lambda cI repressor, binds to the I-Ed molecule in a specific way, yet is not I-Ed-restricted. Comparison of the sequence of the repressor peptide with that of other peptides able to bind to (and be restricted by) I-Ed and a polymorphic region of the I-Ed molecule itself revealed a significant degree of homology. Thus, peptides restricted by a given class II molecule appear to be homologous to a portion of the class II molecule itself. The repressor-derived peptide is identical at several polymorphic residues at this site, and this may account for the failure of I-Ed to act as a restriction element. Comparison of antigenic peptide sequences with transplantation antigen sequences suggests a model that provides a basis for explaining self, nonself discrimination as well as alloreactivity.
mesh_terms: D000818:Animals; D000941:Antigens / Q000276:immunology*; D001324:Autoantigens / Q000276:immunology; D004268:DNA-Binding Proteins; D000939:Epitopes; D000949:Histocompatibility Antigens Class II / Q000276:immunology*; D006825:Hybridomas; D007519:Isoantigens / Q000276:immunology; D008213:Lymphocyte Activation; D051379:Mice; D008836:Micrococcal Nuclease / Q000276:immunology; D010047:Ovalbumin / Q000276:immunology; D011485:Protein Binding; D011971:Receptors, Immunologic / Q000276:immunology*; D012097:Repressor Proteins / Q000276:immunology; D013601:T-Lymphocytes / Q000276:immunology*; D006377:T-Lymphocytes, Helper-Inducer / Q000276:immunology; D014764:Viral Proteins; D054334:Viral Regulatory and Accessory Proteins
chemical_list: D000941:Antigens; D001324:Autoantigens; D004268:DNA-Binding Proteins; D000939:Epitopes; D000949:Histocompatibility Antigens Class II; D007519:Isoantigens; D011971:Receptors, Immunologic; D012097:Repressor Proteins; D014764:Viral Proteins; D054334:Viral Regulatory and Accessory Proteins; C016649:phage repressor proteins; D010047:Ovalbumin; D008836:Micrococcal Nuclease