title: Flexibility in MHC and TCR recognition: degenerate specificity at the T cell level in the recognition of promiscuous Th epitopes exhibiting no primary sequence homology.
abstract: Recognition of peptide Ags by T cells through the TCR can be highly specific. In this report we show the degeneracy of Ag recognition at both MHC and TCR levels. We present evidence that unrelated promiscuous Th cell epitopes from various protein sources exhibit sufficient structural homology, despite minimal structural identity, to elicit cross-reactive proliferative responses at the bulk T cell level. This epitopic mimicry was also observed when peptide (CS.T3(378-395) and TT(830-844))-specific CD4+ T cell lines and T cell hybridoma clones were used in proliferation and Ag presentation assays. A scrambled CS.T3(378-395) peptide did not show any proliferation, indicating that the specificity of the cross-reactive responses may be linked with the primary structure of the peptides. Blocking of CS.T3(378-395)-specific CD4+ T cell proliferation by anti-MHC class II mAb showed that recognition of promiscuous T cell epitopes is largely in association with MHC class II molecules. These findings suggest that promiscuous Th epitopes may be useful in designing peptide-based vaccine constructs. At the same time these results show that at the T cell level there may be a great deal of immunological cross-reactivity between heterologous pathogens, and because of this the host's response to a pathogen may be modified by its previous experience with other unrelated pathogens.
authors.affiliation: Malaria Research Group, International Center for Genetic Engineering and Biotechnology, Aruna Asaf Ali Marg, New Delhi 110067, India.
authors.forename: S K
authors.initials: SK
authors.lastname: Joshi
authors.forename: P R
authors.initials: PR
authors.lastname: Suresh
authors.forename: V S
authors.initials: VS
authors.lastname: Chauhan
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D000911:Antibodies, Monoclonal / Q000494:pharmacology; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology / Q000378:metabolism; D002460:Cell Line; D002999:Clone Cells; D018984:Epitopes, T-Lymphocyte / Q000378:metabolism*; D005260:Female; D019674:Genes, T-Cell Receptor beta; D000949:Histocompatibility Antigens Class II / Q000276:immunology / Q000378:metabolism*; D006825:Hybridomas / Q000378:metabolism; D008213:Lymphocyte Activation / Q000276:immunology; D051379:Mice; D008807:Mice, Inbred BALB C; D008809:Mice, Inbred C3H; D008810:Mice, Inbred C57BL; D008811:Mice, Inbred DBA; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000037:antagonists & inhibitors / Q000276:immunology / Q000378:metabolism; D010963:Plasmodium falciparum / Q000276:immunology; D011485:Protein Binding / Q000276:immunology; D015800:Protozoan Proteins / Q000276:immunology / Q000378:metabolism; D011948:Receptors, Antigen, T-Cell / Q000235:genetics / Q000378:metabolism*; D016693:Receptors, Antigen, T-Cell, alpha-beta / Q000096:biosynthesis / Q000235:genetics; D017386:Sequence Homology, Amino Acid; D013045:Species Specificity; D006377:T-Lymphocytes, Helper-Inducer / Q000276:immunology* / Q000378:metabolism*; D014407:Tumor Cells, Cultured
chemical_list: D000911:Antibodies, Monoclonal; D018984:Epitopes, T-Lymphocyte; D000949:Histocompatibility Antigens Class II; D010446:Peptide Fragments; D015800:Protozoan Proteins; D011948:Receptors, Antigen, T-Cell; D016693:Receptors, Antigen, T-Cell, alpha-beta