title: Negative selection during the peripheral immune response to antigen.
abstract: Thymic selection depends on positive and negative selective mechanisms based on the avidity of T cell interaction with antigen-major histocompatibility complex complexes. However, peripheral mechanisms for the recruitment and clonal expansion of the responding T cell repertoire remain obscure. Here we provide evidence for an avidity-based model of peripheral T cell clonal expansion in response to antigenic challenge. We have used the encephalitogenic, H-2 A(u)-restricted, acetylated NH(2)-terminal nonameric peptide (Ac1-9) epitope from myelin basic protein as our model antigen. Peptide analogues were generated that varied in antigenic strength (as assessed by in vitro assay) based on differences in their binding affinity for A(u). In vivo, these analogues elicited distinct repertoires of T cells that displayed marked differences in antigen sensitivity. Immunization with the weakest (wild-type) antigen expanded the high affinity T cells required to induce encephalomyelitis. In contrast, immunization with strongly antigenic analogues led to the elimination of T cells bearing high affinity T cell receptors by apoptosis, thereby preventing disease development. Moreover, the T cell repertoire was consistently tuned to respond to the immunizing antigen with the same activation threshold. This tuning mechanism provides a peripheral control against the expansion of autoreactive T cells and has implications for immunotherapy and vaccine design.
authors.affiliation: Department of Pathology and Microbiology, School of Medical Sciences, University of Bristol, Bristol BS8 1TD, United Kingdom. steve.anderton@ed.ac.uk
authors.forename: S M
authors.initials: SM
authors.lastname: Anderton
authors.forename: C G
authors.initials: CG
authors.lastname: Radu
authors.forename: P A
authors.initials: PA
authors.lastname: Lowrey
authors.forename: E S
authors.initials: ES
authors.lastname: Ward
authors.forename: D C
authors.initials: DC
authors.lastname: Wraith
mesh_terms: D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D000818:Animals; D000936:Antigen-Antibody Complex / Q000276:immunology; D000941:Antigens / Q000008:administration & dosage* / Q000737:chemistry; D015551:Autoimmunity; D004681:Encephalomyelitis, Autoimmune, Experimental / Q000209:etiology / Q000276:immunology; D007114:Immunization; D016056:Immunodominant Epitopes / Q000008:administration & dosage / Q000737:chemistry; D066298:In Vitro Techniques; D051379:Mice; D008822:Mice, Transgenic; D004676:Myelin Basic Protein / Q000008:administration & dosage / Q000737:chemistry / Q000276:immunology; D013601:T-Lymphocytes / Q000276:immunology*
chemical_list: D000936:Antigen-Antibody Complex; D000941:Antigens; D016056:Immunodominant Epitopes; D004676:Myelin Basic Protein