title: A two-step, two-signal model for the primary activation of precursor helper T cells.
abstract: I present here a new model for the primary activation of precursor helper T cells. Observations demonstrate that the immune system learns not to respond to extrathymic, organ-specific self-antigens because of their early appearance in development. The immune system thus discriminates between peripheral self-antigens and foreign antigens and, when mature, usually makes an immune response against only the latter. Contemporary models for the activation and inactivation of T helper (Th) function do not account for such discrimination. The model proposed here is consistent with contemporary findings and incorporates a mechanism of peripheral self-nonself discrimination.
authors.affiliation: Department of Microbiology and Immunology, University of Saskatchewan, 107 Wiggins Road, Saskatoon, Saskatchewan, S7N 5E5 Canada. bretschr@duke.usak.ca
authors.forename: P A
authors.initials: PA
authors.lastname: Bretscher
mesh_terms: D017951:Antigen Presentation; D000939:Epitopes; D000949:Histocompatibility Antigens Class II; D007108:Immune Tolerance; D008213:Lymphocyte Activation; D018448:Models, Immunological; D015398:Signal Transduction; D006377:T-Lymphocytes, Helper-Inducer / Q000276:immunology*; D018417:Th1 Cells / Q000276:immunology; D018418:Th2 Cells / Q000276:immunology
chemical_list: D000939:Epitopes; D000949:Histocompatibility Antigens Class II