title: Two signal model of self/not-self immune discrimination: an update.
abstract: From a consideration of the evolution of the first immune systems in simple organisms, it is proposed that mechanisms for self/not-self discrimination evolved at an early stage of evolution in prototypic B cells, prior to separation of the B cell and T cell lineages. After passing an MHC protein-limited self/not-self discrimination gate, T cells depend for fine self/not-self discrimination either on B cells (extracellular discrimination) or on cells harbouring pathogens (intracellular discrimination). Full activation of B cells needs interaction with T cells, but this evolved late and is not part of the self/not-self decision.
authors.affiliation: Department of Biochemistry, Queen's University, Kingston, Ontario, Canada.
authors.forename: D R
authors.initials: DR
authors.lastname: Forsdyke
mesh_terms: D000818:Animals; D001402:B-Lymphocytes / Q000276:immunology*; D005075:Biological Evolution; D006680:HLA Antigens / Q000276:immunology; D007111:Immunity, Cellular / Q000502:physiology*; D008213:Lymphocyte Activation / Q000276:immunology; D008954:Models, Biological; D016176:T-Lymphocyte Subsets / Q000276:immunology
chemical_list: D006680:HLA Antigens