title: Recognition requirements for the activation, differentiation and function of T-helper cells specific for class I MHC alloantigens.
abstract: The present review has focused on the specificity of the T-helper cell populations initiating MHC class I alloreactions. In contrast to conventional immune responses against soluble antigens, responses against membrane-bound class I alloantigens are initiated by two distinct antigen-specific T-helper cell populations that can be distinguished by their Lyt phenotype, MHC restriction specificity, antigen specificity, and requirement for thymically determined self-recognition. Alloresponses were shown to be a composite consisting of two distinct components: one mediated by L3T4+ Th cells and very similar to conventional self + X responses; and one mediated by Lyt2+ Th cells and unique to alloresponses against MHC class I antigens. As would befit an unusual Th cell population, the recognition/response spectrum of Lyt2+ Th cells was highly unusual and was found to be the basis for much of the uniqueness we attribute to immune alloreactions, including rapid rejection of tissue allografts in vivo.
mesh_terms: D000818:Animals; D003602:Cytotoxicity, Immunologic; D007376:Interleukin-2 / Q000276:immunology; D007519:Isoantigens / Q000235:genetics*; D008213:Lymphocyte Activation; D008285:Major Histocompatibility Complex; D051379:Mice; D008815:Mice, Inbred Strains; D016038:Skin Transplantation; D006377:T-Lymphocytes, Helper-Inducer / Q000276:immunology*
chemical_list: D007376:Interleukin-2; D007519:Isoantigens