title: T-helper cells from naive to committed.
abstract: T-helper cells play a central role in the onset and regulation of the antigen-specific immune response. In swine, two subpopulations of CD4 positive T-helper cells could be defined in extra-thymic compartments. Both differ in the surface antigen expression of distinct antigens. Besides the CD4(+)CD8(-) T-helper cell subpopulation representing the phenotype of T-helper cells known from other species, in swine CD4(+) T-helper cells exist showing expression of CD8alpha and MHCII molecules.In primary in vitro immune reactions after simulation with SEB the main response is distributed to the CD4(+)CD8(-) T-cell subpopulation, which contains the majority of naive T-helper cells. During the immune response CD8alpha as well as MHCII molecules are expressed on the surface of activated T-helper cells. This in vitro maturation is combined with a down-regulation of CD45RC. Thus, activated T-helper cells represent a cell phenotype with high similarity to the second porcine T-helper cell subpopulation. This CD4(+)CD8alpha(+) subpopulation contains in its majority MHCII(+) and CD45RC(-) cells. In a secondary in vitro immune response against classical swine fever virus only the CD4(+)CD8(+) T-helper subpopulation is able to respond. Therefore, T-helper memory cells can be distributed to this T-lymphocyte subpopulation. In summary, naive CD4(+)CD8(-)MHCII(-) porcine T-helper cells show an extra-thymic maturation to committed CD4(+)CD8alpha(+)MHCII(+) T-helper cells.
authors.affiliation: Institute for Immunology, Federal Research Centre for Virus Diseases of Animals, P.O. Box 1149, Paul-Ehrlich-Strasse 28, 72076 Tübingen, Germany. armin.saalmueller@tue.bfav.de
authors.forename: Armin
authors.initials: A
authors.lastname: Saalmüller
authors.forename: Tobias
authors.initials: T
authors.lastname: Werner
authors.forename: Vicky
authors.initials: V
authors.lastname: Fachinger
mesh_terms: D000818:Animals; D015704:CD4 Antigens / Q000032:analysis; D016827:CD8 Antigens / Q000032:analysis; D007156:Immunologic Memory; D016130:Immunophenotyping; D008213:Lymphocyte Activation; D013552:Swine / Q000276:immunology*; D006377:T-Lymphocytes, Helper-Inducer / Q000276:immunology*
chemical_list: D015704:CD4 Antigens; D016827:CD8 Antigens