title: Functional characterization of porcine CD4+CD8+ extrathymic T lymphocytes.
abstract: The porcine immune system is unique in that the expression of CD4 and CD8 antigens defines four subpopulations of resting, extrathymic (CD1-) T lymphocytes. In addition to CD4-CD8+ and CD4+CD8- T lymphocytes, CD4-CD8- and CD4+CD8+ lymphocyte subpopulations are prominent in blood as well as in lymphoid tissues. In the present study, a functional comparison was made between CD4+CD8- and CD4+CD8+ T lymphocyte subpopulations. In a primary in vitro immune response against alloantigenic stimulator cells, both subpopulations proliferated without significant differences in their reactivity. Different results were obtained when analyzing the antigen-specific functions of the two CD4+ subpopulations in a secondary response against recall viral antigen; these experiments were performed with T lymphocytes from pseudorabies virus-immunized pigs. The proliferative response against viral antigens could be assigned to the CD4+CD8+ subpopulation, whereas the CD4+CD8- subpopulation remained nonreactive. Further analyses of the virus-specific in vitro immune response revealed a major histocompatibility complex (MHC) class II restricted helper T lymphocyte reaction involving CD4 but not CD8 molecules as restriction elements. Taken together, these results demonstrate that only the extrathymic CD4+CD8+ T lymphocyte subpopulation of swine contains MHC class II-restricted antigen-specific memory T helper cells.
authors.affiliation: Institut für Viruskrankheiten und Immunprophylaxe, Mittelhäusern, Switzerland.
authors.forename: A
authors.initials: A
authors.lastname: Summerfield
authors.forename: H J
authors.initials: HJ
authors.lastname: Rziha
authors.forename: A
authors.initials: A
authors.lastname: Saalmüller
mesh_terms: D000818:Animals; D000956:Antigens, Viral / Q000276:immunology; D015704:CD4 Antigens; D016827:CD8 Antigens; D002455:Cell Division; D002478:Cells, Cultured; D005434:Flow Cytometry; D000949:Histocompatibility Antigens Class II / Q000276:immunology; D007114:Immunization; D007156:Immunologic Memory; D016130:Immunophenotyping; D008213:Lymphocyte Activation; D011557:Pseudorabies / Q000276:immunology; D013552:Swine; D013556:Swine, Miniature / Q000097:blood / Q000276:immunology*; D016176:T-Lymphocyte Subsets / Q000145:classification / Q000276:immunology*; D006377:T-Lymphocytes, Helper-Inducer / Q000276:immunology
chemical_list: D000956:Antigens, Viral; D015704:CD4 Antigens; D016827:CD8 Antigens; D000949:Histocompatibility Antigens Class II