title: Clonal analysis of functionally distinct human CD4+ T cell subsets.
abstract: A large number of CD4+ T cell clones, obtained from peripheral blood T lymphocytes by direct limiting dilution, allowed us to address the question whether functional heterogeneity exists within the human CD4+ T cell subset. Cytotoxic capacity of cloned T cells was analyzed with the use of anti-CD3 antibodies and target cells bearing FcR for murine IgG. 6 of 12 CD4+ clones obtained were able to lyse Daudi or P815 cells in the presence of anti-CD3 antibodies. The remaining six CD4+ T cell clones tested did not display anti-CD3-mediated cytotoxic activity and did not acquire this cytotoxic capacity during a culture period of 20 wk. In the absence of anti-CD3 mAb, no lytic activity against Daudi, P815, and K562 target cells was observed under normal culture conditions. Phenotypic analysis of these two distinct types of CD4+ T cells did not reveal differences with regard to reactivity with CDw29 (4B4) and CD45R (2H4) mAbs that have been described to recognize antigens associated with helper suppressor/inducer (respectively) CD4+ cells. The CD4+ clones without anti-CD3-mediated cytotoxic activities (Th2) consistently showed a high expression level of CD28 antigens, whereas the cytotoxic clones (Th1) expressed low amounts of CD28. Th1 CD4+ clones did produce IL-2, IFN-gamma, and TNF-alpha/beta, whereas the Th2 T cell clones produced minimal amounts of IL-2 and only low levels of INF-gamma and TNF-alpha/beta in response to anti-CD3 mAbs and PMA. Although not all CD4+ clones did release IL-4, there was no correlation with cytotoxic activity. Moreover, as compared with the Th1 CD4+ clones, Th2 CD4+ T cell clones proliferated moderately in response to immobilized anti-CD3 mAbs. However, proliferation reached the level of the cytotoxic clones when anti-CD28 mABs were present during culture. Both CD4+ subsets provided help for B cell differentiation upon stimulation with anti-CD3 mAbs. Our data suggest that the human CD4+ subset, in analogy to the murine system, comprises two functionally distinct T cell subpopulations, both of which are able to exert helper activity for polyclonal B cell differentiation, but which differ in cytotoxic capacity, lymphokine production, and requirements for proliferation. A function for these two types of T cells in the immune response is discussed.
mesh_terms: D000945:Antigens, Differentiation, T-Lymphocyte / Q000032:analysis; D018106:CD28 Antigens; D017252:CD3 Complex; D015496:CD4-Positive T-Lymphocytes / Q000145:classification* / Q000166:cytology / Q000502:physiology; D002999:Clone Cells; D003602:Cytotoxicity, Immunologic; D000949:Histocompatibility Antigens Class II / Q000032:analysis; D006801:Humans; D007111:Immunity, Cellular; D007376:Interleukin-2 / Q000494:pharmacology; D008213:Lymphocyte Activation; D008222:Lymphokines / Q000096:biosynthesis; D011948:Receptors, Antigen, T-Cell / Q000032:analysis
chemical_list: D000945:Antigens, Differentiation, T-Lymphocyte; D018106:CD28 Antigens; D017252:CD3 Complex; D000949:Histocompatibility Antigens Class II; D007376:Interleukin-2; D008222:Lymphokines; D011948:Receptors, Antigen, T-Cell