title: Subpopulations of the T4+ inducer T cell subset in man: evidence for an amplifier population preferentially expressing Ia antigen upon activation.
abstract: Prior studies demonstrated that Ia molecules were expressed on a fraction of human peripheral T4+ inducer cells upon stimulation by soluble antigen. In the present study, we utilized a fluorescence-activated cell sorter to separate antigen-activated T4+,Ia+ and T4+,Ia- populations and characterized their function. It was found that the T4+,Ia+ population contained the majority of proliferating T cells as assessed by tritiated thymidine incorporation. This proliferation largely appeared to be nonspecific. Despite macrophage repletion, elimination of the Ia+ subset of T cells with monoclonal anti-Ia antibody and complement treatment equally diminished subsequent proliferation to both the triggering antigen and an unrelated antigen. Moreover, the antigen-induced Ia+ subset of T cells alone produced a nonspecific helper factor, LMF. In contrast, the the T4+,Ia- population showed minimal proliferation to soluble antigen and did not generate LMF. Nevertheless, both T4+,Ia+ and T4+,Ia- inducer T cells were required to generate maximal immunoglobulin production by B cells in an antigen-driven system. We conclude that the human T4+ inducer T cell subset is comprised of at least 2 functionally distinct subpopulations, which are capable of acting in a synergistic fashion to provide help to B cells.
mesh_terms: D000906:Antibodies; D003165:Complement System Proteins; D000939:Epitopes; D000949:Histocompatibility Antigens Class II; D006801:Humans; D007074:Immunoglobulin G / Q000096:biosynthesis; D007376:Interleukin-2 / Q000096:biosynthesis; D008213:Lymphocyte Activation; D013601:T-Lymphocytes / Q000145:classification*; D013745:Tetanus Toxoid / Q000276:immunology
chemical_list: D000906:Antibodies; D000939:Epitopes; D000949:Histocompatibility Antigens Class II; D007074:Immunoglobulin G; D007376:Interleukin-2; D013745:Tetanus Toxoid; D003165:Complement System Proteins