title: A previously unrecognized large fraction of cytotoxic lymphocyte precursors is present in CD4+ human peripheral blood T cells.
abstract: We describe a limiting dilution (LD) culture system in which cell sorter-purified CD4+ (and CD8+) peripheral blood T cells are cocultured with irradiated, anti-CD3 mab-producing OKT3 hybridoma cells. Under these conditions, one out of 2-3 CD4+ (and CD8+) T cells is induced to clonal proliferation. In striking contrast to previously described LD culture systems, every growing CD4+ cell clone displayed cytotoxic activity when tested in a lectin-facilitated 51Cr release assay against P815 target cells. This contrasts with the development of cytotoxic CD4+ T cells in alloantigen-stimulated LD cultures, where only one out of 15-20 proliferating CD4+ cells killed P815 in the presence of PHA, and one out of 300-500 proliferating CD4+ cells displayed alloantigen-specific cytotoxic activity. Furthermore, we have established antigen-specific proliferating CD4+ T cell clones which do not exert antigen-specific cytotoxicity but can be cytotoxic when crosslinked to target cells via lectin or monoclonal antibody (anti-CD3, anti-TCR). Our results show that a previously unrecognized large fraction (at least 30-50%) of all peripheral blood CD4+ T cells can give rise to cytotoxic effector cells. The mode of CD4+ T cell activation (OKT3 hybridoma versus alloantigen) thus determines whether the intrinsic cytotoxic capacity of CD4+ T cells is functionally activated or not.
authors.affiliation: Department of Medical Microbiology and Immunology, University of Ulm, Federal Republic of Germany.
authors.forename: D
authors.initials: D
authors.lastname: Kabelitz
authors.forename: C
authors.initials: C
authors.lastname: Brucker
authors.forename: H
authors.initials: H
authors.lastname: Wagner
authors.forename: B
authors.initials: B
authors.lastname: Fleischer
mesh_terms: D000945:Antigens, Differentiation, T-Lymphocyte / Q000276:immunology; D017252:CD3 Complex; D015496:CD4-Positive T-Lymphocytes / Q000166:cytology / Q000276:immunology*; D016827:CD8 Antigens; D002454:Cell Differentiation; D002469:Cell Separation; D002478:Cells, Cultured; D003602:Cytotoxicity, Immunologic; D005434:Flow Cytometry; D006801:Humans; D006825:Hybridomas; D007111:Immunity, Cellular; D007376:Interleukin-2 / Q000494:pharmacology; D011948:Receptors, Antigen, T-Cell / Q000276:immunology; D013602:T-Lymphocytes, Cytotoxic / Q000166:cytology* / Q000276:immunology
chemical_list: D000945:Antigens, Differentiation, T-Lymphocyte; D017252:CD3 Complex; D016827:CD8 Antigens; D007376:Interleukin-2; D011948:Receptors, Antigen, T-Cell