title: Synergistic effects of IL-7 and IL-12 on human T cell activation.
abstract: We have previously demonstrated that human rIL-12 alone can augment the development of cytotoxic activity in stimulated CD8+ T cells. The present study was undertaken to examine the interactions of rIL-7 and rIL-12 on human peripheral blood T cell activation and CTL differentiation. Purified T lymphocytes were pulsed overnight with immobilized alpha-CD3 and then cultured for 3 additional days with IL-7 and/or IL-12. The combination of IL-7 and IL-12 synergistically enhanced the proliferation of either fresh CD3+ T cells or an IL-2-dependent CD4+ T cell line, Kit-225-K6. This synergy was seen on both subsets of T cells; however, CD8+ T cells were usually more responsive to IL-7 and IL-12 at lower concentrations than were CD4+ T cells. Furthermore, these cytokines additively/synergistically augmented the cytotoxic activity of CD8+ T cells. Abs to IL-2 and IL-2R alpha blocked the synergistic effect on proliferation of CD4+ T cells, but had a minimal effect on the synergistic response of the proliferative and cytotoxic activity of CD8+ T cells. Examination of the effects of IL-7 and IL-12 on the expression of IL-12 receptor on T cells revealed an increase in the subunit of IL-12R by IL-7 as determined by flow cytometric analysis. We analyzed the effects on IFN-gamma production by CD8+ T cells and found that IL-7 alone did not induce detectable levels of IFN-gamma production but together with IL-12 it synergistically enhanced the production of IFN-gamma. We also found that IFN-gamma was probably not required for enhanced CTL activity of CD8+ T cells, because Ab to human IFN-gamma did not block additive/synergistic effects of either cytokine. The synergistic stimulatory activity of IL-7 and IL-12 may be of significance in vivo and may provide an alternative mechanism of stimulating T cells for use in immunotherapy.
authors.affiliation: Laboratory of Cellular Immunology, Food and Drug Administration, Rockville, MD 20852, USA.
authors.forename: P T
authors.initials: PT
authors.lastname: Mehrotra
authors.forename: A J
authors.initials: AJ
authors.lastname: Grant
authors.forename: J P
authors.initials: JP
authors.lastname: Siegel
mesh_terms: D000911:Antibodies, Monoclonal / Q000276:immunology; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology; D018414:CD8-Positive T-Lymphocytes / Q000187:drug effects / Q000276:immunology; D002478:Cells, Cultured; D003601:Cytotoxicity Tests, Immunologic; D003602:Cytotoxicity, Immunologic / Q000187:drug effects; D004357:Drug Synergism; D004797:Enzyme-Linked Immunosorbent Assay; D005434:Flow Cytometry; D006801:Humans; D007371:Interferon-gamma / Q000096:biosynthesis; D018664:Interleukin-12 / Q000276:immunology / Q000494:pharmacology*; D007376:Interleukin-2 / Q000502:physiology; D015851:Interleukin-7 / Q000276:immunology / Q000494:pharmacology*; D008213:Lymphocyte Activation / Q000187:drug effects* / Q000276:immunology; D018123:Receptors, Interleukin / Q000096:biosynthesis; D053707:Receptors, Interleukin-12; D011994:Recombinant Proteins / Q000494:pharmacology; D013601:T-Lymphocytes / Q000187:drug effects* / Q000276:immunology; D015854:Up-Regulation / Q000502:physiology
chemical_list: D000911:Antibodies, Monoclonal; D007376:Interleukin-2; D015851:Interleukin-7; D018123:Receptors, Interleukin; D053707:Receptors, Interleukin-12; D011994:Recombinant Proteins; D018664:Interleukin-12; D007371:Interferon-gamma