title: Immune suppression by recombinant interleukin (rIL)-12 involves interferon gamma induction of nitric oxide synthase 2 (iNOS) activity: inhibitors of NO generation reveal the extent of rIL-12 vaccine adjuvant effect.
abstract: Recombinant interleukin 12 (IL-12) can profoundly suppress cellular immune responses in mice. To define the underlying mechanism, recombinant murine (rm)IL-12 was given to C57BL/6 mice undergoing alloimmunization and found to transiently but profoundly suppress in vivo and in vitro allogeneic responses and in vitro splenocyte mitogenic responses. Use of neutralizing antibodies and genetically deficient mice showed that IFN-gamma (but not TNF-alpha) mediated rmIL-12-induced immune suppression. Splenocyte fractionation studies revealed that adherent cells from rmIL-12-treated mice suppressed the mitogenic response of normal nonadherent cells to concanavalin A and IL-2. Addition of an inhibitor of nitric oxide synthase (NOS) restored mitogenic responses, and inducible (i)NOS-/- mice were not immunosuppressed by rmIL-12. These results support the view that suppression of T cell responses is due to NO produced by macrophages responding to the high levels of IFN-gamma induced by rmIL-12. When a NOS inhibitor was given with rmIL-12 during vaccination of A/J mice with irradiated SCK tumor cells, immunosuppression was averted and the extent of rmIL-12's ability to enhance induction of protective antitumor immunity was revealed. This demonstrates that rmIL-12 is an effective vaccine adjuvant whose efficacy may be masked by its transient immunosuppressive effect.
authors.affiliation: Cell and Molecular Biology Graduate Group, Cancer Center, and Institute for Human Gene Therapy, School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA.
authors.forename: H K
authors.initials: HK
authors.lastname: Koblish
authors.forename: C A
authors.initials: CA
authors.lastname: Hunter
authors.forename: M
authors.initials: M
authors.lastname: Wysocka
authors.forename: G
authors.initials: G
authors.lastname: Trinchieri
authors.forename: W M
authors.initials: WM
authors.lastname: Lee
mesh_terms: D000276:Adjuvants, Immunologic / Q000008:administration & dosage / Q000494:pharmacology; D000818:Animals; D004790:Enzyme Induction / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D007108:Immune Tolerance / Q000187:drug effects*; D007166:Immunosuppressive Agents / Q000008:administration & dosage / Q000494:pharmacology; D007371:Interferon-gamma / Q000235:genetics / Q000378:metabolism*; D018664:Interleukin-12 / Q000008:administration & dosage / Q000494:pharmacology*; D008213:Lymphocyte Activation / Q000187:drug effects; D051379:Mice; D008805:Mice, Inbred A; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D009569:Nitric Oxide / Q000276:immunology; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors / Q000096:biosynthesis* / Q000235:genetics; D052247:Nitric Oxide Synthase Type II; D011994:Recombinant Proteins / Q000008:administration & dosage / Q000494:pharmacology; D013601:T-Lymphocytes / Q000187:drug effects / Q000276:immunology; D014612:Vaccines / Q000008:administration & dosage
chemical_list: D000276:Adjuvants, Immunologic; D004791:Enzyme Inhibitors; D007166:Immunosuppressive Agents; D011994:Recombinant Proteins; D014612:Vaccines; D018664:Interleukin-12; D009569:Nitric Oxide; D007371:Interferon-gamma; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II; C496317:Nos2 protein, mouse; D019331:NG-Nitroarginine Methyl Ester