title: Antigen-driven but not lipopolysaccharide-driven IL-12 production in macrophages requires triggering of CD40.
abstract: We demonstrated that two distinct pathways exist for the induction of IL-12 in APC. The first pathway for IL-12 production occurred during responses to T cell-dependent Ags such as OVA and required triggering of CD40 molecules on the APC. IL-12 production in this T cell-dependent system increased in direct proportion to Ag concentration and required TCR ligation but not CD28 costimulation. The second pathway occurred when bacterial products such as LPS or heat-killed Listeria monocytogenes were used to activate macrophages to produce IL-12 in the complete absence of T cells. In this second pathway, IL-12 production was completely independent of CD40 triggering. In both pathways, the presence of IFN-gamma was not required for induction of IL-12 synthesis when splenic adherent cells (SAC) from normal mice were used. However, addition of IFN-gamma to cultures of Th2 T cells and SAC increased IL-12 production two- to fivefold, and addition of rTNF-alpha with IFN-gamma further enhanced IL-12 production. The addition of TNF-alpha in the absence of IFN-gamma, however, had no effect on IL-12 production in the T cell-dependent pathway. Similarly, addition of TNF-alpha in the presence or the absence of IFN-gamma to cultures of LPS or heat-killed Listeria and SAC did not increase IL-12 production, but addition of IFN-gamma alone greatly enhanced IL-12 production, consistent with the idea that bacterial stimuli induce significant quantities of endogenous TNF-alpha production. These results indicate that the requirements for the induction of IL-12 production in T cell-dependent and T cell-independent responses differs mainly with regard to CD40 triggering. Furthermore, these results suggest that IL-12 production can be induced by bacterial products in patients with hyper-IgM syndrome who lack CD40 ligand expression and in those treated with soluble gp39 to interrupt CD40-CD40 ligand interactions.
authors.affiliation: Division of Immunology and Transplantation Biology, Department of Pediatrics, Stanford University, CA 94305, USA.
authors.forename: R H
authors.initials: RH
authors.lastname: DeKruyff
authors.forename: R S
authors.initials: RS
authors.lastname: Gieni
authors.forename: D T
authors.initials: DT
authors.lastname: Umetsu
mesh_terms: D000276:Adjuvants, Immunologic / Q000494:pharmacology; D000818:Animals; D000941:Antigens / Q000276:immunology / Q000494:pharmacology; D019013:CD40 Antigens / Q000187:drug effects* / Q000378:metabolism*; D006433:Hemocyanins / Q000494:pharmacology; D007371:Interferon-gamma / Q000494:pharmacology; D016753:Interleukin-10 / Q000096:biosynthesis / Q000494:pharmacology; D018664:Interleukin-12 / Q000037:antagonists & inhibitors / Q000096:biosynthesis*; D008070:Lipopolysaccharides / Q000494:pharmacology*; D008264:Macrophages / Q000187:drug effects* / Q000378:metabolism*; D051379:Mice; D008807:Mice, Inbred BALB C; D008811:Mice, Inbred DBA; D010047:Ovalbumin / Q000276:immunology* / Q000494:pharmacology*; D018418:Th2 Cells / Q000378:metabolism; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology
chemical_list: D000276:Adjuvants, Immunologic; D000941:Antigens; D019013:CD40 Antigens; D008070:Lipopolysaccharides; D014409:Tumor Necrosis Factor-alpha; D016753:Interleukin-10; D018664:Interleukin-12; D007371:Interferon-gamma; D010047:Ovalbumin; D006433:Hemocyanins; C032808:keyhole-limpet hemocyanin