Interleukin 12–dependent Interferon γ Production by CD8α+Lymphoid Dendritic Cells

Abstract

We investigated the role of antigen-presenting cells in early interferon (IFN)-γ production in normal and recombinase activating gene 2–deficient (Rag-2−/−) mice in response to Listeria monocytogenes (LM) infection and interleukin (IL)-12 administration. Levels of serum IFN-γ in Rag-2−/− mice were comparable to those of normal mice upon either LM infection or IL-12 injection. Depletion of natural killer (NK) cells by administration of anti-asialoGM1 antibodies had little effect on IFN-γ levels in the sera of Rag-2−/− mice after LM infection or IL-12 injection. Incubation of splenocytes from NK cell–depleted Rag-2−/− mice with LM resulted in the production of IFN-γ that was completely blocked by addition of anti–IL-12 antibodies. Both dendritic cells (DCs) and monocytes purified from splenocytes were capable of producing IFN-γ when cultured in the presence of IL-12. Intracellular immunofluorescence analysis confirmed the IFN-γ production from DCs. It was further shown that IFN-γ was produced predominantly by CD8α+ lymphoid DCs rather than CD8α− myeloid DCs. Collectively, our data indicated that DCs are potent in producing IFN-γ in response to IL-12 produced by bacterial infection and play an important role in innate immunity and subsequent T helper cell type 1 development in vivo.

In vivo role of IFN‐γ produced by antigen‐presenting cells in early host defense against intracellular pathogens

“…1). Depletion of NK cells by administration of antiasialoGM1 antibody ( § AGM1) had little effect on IFN-+ production as reported previously [14]. However, IFN-+ production was negligible when DC and macrophages were further removed from the NK-depleted Rag-2 -/-splenocytes by anti-CD11c-and anti-MHC class IIconjugated magnetic beads.…”

“…Although DC and macrophages are normally present in + c -/-(y) -Rag-2 -/-mice [14,30,33], the amount of IFN-+ produced by + c -/-(y) -Rag-2 -/-splenocytes in response to L. monocytogenes was about 1/10,000 as compared to that from NK celldepleted Rag-2 -/-splenocytes ( Fig. 1 and [33]).…”

“…IFN-+ gene knockout (IFN-+ -/-) mice, IFN-+ receptor gene knockout (IFN-+ R -/-) mice, as well as other IFN-+ -related gene knockout mice are extremely susceptible to intracellular pathogens compared to SCID or wild-type (WT) mice [5][6][7][8][9][10][11][12][13]. Whereas NK cells among lymphoid cells had been believed to be a major source of IFN-+ during early phase of infection, we and others have shown that antigen-presenting cells (APC) such as dendritic cells (DC) and macrophages produce large amounts of IFN-+ in response to interleukin (IL)-12 that is produced by APC upon microbial infection [14][15][16][17][18][19][20][21][22][23][24][25][26][27]. In fact, amounts of IFN-+ produced by DC and macrophages are substantially larger than those produced by NK cells [14][15][16].…”

“…Whereas NK cells among lymphoid cells had been believed to be a major source of IFN-+ during early phase of infection, we and others have shown that antigen-presenting cells (APC) such as dendritic cells (DC) and macrophages produce large amounts of IFN-+ in response to interleukin (IL)-12 that is produced by APC upon microbial infection [14][15][16][17][18][19][20][21][22][23][24][25][26][27]. In fact, amounts of IFN-+ produced by DC and macrophages are substantially larger than those produced by NK cells [14][15][16]. Other cytokines such as IL-18, IL-2, and IL-4 synergize the effect of IL-12 on the production of IFN-+ from mature DC [15,16].…”

“…DC and macrophages develop in + c -/-(y) -Rag-2 -/-mice but the lack of IL-15 receptor signals involving + c leads to the impaired production of IL-12 and IFN-+ from DC and macrophages in + c -/-(y) -Rag-2 -/-mice [14,30,33]. In this study, we employed + c -/-(y) -Rag-2 -/-mice to examine the in vivo role of IFN-+ from APC against the intracellular microorganisms L. monocytogenes and T. gondii.…”