Listeria induces NKDC to produce IFN-gamma via IL-12, IL-18 and TLR9 ligation (44.24)

Abstract

Abstract Introduction: Natural killer dendritic cells (NKDC, NK1.1+CD11c+) are innate effector cells that secrete IFN-γ when stimulated. Initial control of Listeria monocytogenes (LM) infection depends on IFN-γ. The mechanism of IFN-γ secretion by NKDC in response to LM is unknown. Methods: NKDC and NK (NK1.1+CD3−) cells were isolated by fluorescence activated cell sorting from the spleens of C57BL/6 mice and cultured with LM strain 10403s at a multiplicity of infection of 1 for 3 days. IL-18 (20ng/ml), IL-12 blocking antibody (10μg/ml), or an inhibitory CpG (iCpG) sequence (50μg/ml) was added. Supernatant IFN-γ was analyzed by cytometric bead array. Results: LM infection or IL-18 alone did not induce significant IFN-γ production by NK cells or NKDC, however the combination of IL-18 and LM induced substantial amounts of IFN-γ from NKDC (19.3±2.7 ng/ml), and to a lesser extent, NK cells (2.0±0.6 ng/ml). Addition of anti-IL-12 antibody abrogated the IL-18/LM induced IFN-γ production of both NK cells and NKDC (<0.4 ng/ml). The addition of iCpG led to an 85% reduction of IL-18/LM induced IFN-γ production by NKDC and a 20% reduction by NK cells. Conclusion: IL-18, IL-12, and TLR9 ligation regulate NKDC IFN-γ production in response to LM. This work was supported by grant DK068346.