Engagement of CD40 on antigen presenting cells (APC) is central to the initiation of cell-mediated immune response. Here, we investigated the ability of CD40 ligation on APC to induce NK cell-mediated cytotoxicity in the human system and the mechanism(s) underlying this process. We showed that APC (consisting in adherent peripheral blood mononuclear cells) (PBMC), pre-stimulated with anti-CD40 monoclonal antibodies and co-cultured with autologous non-adherent PBMC for 5-9 days, induced CD3-/CD56+ NK cell-mediated cytotoxicity as well as CD3+/CD56+ T cell-mediated unrestricted cytotoxic activity. The generation of NK cell-mediated cytotoxicity was independent on cell-to-cell contact between CD40-triggered APC and NK cells. Moreover, we found that IL-12 did not play a role in NK cells induction by anti-CD40 priming, while IL-2 and IL-15 did play a role. Our results provide an insight into the mechanism by which NK cells are activated in peripheral blood and useful informations for therapeutic application of anti-CD40 antibodies.
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