Fas ligand induces cell-autonomous IL-23 production in dendritic cells, a mechanism for Fas ligand-induced IL-17 production

Fas ligand (FasL) has the potential to induce inflammation accompanied by massive neutrophil infiltration. We previously reported that FasL rapidly induces the production of various inflammatory cytokines including IL-1 beta and IL-17. In this study, we investigated the mechanism of the FasL-induced IL-17 production. We found that the culture supernatant of mouse resident peritoneal exudate cells (PEC) cocultured with FasL-expressing tumor (FFL) cells induced IL-17 production in freshly isolated resident PEC. Anti-IL-1 beta Ab strongly inhibited the IL-17-inducing activity. However, rIL-1 beta by itself induced only weak IL-17 production. Intriguingly, anti-IL-12 Ab but not an IL-15-neutralizing agent, IL15R-Fc, strongly inhibited the FaSL-induced IL-17-inducing activity. IL-23, which shares the p40 subunit with IL-12, but not IL-12 itself, induced IL-17 production synergistically with IL-1 beta in resident PEC. FasL induced the production of IL-23 in PEC in vivo and in vitro, and IL-17 production following the i.p. injection of FFL cells was severely impaired in p40(-/-) mice, indicating that IL-23 plays an important role ill the FasL-induced IL-17 production. FFL, also induced the production of IL-23 in bone marrow- or PEC-derived dendritic cells (DCs). Finally, FasL induced only weak p40 production in a mixture of p40(-/-) and Fas(-/-) DC, indicating that FasL induces IL-23 production in DC mainly in a cell-autonomous manner.