STAT3 Inhibits Autocrine Interferon Signaling in Type I Conventional Dendritic Cells

Type I conventional dendritic cells (cDC1s) are an essential antigen-presenting population, required for generating adaptive immunity against intracellular pathogens and tumors. While the transcriptional control of cDC1 development is well understood, the mechanisms by which extracellular stimuli affect cDC1 function remain unclear. Recently, we demonstrated that the cytokine IL-10 inhibits cDC1 maturation induced upon polyinosinic-polycytidylic acid (poly I:C) exposure via a STAT3-dependent mechanism. Furthermore, utilizing a tumor vaccine strategy, we found STAT3 restrains cDC1-mediated anti-tumor immunity. To understand the pathways by which IL-10 and STAT3 regulate cDC1s, we evaluated transcriptional responses by RNA-sequencing. Bioinformatic analyses indicated that many inflammatory pathways were enriched in cDC1s following poly I:C treatment, while interferon (IFN) signaling was uniquely inhibited by STAT3 upon concomitant exposure to IL-10. We found that poly I:C stimulated production of IFN-b and IFN-g from cDC1s. Concurrent exposure to IL-10 suppressed IFN-b and IFN-g secretion as well as accrual of phosphorylated STAT1 and expression of the IFN-response gene Cxcl10 in cDC1s. By contrast, Stat3-deficient cDC1s were refractory to IL-10, indicating STAT3 controls poly I:C-mediated IFN production and IFN transcriptional responses in cDC1s. Moreover, we found that maturation of cDC1s in response to poly I:C is dependent on the type I IFN receptor. Taken together, our data indicate STAT3 is essential for restraining autocrine type I IFN signaling in cDC1s elicited by poly I:C stimulation. Overall design: STAT3fl/fl CD11c-Cre- and STAT3fl/fl CD11c-Cre+ in-vitro derived cDC1s were treated with PBS, IL-10 (10 ng/mL), poly I:C (20 ug/mL), or IL-10 + poly I:C for 6 hours. n = 3 per genotype and treatment condition