IFN-beta modulates the response to TLR stimulation in human DC: involvement of IFN regulatory factor-1 (IRF-1) in IL-27 gene expression.

Type I IFN are cytokines which play a central role in host resistance to viral or microbial infections and are important components linking innate and adaptive immunity. We and others have previously demonstrated that the production of IFN-beta by DC following bacterial infections or TLR triggering influences, in an autocrine manner, their maturation. In this study, we investigated whether IFN-beta release modulates the phenotype of the immature DC and their response to a subsequent TLR stimulation. The induction of CD86, HLA-DR, CD38 and B7H1 and the absence of CCR7 and CD83 expression upon IFN-beta treatment suggest that IFN-beta-primed DC remain at the site of infection acquiring an activated phenotype. These results prompted us to investigate the response of IFN-beta-primed DC to TLR stimulation. While IFN-beta pretreatment increases slightly the expression of maturation markers in TLR2- or TLR4-stimulated DC, it is able to modulate selectively the secretion of inflammatory and immuno-regulating cytokines. Interestingly, IL-27p28 subunit was induced by IFN-beta alone or during LPS-induced maturation of DC in a type I IFN-dependent manner through IFN regulatory factor-1 (IRF-1) activation. Taken together, our results shed light on the capacity of IFN-beta to finely tune DC response to invading pathogens.