Differential production of type I IFN determines the reciprocal levels of IL-10 and proinflammatory cytokines produced by C57BL/6 and BALB/c macrophages

Pattern recognition receptors detect microbial products and induce cytokines, which shape the immunological response. IL-12, TNF-alpha, and IL-1 beta are proinflammatory cytokines, which are essential for resistance against infection, but when produced at high levels they may contribute to immunopathology. In contrast, IL-10 is an immunosuppressive cytokine, which dampens proinflammatory responses, but it can also lead to defective pathogen clearance. The regulation of these cytokines is therefore central to the generation of an effective but balanced immune response. In this study, we show that macrophages derived from C57BL/6 mice produce low levels of IL-12, TNF-alpha, and IL-1 beta, but high levels of IL-10, in response to TLR4 and TLR2 ligands LPS and Pam3CSK4, as well as Burkholderia pseudomallei, a Gram-negative bacterium that activates TLR2/4. In contrast, macrophages derived from BALB/c mice show a reciprocal pattern of cytokine production. Differential production of IL-10 in B. pseudomallei and LPS-stimulated C57BL/6 and BALB/c macrophages was due to a type I IFN and ERK1/2-dependent, but IL-27-independent, mechanism. Enhanced type I IFN expression in LPS-stimulated C57BL/6 macrophages was accompanied by increased STAT1 and IFN regulatory factor 3 activation. Furthermore, type I IFN contributed to differential IL-1 beta and IL-12 production in B. pseudomallei and LPS-stimulated C57BL/6 and BALB/c macrophages via both IL-10-dependent and -independent mechanisms. These findings highlight key pathways responsible for the regulation of pro- and anti-inflammatory cytokines in macrophages and reveal how they may differ according to the genetic background of the host. his work was supported by The Francis Crick Institute, which receives its core funding from Cancer Research UK (FC001126), the U.K. Medical Research Council (FC001126), and the Wellcome Trust (FC001126) since April 1, 2015 and before that by U.K. Medical Research Council Grant MRC U117565642 and also by European Research Council Grant 294682-TB-PATH (Crick 10127). A.H. was additionally funded by a U.K. Medical Research Council Centenary Award. M.S. was funded by Fundação para a Ciência e Tecnologia, Portugal Grant FCT-ANR/BIM-MEC/ 0007/2013. M.S. is an associate Fundação para a Ciência e Tecnologia, Portugal investigator.