IFN-γ-induced IL-27 and IL-27p28 expression are differentially regulated through JNK MAPK and PI3K pathways independent of Jak/STAT in human monocytic cells

IL-27, a member of the IL-12 cytokine family, is a key immunoregulatory cytokine produced predominantly by monocytic cells and mediates innate and adaptive immune responses. IL-27 has been shown to be produced by human monocytic cells primed with IFN-γ and in response to a second stimulus such as LPS. In this study, we show for the first time that IFN-γ alone without any second stimulus can induce IL-27p28 gene expression and IL-27 protein production by human monocytic cells. The signaling pathways that govern IL-27 production in general, and particularly following stimulation of monocytic cells with IFN-γ are not known. We investigated the signaling pathways governing the regulation of IL-27 protein and its subunit IL-27p28 following stimulation with IFN-γ in primary human monocytic cells. Our results suggest that IFN-γ-mediated IL-27 protein but not IL-27p28 gene expression is positively regulated by the C-Jun N-terminal kinases (JNK), mitogen-activated protein kinases (MAPKs) and the phosphoinositide 3-kinase (PI3K), independent of the Janus kinase (Jak)/signal transducers and activators of transcription (STAT) signaling in primary human monocytes.