Interleukin-27 protein is related to IL-12A & is one of the subunits of a heterodimeric cytokine complex. IL-27 interacts with EBV induced gene 3 also called EBI3，and forms a complex that drives rapid expansion of CD4 （+） T cells.
IL-27 complex is synergizes with IL-12 in order to trigger the cytokine production of IFN-Gamma of CD4 （+） T cells. The biological effect of IL-27 is mediated by class-I cytokine receptor （WSX1/TCRR）.
The pro-inflammatory activity of IL-27 is mediated through the growing expression of key molecules involved in the MHC class-I & MHC class-II pathways. Both MHC class-I and MHC-class-II expression are increased in endothelial cells after Interleukin-27 stimulation which suggests that it may play an important role in conferring the immune function on vascular endothelium IL-27p28 subunit can be induced by IFN-beta and during LPS-induced maturation of dendritic cells in type-I IFN-dependent manner through IFN regulatory factor-1 activation. Interleukin-27 regulates Interleukin-12 responsiveness of CD4+ T cells through Stat1-dependent and -independent mechanisms. IL-17 & IL-23 play an important IL-17 role in inflammation. Interleukin-27 possesses potent anti-angiogenic activity that plays an important role in its antitumor and antimetastatic activities.
EBV induced gene 3 plays a role，independently from IL-27，in regulating anti-viral or anti-tumoral immune responses. Interleukin-27 is a potent inhibitor of HIV-1 replication in macrophages，CD4+ T cells，peripheral blood mononuclear cells.
Interleukin-27 triggers STAT activation and gene transcription.
