Human IL-27 Synthetic Peptide. IL-27 (Interleukin 27) is a cytokine belonging to the IL-12 family, and is a heterodimeric cytokine composed of EBI3 and p28 subunits. IL-27 is produced by activated dendritic cells and macrophages in response to Toll-like receptor ligands and pro-inflammatory cytokines. IL-27 promotes CD4+ T cell differentiation to the Th1 lineage by inducing expression of the transcription factor T-bet and up regulating IL-12R beta2, which in turn suppresses Th2 and Th17 differentiation and proliferation. IL-27 is a recently discovered member of the IL-6/IL-12 family of proinflammatory and immunoregulatory cytokines. IL-27 acts by binding to its receptor WSX-1 and gp130 which results in the activation of a Jak/STAT signaling