Figure 1.

IL-27 and the IL-27R. The gp130 cytokine IL-27 is a heterodimeric cytokine comprising of a secreted receptor α-subunit and four-helix bundle protein (IL-27p28/EBI-3). The receptor complex for IL-27 contains gp130 and the IL-27R subunit-α, which is structurally similar to gp130. The intracellular domains of the receptor complex associate with the Janus kinases JAK1, JAK2 and Tyrosine kinase (TYK)2. IL-27-induced conformational changes of the receptor complex activate JAK1/TYK2 or JAK1/JAK2 and initiate a phosphorylation cascade that leads to the activation of signal transducer and activator of transcription (STAT)1 or STAT3, respectively. The IL-27R is predominantly expressed on T cells, Mϕ and DC where the Il-27R-mediated activation of STAT1/3 differentially affects the production of cell-type specific transcription factors.