The receptor chains are also utilized by multiple cytokines (Fig. 1)1,2. IL-12 signals via IL12R?1 and IL12R?248,71,72, while IL-23 signals through IL12R?1 and IL23R69,73. In contrast, IL-27 utilizes gp130 and WSX-174, while IL-35 signals via gp130 and IL12R?228. IL-35 is unusual in that it can also signals via two additional receptor chain compositions; gp130-gp130 and IL12R?2-lL12R?2 homodimers28.
Signaling via all of these receptors is mediated by members of the Janus kinase-signal transducers and activators of transcription (JAK-STAT) family27,75,76 (Fig. 1). JAK2 and either JAK1 or TYK2 appear to mediate phosphorylation of the IL-12 cytokine receptors family-associated STATs. IL-12 mediates signaling via pSTAT477, IL-23 via pSTAT3 and pSTAT469,73, IL-27 via pSTAT1 and pSTAT378,79, and IL-35 via pSTAT1 and pSTAT428. For IL-35, formation of a STAT1:STAT4 heterodimer is required for Ebi2/ Il12a transcription, but partially dispensable for supression28 (PMID:22814351)