Figure 1. The IL-12 cytokine family; their structure and activated signaling pathways.
IL-12, IL-23, IL-27 and IL-35 are heterodimeric cytokines that belong to IL-12 family. These IL-12 family siblings comprise of both common as well as unique subunits and binding receptors. In addition to their structural relationship, the IL-12 family members activate overlapping JAK/STAT signaling pathways which explains some of their mutual characteristics. IL-12, IL-23 and IL-27 structure, expression and mechanism of action is well studied and our knowledge about IL-35 is rapidly growing.