Structure of IL-35
IL-35 is reportedly composed of two subunits p35 and EBI3, which are shared with other IL-12 family members, namely IL-12 and IL-27, respectively. p35, which is related to IL-6 and G-CSF, is secreted in response to IFNγ and agonists of TLR3, 4, or 7. In contrast, expression of this subunit is inhibited by Th2 cytokines. EBI3 is a 34-kDa glycoprotein that was first identified in B cells following Epstein-Barr virus infection, and is homologous to the p40 subunit of IL-12 and IL-23. Studies also indicate that EBI3 exists independently of other subunits and as a heterodimer with p28 (IL-30) to form IL-27. The exact mechanism underlying the formation and production of IL-35 remains under investigation.
Function of IL-35
The biology of IL-35 is not well understood. Nevertheless, the expression and function of this cytokine may be unique among the IL-12 family members. Studies suggest that IL-35 is produced by regulatory T cells (Tregs) and functions to suppress inflammation. IL-35 may mediate this effect by influencing the proliferation and function of effector T cells.