Interleukin-25: a two-edged sword in the control of immune-inflammatory responses.

Interleukin-25 (IL-25), the newest member of the IL-17 cytokine family, initiates, promotes, and augments Th2 cell-mediated immune responses, thereby contributing to allergic disease and defense against helminthic parasites. More recent studies have shown that IL-25 can control the functional activity of non-T cells and suppress the initiation and progression of immune-mediated pathologies such as endotoxemia, colitis, experimental autoimmune encephalomyelitis, and diabetes. Taken together with the fact that IL-17 family members can form homo and heterodimers with different functions, the IL-17 family encapsulates the subtle pro and anti-inflammatory function of cytokines, which need to be understood before anti-cytokine therapy can be exploited rationally in the clinic.