Biology of recently discovered cytokines: Discerning the pro- and anti-inflammatory properties of interleukin-27

IL-27 is a recently identified heterodimeric cytokine produced in response to microbial and host derived inflammatory cues. Initial studies indicated that IL-27 promotes the generation of Th1 responses required for resistance to intracellular infection and unveiled the molecular mechanisms mediating this effect. However, subsequent work uncovered a role for IL-27 in the suppression of Th1 and Th2 responses. Thus, by discussing its pleotropic functions in the context of infection-induced immunity and by drawing parallels to fellow IL-6/IL-12 family cytokines, this review will attempt to reconcile the pro- and anti-inflammatory effects of IL-27.