IL-15 and psoriasis: another genetic link to Th17?

Interleukin-15 (IL-15) is a pro-inflammatory cytokine expressed in several inflammatory disorders. Zhang et al. (2007, this issue) report a significant genetic association between IL-15 and psoriasis, which may involve increased stability of IL-15 mRNA. Among its several activities, IL-15 stimulates the expression of IL-17 by T-cells. Together with recent genetic and therapeutic evidence implicating IL-23, these findings suggest a genetic basis for Th17-mediated inflammation in psoriasis.