The emergence of the IL-36 cytokine family as novel targets for inflammatory diseases

The recently discovered interleukin (IL)-36 family of cytokines form part of the broader IL-1 family and are emerging as important mediators of inflammatory disease. The IL-36 subfamily consists of three ligands-IL-36 alpha, IL-36 beta, and IL-36 gamma-and the natural antagonist IL-36Ra. The cytokines exert their effects through a specific IL-36 receptor consisting of IL-36R and IL-1RAcP chains. IL-36 cytokines can direct both innate and adaptive immune responses by acting on parenchymal, stromal, and specific immune cell subsets. In humans, inactivating mutations in the gene encoding the IL-36R antagonist, which lead to unregulated IL-36R signaling, lead to an autoinflammatory condition termed deficiency of the IL-36R antagonist, which primarily manifests as a severe form of pustular psoriasis. While such discoveries have prompted deeper mechanistic studies highlighting the important role of IL-36 cytokines in psoriatic skin inflammation, it is now evident that IL-36 cytokines can also play important roles in inflammatory disorders in other organs, such as the gastrointestinal tract and the lungs. Given these emerging roles, strategies to specifically target the expression and activity of the IL-36 family have the potential to uncover novel therapeutic approaches aimed at treating inflammatory diseases in humans.