A New Player on the Psoriasis Block: IL-17A-and IL-22-Producing Innate Lymphoid Cells

Innate lymphoid cells (ILCs) are a recently discovered family of innate immune cells belonging to the lymphoid lineage, yet lacking antigen-specific receptors. ILCs were first identified in the intestinal tract, where they contribute to epithelial barrier integrity and host responses to commensal microbes. Teunissen et al. (in the current issue) and Villanova et al. (2014) now suggest an important role for type 3 ILCs (ILC3s) in the skin, particularly in psoriasis. Both groups found an increased frequency of IL-22- and/or IL-17A-producing ILCs in psoriatic skin and blood. These cells are activated in response to IL-1 beta and IL-23, correlate with disease severity, and are decreased following antitumor necrosis factor-alpha (anti-TNF alpha) treatment. The presence of a novel ILC population in psoriatic skin, one that responds to biologic therapeutics, suggests that dysregulation of ILCs is a contributing factor to psoriasis pathogenesis.