Interleukin-33 in health and disease.

Interleukin-33 (IL-33) - a member of the IL-1 family - was originally described as an inducer of type 2 immune responses, activating T helper 2 (T2) cells and mast cells. Now, evidence is accumulating that IL-33 also potently stimulates group 2 innate lymphoid cells (ILC2s), regulatory T (T) cells, T1 cells, CD8 T cells and natural killer (NK) cells. This pleiotropic nature is reflected in the role of IL-33 in tissue and metabolic homeostasis, infection, inflammation, cancer and diseases of the central nervous system.