Figure 1.

Effects of IL-33 on the activation of eosinophils, basophils, mast cells, DCs, ILC2 cells, and T cells in allergic inflammation. IL-33 is normally sequestered in the nucleus of various cells via nuclear-localization and chromatin-binding motifs in its amino terminus. After the cells are damaged, under stress, or stimulated by allergens, full-length IL-33 is released extracellularly, but it has low activity as a cytokine. Mast cells proteases and some allergens possess protease activity and can directly process IL-33 by cleaving within the protease-sensor domain to generate a more potent cytokine domain, which will directly activate local and infiltrating basophils, mast cells, group 2 innate lymphoid cells (ILC2), T cells, and eosinophils to induce allergic inflammation.