Interleukin-33 and Inflammatory Bowel Diseases: Lessons from Human Studies

Figure 1

Representation of IL-33 function in the gastrointestinal mucosa. Full-length IL-33 (30 kDa) is released by a wide range of different cell types, represented here by enterocytes, fibroblasts, and macrophages. IL-33 interacts with lamina propria T cells and determines the production of IL-4, IL-5, and IL-13. IL-13 enhances mucus production by goblet cells, while IL-5 activates eosinophils and B cells, and IL-4 induces Th2 polarization. IL-33 can also activate eosinophils and macrophages, further contributing to a Th2 response in the lamina propria. Neutrophil can release a lighter structure of IL-33 (18–22 kDa), which is known to be more active than the 30 kDa protein. During cellular apoptosis, IL-33 can be cleaved by caspases 3 and 7, generating a 20–22 kDa molecule, a potentially less active protein.