Interleukin-22 (IL-22), a cytokine belonging to the IL-10 family. IL-22 is primarily produced by immune cells, including Th17 cells, Th22 cells, group 3 innate lymphoid cells (ILC3s), and certain subsets of NK and T cells. Its receptor, however, is selectively expressed on non-hematopoietic epithelial and stromal cells (e.g., in the skin, synovium, lungs, and gastrointestinal tract). IL-22 plays a dual role: it is crucial for tissue repair and host defense at barrier surfaces, but its dysregulated or excessive production is strongly implicated in the pathogenesis of autoimmune and chronic inflammatory diseases.