Emerging role of interleukin-22 in autoimmune diseases

Abstract

Interleukin-22 (IL-22) is an IL-10 family cytokine member that was recently discovered to be mainly produced by Th17 cells. Previous studies have indicated the importance of IL-22 in host defense against Gram-negative bacterial organisms (in gut and lung). Recently, there is emerging evidence that IL-22 is involved in the development and pathogenesis of several autoimmune diseases, such as systemic lupus erythematosus (SLE), rheumatoid arthritis (RA), multiple sclerosis (MS), Sjögren's syndrome (SS) and psoriasis. Therapeutics targeting IL-22 therefore may have promise for treating various autoimmune diseases. In this review, we discuss the recent progression of the involvement of IL-22 in the development and pathogenesis of autoimmune diseases, as well as its clinical implications and therapeutic potential.

Figure 1. Signaling pathways of IL-22

IL-22 binds as a homodimer at a receptor complex composed of the IL-10R2 and the IL-22R1. IL-22BPacts as a natural, soluble antagonist. Receptor signaling induces the phosphorylation of Jak-1 and Tyk-2, which activates the transcription factor STAT1, and depending on the cell type, also STAT3 and STAT5. MAPKpathway (including MEK1/2, ERK1/2, JNK, and p38) are also activated through a distinct pathway.