[Recent progress in the pathophysiological role of interleukin-19]

Cytokine signal is essential for the biological function including development, maintenance of homeostasis and progression of disease. There are growing evidences that signaling via pro-inflammatory cytokines underlie a variety of immunological diseases such as psoriasis, atopic dermatitis, inflammatory bowel disease, and metabolic syndromes, in which cytokine signals are known as a potential therapeutic target of antibody drugs. In contrast, anti-inflammatory cytokines, which is represented by IL-10, largely contribute to suppression of inflammation and restoration of injured tissues. IL-19 is a member of IL-10 cytokine family, which comprises IL-20 cytokine subfamily with IL-20, IL-22, IL-24, and IL-26. IL-19 is produced by myeloid and epithelial cells with stimulation of bacterial components and cytokines. Although IL-19 has been originally recognized as a potential Th2-related cytokine, in recent researches, it has been reported that this cytokine upregulates Th17 response to reflect and promote progression of Th17-related disease including psoriasis. On the other hand, IL-19 has anti-inflammatory effects on inflammatory diseases such as infectious skin disease, inflammatory bowel disease, and cardiovascular disease. Therefore, IL-19 may exert pleiotropic effects dependent on the pathological mechanism of inflammatory diseases. In this review, we summarize recent studies about IL-19 and introduce the pathophysiological and therapeutic role of IL-19 in inflammatory diseases.