Opposing roles for IL-13 and IL-13 receptor alpha 2 in health and disease

Interleukin (IL)-13 is a key inducer of several type-2 cytokine-dependent pathologies. It regulates inflammation, mucus production, tissue remodeling, and fibrosis. Consequently, it has become an important therapeutic target for a number of debilitating illnesses, including asthma, idiopathic pulmonary fibrosis, ulcerative colitis, as well as several other diseases in which IL-13 is believed to be overproduced. In the murine model of schistosomiasis, IL-13 has emerged as a central mediator of chronic infection-induced liver pathology. Although IL-4, IL-5, IL-10, and IL-13 each regulate distinct aspects of the granulomatous inflammatory response, IL-13 was identified as the primary mediator of liver fibrosis. Thus, elucidating the mechanisms that regulate the production and function of IL-13 has become an intensive area of research. IL-13 signaling is mediated by the type-2 IL-4 receptor, which consists of the IL-4R alpha and IL-13R alpha 1 chains. However, another IL-13-binding chain, IL-13R alpha 2, appears to strongly inhibit the activity of IL-13. Animals deficient in IL-13R alpha 2 fail to downmodulate granuloma formation in the chronic phase of infection. They also develop severe IL-13-dependent fibrosis and portal hypertension and quickly succumb to the infection. Here, we summarize findings from the schistosomiasis model, which illustrate opposing activities for IL-13 and IL-13R alpha 2 in health and disease.