IL-31 and its role in mucosal diseases
Multiple studies have established a role for members of the IL-6 family in the regulation of epithelial cell function in lung, skin and gastrointestinal tract (GIT).43–45 Mucosal epithelial cells express OSMRβ that can be activated by IL-31 and OSM.5 While the downstream effect of OSM interaction with its cognate receptor is well-described,46,47evidence is emerging for a significant role of IL-31 mediating inflammatory processes at mucosal sites. Mucosal sites are protected by an epithelial barrier, which senses incoming pathogens or allergens, and can respond to these by release of “alarmins” including IL-33, a cytokine of the IL-1 family which signals through its cognate T1/ST2 receptor connecting epithelial sites with the immune system by activating eosinophils, mast cells and TH2 lymphocytes.48,49 In particular IL-33-driven activation of TH2 lymphocytes results in effective secretion of IL-31 from T cells, which can subsequently activate IL31RA/OSMRβ+ epithelial cells, neurons and tissue-residing immune cells.