IL33 and idiopathic pulmonary fibrosis: For example, the cytokines IL-25 and IL-33 produced by epithelial cells induce Th2-type adaptive responses where increased expression of both cytokines has been found in patients with idiopathic pulmonary fibrosis (IPF) [40,41,42], and IL-33 has an inhibitory effect on mast cell functions [43].