STAT3 and inflammatory bowel disease: In laminar propria lymphocytes of inflammatory bowel disease patients, LIF-activated STAT4 inhibits activation of the STAT3-dependent Il17a/Il17f promoter, while in intestinal epithelial cells, LIF bypasses abnormally low STAT4 levels and induces YAP gene expression by activating STAT3 (Zhang et al., 2019).