CCL17 and inflammatory bowel disease: CCR4 is a highly specific receptor for two CC chemokine ligands CCL17 (thymus- and activation-regulated chemokine) and CCL22 (macrophage-derived chemokine) (Yoshie, 2021), which were shown to be expressed in mesenteric lymph nodes (LNs) in a mouse model of inflammatory bowel disease (Yuan et al., 2007) and lung tissues affected by allergic airway inflammation (Faustino et al., 2013).