CCL17 and asthma: Th2-asthma (i.e., eosinophilic asthma) is well established to play a leading role in asthma development, as more than half of asthma cases have a Th2 phenotype, where M2 macrophages predominantly secrete high levels of IL-13 and chemokines (e.g., CCL-17 and CCL-18), inducing airway eosinophil infiltration and mucus hypersecretion and contributing to lung function impairment and airway remodelling (38, 39).