IL-13 is also directly related to the airway mucus production by identifying signaling pathways activated in COPD involving IL-13R, calcium-activated chloride channel regulator1(CLCA1), and mitogen-activated protein kinase13 (MAPK13), which regulates the expression of MUC5AC gene in human airway epithelial cells [3, 57, 58]. This evidence concerns the gene MUC5AC and chronic obstructive pulmonary disease.