IL17A and chronic obstructive pulmonary disease: Furthermore, IL‐17 can increase the expression of p53 and PAI‐1, as well as increase C–X–C motif chemokine ligand 1 (CXCL1), CXCL2, and C–X–C chemokine receptor 2 to induce neutrophil influx, hence enhancing the neutrophil inflammatory reaction in COPD.