Importantly, it was also shown in vitro that IL-17A, IL-17F and IL-22 cytokines could exert a direct chemotactic activity on airway smooth muscle (ASM) cells; hence, augmented ASM cell mass and tissue remodeling of the airways in severe asthma and COPD patients could be explained in part, by the infiltration of ASM cells elicited by Th-17-associated cytokines [23]. Here, IL17A is linked to chronic obstructive pulmonary disease.