IL17A and infection: Cathelicidin deficiency is highly associated with infection and asthma exacerbations.[34] Moreover, vitamin D prevents production of Th1-associated cytokines and interleukins like IL-17, thus induces inflammation reduction and smooth muscle cell proliferation.[31] Furthermore, new studies showed that hypovitaminosis D are linked with increased pro-inflammatory cytokine expression, improving pro-inflammatory influence in asthmatic patients.