IL17A and asthma: In addition, it was found that Th17 cells and IL‐17 promoted eosinophil and neutrophil expression in AR and asthma patients, indicating the dominant role in allergic inflammatory response.[62] The elevated levels of IL‐17 mRNA, as well as IL‐17 protein, have been found in the lungs, sputum, tracheal aspirate, bronchoalveolar lavage, and sera from asthmatic patients, and IL‐17 was also related to resistance to steroids.