Th17 cell cytokines such as IL-17A and IL-22 have also been reported to enhance neutrophilic airway inflammation and Th2 cell-mediated eosinophilic airway inflammation in asthma, and are thought to contribute to the severity of asthma by enhancing eosinophil recruitment into the airways and mediating Th2-cell differentiation (Wakashin et al., 2008). This evidence concerns the gene IL22 and asthma.