For example, in high-density microarray studies of gene expression in the airway epithelium in asthmatic subjects and healthy controls, we recently found that periostin is among the most highly up-regulated genes in asthma and that its expression in airway epithelial cells is regulated by interleukin 13 (IL-13), a Th2 cytokine 2. The gene discussed is IL13; the disease is asthma.