Historically, IL-17 was considered to be derived from conventional TH17 cells; however, a novel CD4+ TH2 memory or effector cell subset that collectively expresses GATA3 and RORγt and produces TH2 and TH17 cytokines has now been identified; this subset persists as the predominant IL-17-producing T cell population during the chronic phase of asthma (135). This evidence concerns the gene CD4 and asthma.