Patients having more severe asthma tended to possess more IFN-γ-positive and IL-17A-positive CD4-positive T cells in bronchoalveolar lavage (BAL) fluids [53], and there was an inverse correlation between the numbers of TH1-enriched CD4-positive T cells in BAL cells and the percent predicted forced expiratory volume in 1 s (FEV1) in severe asthma patients [54]. The gene discussed is IL17A; the disease is asthma.