Notably, the combined presence of T1 and T2 immune responses appears to be a hallmark of the sickest of asthma patients (31, 35, 37), with IFN-γ or the T1 phenotype negatively associating with airway obstruction, as measured by the percentage of predicted forced expiratory volume in 1 second (FEV1), a measure of lung function (10, 40). The gene discussed is IFNG; the disease is asthma.