CD4 and asthma: We observed a slight but significant deficiency of BAL CD4+FOXP3+ Treg cells in asthmatic patients (median frequency, 5.3%; IQR, 4.3% to 8.2%) compared with those in healthy subjects (8.1%; IQR, 5.6% to 10%; P = .03; Fig 1, C), which was restricted to patients with severe asthma (Fig 1, C) and was not evident in blood, sputum, or bronchial biopsy specimens.