CD4 and asthma: Bronchoalveolar lavage fluid (BALF) from asthma patients contains high amounts of IL-4/IL-17A double-positive CD4+ T cells (Wang et al. 2010), and moderate-to-severe human asthma patients have more IL-17A-positive cells in bronchial submucosa than mild asthma patients (Chakir et al. 2003).