In patients with severe asthma, IL-5 levels were also significantly increased in both BAL fluid (0.015 pg/mL; IQR, 0.007-0.19 pg/mL; P < .05) and sputum (6.18 pg/mL; IQR, 3.13-14.8 pg/mL) compared with levels seen in healthy subjects (1.19 pg/mL; IQR, 1.0-2.2 pg/mL; P = .005; see Fig E4, B), suggesting that its secretion might be relatively steroid insensitive and might be derived from cellular sources other than airway TH2 cells. Here, IL5 is linked to asthma.