Increased Interleukin-4 and Decreased Interferon-<b>γ</b> in Exhaled Breath Condensate of Children with Asthma

Exhaled breath condensate analysis for noninvasive quantification of airway inflammation in asthma is a potentially useful research tool in children. There is an imbalance between T-helper (Th)-2 cells, which secrete interleukin (IL)-4, and Th1 cells, which secrete interferon (IFN)-γ, in asthma. We measured concentrations of IL-4 and IFN-γ in breath condensates of 37 children (11 normal, 12 steroid-naive, and 14 steroid-treated children with asthma). Exhaled IFN-γ was significantly lower in steroid-naive and steroid-treated children with asthma compared with normal control subjects (3.7 ± 0.2 versus 5.1 ± 0.4 pg/ml, p < 0.01 and 4.1 versus 5.1 pg/ml, p < 0.05). By contrast, mean exhaled IL-4 was elevated in asthma (53.7 ± 4.2 pg/ml) compared with normal children (35.7 ± 6.2 pg/ml, p < 0.05) and concentrations were lower with steroid treatment (37.5 ± 5.6 pg/ml, p < 0.05). Exhaled IL-4 was significantly lower in children with asthma on more than 600 μg inhaled steroid/day. The IL-4/IFN-γ ratio was significantly greater in children with asthma compared with control children and the children with asthma on inhaled steroid therapy. We have shown for the first time that IFN-γ and IL-4 can be assayed in exhaled breath condensate and shows an increased ratio of IL-4/IFN-γ, consistent with predominance of Th2 cells in airways of children with asthma. Exhaled breath condensate analysis may have a useful role in studying allergic inflammation in childhood asthma.