Isolated airways from current smokers are hyper-responsive to histamine

Background Epidemiological studies suggest that bronchial hyper-responsiven ess (BHR) and elevated levels of serum IgE are more frequently found in cur rent smokers than in ex-smokers. Objective Since elevated serum IgE is associated with BHR under both in viv o and in vitro conditions, we aimed to assess whether smoking affects BHR i ndependently from IgE. Methods Lung resection material was obtained from 27 current smokers and 11 nonsmokers with low serum IgE (< 100 U/mL). Peripheral airways were cut in to rings and incubated overnight in the presence (passively sensitized) or absence (non-sensitized) of serum containing IgE levels above 250 U/mL. Iso metric contractile responses to histamine were assessed in the organ bath. Results Compared with non-smokers, isolated airways from smokers showed sig nificantly increased responses to histamine (P < 0.05, ANOVA). Passive sens itization enhanced responses in both groups by about the same amount (P < 0 .05, both). Conclusions In patients with low serum IgE current smoking is associated wi th increased bronchial responsiveness to histamine in vitro, which can be f urther enhanced by passive sensitization. These findings suggest that both smoking and serum IgE contribute to nonspecific airway hyper-responsiveness .