Bronchoalveolar lavage cytokine profiles in acute asthma and acute bronchiolitis

Background: The pathogenetic basis for the relationship between acute bronchiolitis and asthma has not yet been completely elucidated. Objective: The aim of this study was to compare these 2 diseases in terms of their patterns of airway cytokine response (TH1 or TH2). Methods: By using a bronchoalveolar lavage (BAL) technique, this study investigated the cytokine levels of BAL fluid in children with acute asthma who had no identifiable respiratory syncytial virus (RSV) infection (n = 18) and in infants with acute bronchiolitis caused by RSV (n = 22). Comparisons were made with normal control subjects (n = 14). IFN-γ (TH1) and IL-4 and IL-5 (TH2) levels were measured in concentrated BAL fluids by means of ELISA. Results: The IL-5 level (P < .001) and IL-5/IFN-γ ratio (P < .001) were significantly increased in the asthmatic group with no identifiable RSV infection and in the RSV-induced bronchiolitis group compared with values in the control group. When infants in the bronchiolitis group were divided into eosinophil-positive and eosinophil-negative subgroups, the eosinophil-positive subgroup had significantly increased IL-5 levels (P < .001) and IL-5/IFN-γ ratios (P < .01) compared with those in the control group, but similar cytokine responses were not induced in the eosinophil-negative subgroup. The percentage of BAL eosinophils correlated significantly with levels of BAL IL-5 in both the asthma group (r = 0.80, P = .000) and the bronchiol-itis group (r = 0.82, P = .000). Conclusions: These findings suggest that a subgroup of the RSV-induced bronchiolitis group results in a TH2-type response, and this could provide a valuable framework to explain the link between RSV-induced bronchiolitis and asthma. (J Allergy Clin Immunol 2003;112:64-71.)