Background Eosinophilic tracheobronchitis with cough hypersensitivity, abbreviated as atopic cough, is an important cause of chronic cough. The reason for the absence of airway hyper-responsiveness is unknown, differing from asthma, a Th2 cytokine-mediated disorder.
Objective To compare the type 1 helper T cell (Th1)/Th2 balance in the peripheral blood from subjects with atopic cough and atopic asthma, we assessed the intracellular cytokine production at the single-cell level.
Methods Thirty-six subjects (10 patients with atopic cough, 18 with atopic asthma, and eight control subjects) were included. Intracellular IL-4 and IFN-γ were detected in CD4+ T cells by flow cytometry.
Results A significantly lower ratio of IFN-γ-/IL-4-producing CD4+ T cells after phorbol 12-myristate acetate/ionomycin stimulation was found in patients with atopic cough and atopic asthma compared with normal subjects. In comparison between atopic patients, the ratio of IFN-γ-/IL-4-producing cells was significantly higher in atopic cough than in atopic asthma. However, the proportion of IL-4-producing CD4+ T cells was significantly higher in patients with atopic asthma than in normal control subjects and no significant difference was detected between patients with atopic cough and normal subjects. No significant difference in the proportion of IFN-γ-producing cells was found between the subjects. Overall, the total IgE levels were positively correlated to the IL-4-producing cells and inversely correlated to the ratio of IFN-γ-/IL-4-producing cells.
Conclusion These results show the lower degree of Th2 cytokine predominance in atopic cough compared with atopic asthma and suggest the relation between the Th1/Th2 balance and atopic status.