Background: Activated T helper lymphocytes are present in the airway and their production of cytokines is important in the pathogenesis of asthma, however, the relationship between T helper lymphocyte-derived cytokines and airway cough reflex sensitivity remains unknown.
Methods: The effect of the orally active Th2 cytokine inhibitor suplatast tosilate on cough response to inhaled capsaicin was examined in eleven patients with stable atopic asthma and compared with patients having non-atopic asthma and chronic bronchitis (the latter of which is not related to Th2 cytokines). Capsaicin cough threshold, defined as the lowest concentration of capsaicin eliciting five or more coughs, was measured as an index of airway cough reflex sensitivity. Concentration of serum total IgE level was also measured after treatment with suplatast tosilate.
Results: The cough threshold after two weeks treatment with suplatast tosilate was significantly greater than the value with placebo accompanied by decrease of serum IgE level in atopic asthmatics. This significance was not observed in patients with non-atopic asthma or chronic bronchitis.
Conclusions: Th2 cytokines may be possible modulators augmenting airway cough reflex sensitivity in atopic asthmatic airways but not in non-atopic asthmatic or bronchitic airways.