Background: This study was designed to investigate whether the bronchial response to the sensitizing allergen in asthma is correlated with the frequency of allergen-specific T lymphocytes.
Methods: Twenty-three asthmatic patients sensitized to Dermatophagoides pteryonyssinus who had never received hyposensitizing therapy and 11 healthy control subjects were studied. Allergen-specific T lymphocytes were enumerated in peripheral blood with limiting dilution cultures. Bronchial challenge with methacholine was performed in all subjects; patients with asthma also underwent an allergen bronchial challenge. Correlations between allergen-specific T cell frequencies and nonspecific bronchial hyperresponsiveness to methacholine as independent variables and early and late bronchial responsiveness to allergen challenge as dependent variables were investigated by means of stepwise-multiple regression analysis.
Results: We found that the frequency of allergen-specific T lymphocytes was higher than in control subjects in both patients with asthma with (p < 0.001) and those without (p < 0.05) late-phase asthmatic response to allergen. Moreover, the provocative does of allergen necessary to produce an early 15% fall of forced expiratory volume in 1 second could be predicted in part (59%) by an equation that incorporates methacholine sensitivity and allergen-specific T cell frequency.
Conclusions: We conclude that allergen-specific T lymphocytes, which have an established influence on immunoglobulin E production, play an additional role in the induction of the bronchospastic response to inhaled allergen.