Sensitivity to the house dust mite and airway hyperresponsiveness in a young adult population

Background: The pathogenic mechanisms of airway hyperresponsiveness (AHR) i n asthma are unknown and only a few studies have examined the importance of sensitivity to antigens in AHR in young adults. Objective: We investigated the correlation between AHR and sensitivity to s pecific antigens, atopy, history of childhood asthma and spirometry in a yo ung adult population. Methods: Based on the results of interviews with 447 students at our univer sity, 308 non-smoker students were classified into six groups. Group 1 comp rised subjects with intermittent mild bronchial asthma; group 2, subjects w ith history of childhood asthma; group 3, subjects with atopic disease, and a RAST score for Dermatophagoides farinae (Def) of greater than or equal t o 2; group 4, normal subjects with a RAST score for Def of greater than or equal to 2; group 5, subjects with cedar pollinosis; and group 6, normal su bjects. We measured AHR to methacholine (MCh), spirometry, immunoglobulin E -radioimmunosorbent test (IgE-RIST), IgE-radioallergosorbent test to six co mmon antigens, eosinophil cationic protein (ECP), and eosinophil count in p eripheral blood in each subject. Results: Airway hyperresponsiveness to MCh did not correlate with IgE-RIST, eosinophil count, or ECP. The highest AHR to MCh was present in groups 1 a nd 2 and lowest in groups 5 and 6. Multiple regression analysis showed that sensitivity to Def was the only factor that significantly influenced AHR t o MCh. Airway hyperresponsiveness to MCh of groups with a RAST score for De f of 0/1 was lower than groups with a RAST score of 2 to 6. Airway hyperres ponsiveness to MCh did not correlate with the degree of positivity to Def a ntigen among positive sensitized groups (RAST score 2 to 6). Conclusions: Sensitivity to mite antigen may be important in the pathogenes is of AHR and Def is a major contributing antigen in young adults in Japan. Once asthma occurs, AHR remains positive for a long time even after the di sappearance of asthma-related symptoms.