Background The models for exposure to house dust in research and clinical practice are selected with respect to their role in IgE-mediated immediate hypersensitivity. The use of isolated major allergens instead of complex allergen extracts is becoming increasingly popular as it offers some important advantages for quantitative measures in diagnosis and research.
Objective To compare house dust mite extract and isolated mite major allergens with respect to their ability to induce early and late asthmatic responses and bronchial hyperreactivity.
Methods Bronchial responses to house dust mite (HDM, Dermatophagoides pteronyssinus) extract and isolated major allergens from HDM (Der p 1 and Der p 2) were compared in a double-blind, randomized, cross-over study in 20 patients with mild to moderate asthma who were allergic to HDM. Allergen was titrated to a standardized early asthmatic response. Bronchial hyper-responsiveness to histamine (PC20histamine) was determined before and after allergen inhalation to assess allergen-induced bronchial hyper-responsiveness and IL-5 was measured in serum. In addition, the allergens were applied in intracutaneous skin tests and activation of basophil leucocytes and proliferation of peripheral blood mononuclear cells was tested in vitro.
Results After a similar early asthmatic response (mean Δforced expiratory volume in 1 s (FEV1),max−29.4 (SD 7.2) vs. −33.1 (8.6) %; mean difference 3.6 (95% CI −0.9 to 8.2) %), the late asthmatic response (mean ΔFEV1,max−45.9 (21.9) vs. −32.7 (22.3) %; mean difference 13.2 (3.8–22.3) %), the degree of allergen-induced bronchial hyper-responsiveness (mean ΔPC20histamine, 1.8 (1.0) vs. 1.2 (0.9) doubling dose; mean difference 0.6 (0.2–1.1) doubling dose) and serum IL-5 at 6 h were found to be significantly higher after bronchial challenge with HDM extract than after challenge with an isolated HDM major allergen. Likewise, there was an increased late skin reaction with HDM compared with isolated major allergen after a similar early skin reaction.
Conclusion Constituents of HDM extract, other than Der p 1 or Der p 2, with no significant influence on the IgE-mediated early asthmatic response contribute significantly to the allergen-induced late asthmatic response and bronchial hyper-reactivity.