In vitro histamine release from human basophils triggered by a purified allergen from Dermatophagoides farinae: bimodal aspect of the dose response curve.

Histamine release experiments were performed over a 10(6)-fold range of allergen concentrations on basophils of patients sensitive to Dermatophagoides farinae. Two extracts of D. farinae were used, a partially purified one (Df 80d) containing several allergens and a highly purified component (Ag11). This histamine release patterns obtained with the complex allergen mixture Df 80d gave broad histamine release curves presenting an initial increase, followed by a decrease or a plateau, with occasionally a small dip. The Ag11-induced histamine release curves presented two peaks (bimodal pattern), separated by a more or less pronounced inhibition dip. No non-specific histamine releasing activity was observed with the basophils of two controls. The possible theoretical models for the bimodal histamine release patterns are discussed.