Affinity of IgE antibody to antigen influences allergen-induced histamine release

Background Although affinity of an antibody for an antigen is recognized to be an important factor in determining its biological effects, little is known about the relevance of such affinity of IgE antibodies to the functional response. Objectives To investigate the effect of IgE antibody affinity to Der p 2 on Der p 2-induced histamine release from human basophils. Methods The most probable value of the dissociation constant (Kd) of IgE antibody to Der p 2 was calculated and histamine release by Der p 2-challenged leucocytes was used to evaluate the biological efficacy of the IgE antibody. Results The most probable Kd value of IgE antibody to Der p 2 ranged from 5.6 to 177.8 pM in 14 asthmatic patients sensitive to Der p 2. A significant correlation was observed in Der p 2-induced histamine release between the sensitivity and the Kd value for Der p 2-specific IgE antibody (r(s) = 0.797, P = 0.0040), suggesting that the higher the affinity, the lower the amount of allergen required for the release of a specific level of histamine. Conclusion Apart from the changes associated with the reactivity, the sensitivity of histamine release is closely related to the affinity of IgE antibody for its antigen.