Quantitation of IgE antibody specific for ragweed and grass allergens: Binding of radiolabeled allergens by solid-phase bound IgE

IgE antibody specific for multiple allergens extracted from grass and ragweed pollens was measured by radioimmunoassay. The assay depends on the interaction between IgE antibody bound to a polystyrene solid phase, ¹²⁵I-labeled grass allergens (GA), and ragweed allergens (RW). The binding of ¹²⁵I RW by serum IgE antibody from 37 allergic patients ranged from 0.2 ng to 75 ng RW protein (P) bound per ml. This binding of ¹²⁵I RW by patient's IgE was paralleled by their IgE binding of ¹²⁵I antigen E (AgE), a purified allergen from ragweed pollen (r = 0.90, p < 0.001). Inhibition of patient's IgE binding of ¹²⁵I RW by highly purified AgE ranged from 25% to 85% indicating individual differences in patient's IgE response to inhaled ragweed pollen. The binding of ¹²⁵I GA by serum IgE antibody from 7 grass-sensitive patients ranged from 0.6 ng GA P bound per ml to 15 ng. This assay should be useful in the study of IgE responses to environmental agents containing multiple allergens and has the advantage that other antibody classes cannot interfere with the interaction between IgE antibody and labeled allergens.