The specificity of radiostaining in crossed radioimmunoelectrophoresis

The major allergen from codfish (DS 22) was used to study specific and non-specific radiostaining in crossed radioimmunoelectrophoresis (CRIE). Various modifications of CRIE experiments were performed including experiments where immunoprecipitates in agarose were transferred to test tubes and the radioactivity was measured in a gammacounter. The degree of non-specific binding of IgE and 125 I-anti-IgE to the percipitates was low. A linear relation was found between the amount of human serum IgE antibody used in CRIE and the degree of radiostaining obtained. Increasing the amount of DS 22 in the precipitates from 0.31 to 2.5 microgram resulted in a moderate increase in the uptake of 125 I-anti-IgE, whereas further increase of the amount of DS 22 (5--10 microgram) resulted in reduced uptake of isotope. Serum from a patient containing IgE antibodies to rabbit serum gave rise to radiostaining over the entire antibody-containing gel area, and it is suggested that such human sera be avoided when using CRIE.