Passive sensitization of human basophils: evidence for heterogeneity in the IgE molecule.

Possible functional heterogeneity of human IgE antibody was studied by passively sensitizing human basophils for antigen-induced histamine release. Six sera of known IgE anti-ragweed antigen E and total IgE content were diluted to contain 10 ng of antibody but differed with respect to the ratio of specific/total IgE. The relative ability of the sera to passively sensitize generally reflected the specific/total IgE ratio but one serum was 2.5 times more active than the remainder. This ability did not reflect the IgG antibody level nor was it due to a dialyzable or heat-stable factor. These data indicate functional IgE heterogeneity, probably due to the interaction of the Fc portion of IgE with the basophil receptor.