In vitro IgE eluation and histamine releasability from peripheral leukocytes of atopics and normals

The relation between the amount of cell-bound IgE and the histamine 'releasability' of peripheral leukocytes was studied in 28 patients with atopic diseases and 26 non-atopic controls after in vitro stimulation with anti-IgE. Cell-bound IgE was eluted in acid buffer (pH 3.7) and the amount of histamine released (HR) into supernatant at this pH was measured. Incubation with acetate buffer (pH 3.7) induced significantly higher spontaneous HR (32 net percent) in atopics compared to 18% in controls. The amount of IgE eluted was significantly higher in atopics: The calculated number of IgE molecules/basophil was 332,000 in atopics compared to 177,000 in controls. There was a significant positive correlation between plasma IgE and in vitro elutable IgE in atopics (r = 0.73) compared to controls (r = 0.24). After a careful washing procedure attempts were made to 'resensitize' the basophils through incubation with autologous plasma or standard IgE solutions. When resensitization was possible, there was no correlation between histamine releasability after resensitization and original IgE content of basophils. It is concluded that the increased histamine releasability from leukocytes of atopic individuals after stimulation with anti-IgE is only in part due to an increased number of IgE molecules per basophil surface. A non-specific increased releasability was demonstrated by increased spontaneous HR rates in acid buffer (pH 3.7). A resensitization with autologous plasma-IgE was possible only in half of the subjects investigated, most of them being atopic. The data support the concept of an altered releasability both towards IgE-dependent and independent stimuli being one possible factor in the pathogenesis of atopic eczema.