The interaction of human and rodent IgE with the human basophil IgE receptor

The cross-reactivity of the human IgE receptor with mouse and rat IgE was studied. Using leukocytes from a patient with chronic myelogenous leukemia, in which the mononuclear fraction contained up to 75% basophils, both rat and mouse IgE were found to inhibit the binding of ¹²⁵I-human IgE to the human basophilic leukemia (HBL cells). About 15-fold more rodent IgE were required for 50% inhibition of binding than unlabeled human IgE (hIgE). Dose-response studies using increasing amounts of rodent vs human ¹²⁵I-IgE indicated that HBL cells had about 8,000 receptors per cell for hIgE and 5,500 receptors per cell for rodent IgE. When the HBL cells were surface labeled with ¹²⁵I and subsequently solubilized with non-ionic detergent, the labeled hIgE receptor could be isolated by either affinity chromatography on IgE-Sepharose (either human or rodent) or by immunoprecipitation with hIgE and anti-IgE. By SDS-PAGE on 10% gels, the receptor had a m.w. of 58,000 daltons. The solubilized receptors exhibited some rebinding to hIgE-Sapharose, and this rebinding could be inhibited by either human or rodent IgE but not by human IgG. Both the HBL cells and normal human basophils could be passively sensitized with murine IgE anti-DNP for antigen-induced histamine release. The minimum concentration of the mouse IgE antibody for sensitizing normal basophils was 20 to 200 ng/ml. Pretreatment of basophils with human IgE, but not human IgG, abrogated the capacity of the murine IgE antibody to sensitize the cells for histamine release, which indicated that the human and rodent IgE were interacting with the same receptor.