Bindability of human IgE to the FcɛRI on human platelets analyzed by flow cytometry. The platelets were (A) untreated (dashed line; only FITC-labeled goat antihuman IgE, solid dark line; human myeloma IgE plus FITC-labeled goat antihuman IgE), (B) pretreated with isotype-matched control Ab (dotted line; only FITC-labeled goat antihuman IgE, dashed line; human myeloma IgE plus FITC-labeled goat antihuman IgE, solid dark line; pretreated with mouse IgG₁), (C) pretreated with mouse MoAb to human FcɛRI  chain (CRA2) (dotted line; only FITC-labeled goat antihuman IgE, dashed line; human myeloma IgE plus FITC-labeled goat antihuman IgE, solid dark line; pretreated with CRA2). These results shown are representative of 10 independent experiments.