Immunolocalization of the FcɛRI in human platelets. Localization of the FcɛRI  chain in human platelets was examined by immunoelectromicroscopy after staining with the antihuman FcɛRI  chain MoAb (CRA1), using the indirect immunoperoxidase method. (A) FcɛRI  chain was localized to the cell-surface (arrow head) of human platelets. (B) Negative control with isotype-matched control Ab shows no cell-surface staining.