Intracellular calcium response induced by HRF/TCTP. Purified basophils were labeled with Fura 2, and calcium was measured by digital videomicroscopy as described in “Methods.” Basophils from 2 HRF/TCTP-R donors were stimulated with 24 μM HRF/TCTP (○) and from 2 HRF/TCTP-NR (●). Basophils from 2 HRF/TCTP-R were stimulated with 0.1 μg/mL AIgE (small dashed line) and from 2 HRF/TCTP-NR donors (large dark dashed line).