Dasatinib inhibits the IgE-dependent up-regulation of activation-linked cell-surface antigens on blood basophils. (A) Peripheral blood cells of healthy donors were preincubated with dasatinib (1 μM) or control buffer for 15 minutes, washed, and then were exposed to control buffer (co) or an anti-IgE mAb (1 μg/mL) for 15 minutes (37°C). Expression of surface antigens on blood basophils was assessed by multicolor flow cytometry as described in the text. Anti-IgE-induced up-regulation of CD antigens was calculated from mean fluorescence intensities (MFIs) obtained with stimulated (MFIstim) and unstimulated (MFIco) cells and was expressed as stimulation index (MFIstim:MFIco). (B) Dose-dependent inhibition of anti-IgE–induced expression of cell surface antigens by dasatinib. Blood basophils were incubated with dasatinib (0.01-1.0 μM) or control buffer for 15 minutes, washed, and then were exposed to control buffer (co) or anti-IgE (1 μg/mL) for 15 minutes (37°C). Expression of CD antigens on basophils was assessed by multicolor flow cytometry. Anti-IgE–induced up-regulation of CD antigens was expressed as stimulation index (MFIstim:MFIco). Results represent the mean (± SD) values of 5 independent experiments (5 donors). Significances in surface marker expression after exposure to anti-IgE are indicated by asterisk (*). (C) Peripheral blood cells of 15 allergic patients were incubated with dasatinib (1.0 μM) or control buffer for 15 minutes, washed, and then exposed to control buffer (control) or to allergens rBet v 1, nDer p 1, or rPhl p 5 (each 1 μg/mL) for 15 minutes (37°C). Expression of CD surface antigens on blood basophils was assessed by multicolor flow cytometry. Allergen-induced up-regulation of CD antigens was expressed as stimulation index (MFIstim:MFIco). (D) Dose-dependent inhibition of allergen-induced expression of cell surface antigens by dasatinib. Basophils were incubated with dasatinib (0.01-1.0 μM) or control buffer for 15 minutes, washed, and then were exposed to control buffer (co) or to various allergens (each 1 μg/mL) for 15 minutes (37°C) as indicated. Allergen-induced up-regulation of CD antigens on basophils was expressed as stimulation index. Results represent the mean (± SD) values of 5 independent experiments (5 donors) for each allergen. Significances in changes in surface marker expression after exposure to allergens are indicated by asterisk (*).