Dasatinib blocks histamine release in Btk-deficient basophils. (A,B) Cultured mouse basophils obtained from wild-type (wt) mice (A,C) or Btk-deficient mice (B,D) were preincubated with TNP-specific IgE. Basophils were examined as impure cells (A,B) or as sorted enriched basophils (C,D). Preloaded basophils were washed and incubated in control medium or in medium containing dasatinib (1 μM). Thereafter, cells were exposed to control medium or to TNP (0.1 or 1 μg/mL) at 37°C for 30 minutes. Then, cells were centrifuged at 4°C and lysates and cell-free supernatants examined for the content of histamine by RIA. Results show the percentages of released histamine and represent the means (± SD) from triplicates in one typical experiment each. Analyzing all values in all experiments, the effects of dasatinib on histamine release were found to be significant in wt mice (TNP, 1μg/mL: 28.3% ± 15.1% vs TNP + dasatinib, 1 μM: 5.8% ± 9.8%; P < .05) as well as in Btk-deficient animals (TNP, 1 μg/mL: 16.5% ± 7.3% vs TNP + dasatinib: 3.5% ± 2.1%; P < .05). (E) Basophils from a patient with Btk deficiency were preincubated in control medium (co, ■-■) or dasatinib, 1 μM (▲-▲) for 30 minutes. Thereafter, basophils were washed and incubated in various concentrations of anti-IgE (37°C, 5% CO₂) for 30 minutes. Then, cells were centrifuged at 4°C and the cell-free supernatants and lysates examined for histamine content by RIA. Results show the percentages of released histamine and represent the means (± SD) from triplicates.