Effect of brentuximab-vedotin on IgE-dependent HR and activation in human BAs and MCs. (A-B) BAs obtained from healthy donors (n = 3) (A) and CD30⁺ or CD30⁻ MCs from patients with mastocytosis (ASM, n = 2; MCL, n = 3; SM-AHNMD, n = 1) (B) were preincubated in control medium (Co) or in various concentrations of brentuximab-vedotin as indicated at 37°C for 30 minutes. Afterward, cells were exposed to anti-IgE (1 µg/mL) at 37°C for 30 minutes. After centrifugation, histamine concentrations were determined in supernatants and cell lysates. Histamine release is expressed as percentage of total histamine. Results represent the mean ± SD from 1 representative experiment (A; left panel) and represent the mean ± SD from 3 normal donors (A, right panel) and from 3 patients with mastocytosis in each panel (B). *P < .05. (C) BAs in whole-blood samples (n = 4) were preincubated in control medium (Co) or in medium containing various concentrations of brentuximab-vedotin (0.1-10 µg/mL) at 37°C for 30 minutes. Then, cells were exposed to anti-IgE antibody (1 µg/mL) for another 15 minutes (37°C). Thereafter, cells were stained with mAb directed against CD63 (left panel) or CD203c (right panel), and analyzed by multicolor flow cytometry as described in the “Material and methods.” BAs were defined as CD203c⁺ cells in all samples. Anti-IgE-induced upregulation of CD antigens was calculated from mean fluorescence intensities (MFIs) obtained with stimulated (MFIstim) and unstimulated (MFIcontrol) cells, and was expressed as SI (MFIstim: MFIcontrol). Results show SI values and represent the mean ± SD from 4 donors.