Transient basophil depletion induced by antibody 2.4G2 and 2.4G2 scFv-MSA. Mice were bled before treatment and 4 and 24 hours after treatment with 0.43 nmol (65 µg) 2.4G2 or equimolar amounts of 2.4G2 scFv-MSA or HSA. Ammonium chloride buffer was used to lyse RBCs before PMBCs were stained with anti-CD49b-Pacific Blue, anti-FcεRIα-PerCP/Cy5.5, and anti-CD200R3-FITC. Stained samples were analyzed by MACS Quant, and data were analyzed by Flowjo V10 software. Basophils were identified as CD49 dim, FcεRIα positive, and CD200R3 positive. A round gate is used to mark basophil population. The frequency represents the percentage of basophils within the whole PBMC population shown as P1 in Figure 5A. Basophil concentrations (per microliter blood) represent in vivo concentrations. Histograms are representative of 6 to 7 mice per group from 4 independent experiments.