Basophil and mast cell counts in Irf8^−/− mice. (A,C) Flow cytometric analysis of basophils (A) and mast cells (C) in WT and Irf8^−/− mice. Representative flow cytometry data are shown. Values in the bar graphs are means ± standard deviations from 5 to 7 mice of each genotype. (B) RT-qPCR analysis of Mcpt8 and Il4 in freshly isolated, unstimulated WT and Irf8^−/− bone marrow cells. Values in the bar graph are means ± standard deviations from 3 mice of each genotype. (D) Representative toluidine blue–stained sections of ear pinnae (left). The arrowheads indicate typical mast cells. Insets show high magnification. Bars represent 50 μm (D). The mast cells in toluidine blue–stained sections were counted and normalized per unit area (mm²) of tissue examined (right). (E) Toluidine blue–stained sections of the stomach were counted as described in (D). Values in the bar graphs are presented as the mean ± standard deviation of sections derived from 3 mice of each genotype. ***P < .001 (Student t test). NS, not significant.