Expansion of basophils in IRF-2^-/- mice. (A) Flow cytometry for splenic basophils (FcϵRIα⁺Dx5⁺c-kit^-B220^-). Numbers represent the percentages of c-kit^- cells within B220^- cells. (B) Percentages of FcϵRIα⁺B220^- cells in the spleen derived from control (○) and IRF-2^-/- (•) mice, representing 16 litters. Values are significantly different between these 2 groups of mice (P < .001). (C) Morphology of freshly isolated basophils. Bars = 10 μm. (D) Mononuclear cells derived from the liver, peripheral blood (PBL), or BM were stained as in panel A. Numbers represent the percentages of FcϵRIα⁺B220^- cells.