Depletion of basophils but not mast cells by the in vivo administration of Ba103. (A and B) BALB/c mice were treated with an intravenous injection of 30 μg Ba103 or control rat IgG. A day later, peripheral blood cells, spleen cells, and bone marrow cells were isolated and stained for FcϵRIα and CD49b to identify basophils, while cells isolated from the ear skin and peritoneal cavity were stained for FcϵRIα and c-kit to identify mast cells. Representative staining profiles from flow cytometry are shown in panel A. Profiles of staining with isotype-matched control antibodies are also shown for mast cells. The numeral in each panel shows the percentage of basophils or mast cells. In panel B, the cell number or frequency of basophils and mast cells in each organ and tissue from the mice treated with Ba103 (■) or control IgG (▩) is summarized. Data are expressed as the mean (± SEM) of 5 mice in each group and are representative of 3 repeated experiments. (C) Mast cell–deficient WBB6F1-W/W^v mice were treated and analyzed as in panel A. The number of basophils in peripheral blood and spleen 1 day after treatment is shown as in panel B. Data are expressed as the mean (± SEM) of 5 mice in each group and are representative of 2 repeated experiments.