Specific reactivity of Ba103 with basophils and a subset of mast cells. (A) Reactivity of Ba103 with various cells isolated from hematopoietic and lymphoid organs and tissues of BALB/c mice was analyzed with flow cytometry using lineage-specific markers. Data are shown for basophils (FcϵRIα⁺CD49b⁺) in peripheral blood, spleen, and bone marrow; for mast cells (FcϵRIα⁺c-kit⁺) in skin, intestine, and peritoneal cavity; for neutrophils (Gr-1^high), eosinophils (CCR3⁺), platelets (forward scatter^lowCD49b⁺), and red blood cells (TER-119⁺) in peripheral blood; for peritoneal macrophages (CD11b^bright); and for dendritic cells (CD11c⁺), T cells (CD3⁺), B cells (CD19⁺), and NK/NKT cells (FcϵRIα⁻CD49b⁺) in spleen. Shaded histograms show the staining with isotype-matched control. Similar staining profiles were obtained when cells isolated from C57BL/6 mice were analyzed with Ba103 (data not shown). (B) Bone marrow cells from wild-type and FcRγ chain^−/− C57BL/6 mice were stained for CD49b together with Ba103 or FcϵRIα. The data show the staining profiles of CD49b⁺ bone marrow cells for the surface expression of Ba103 (upper panels) and FcϵRIα (lower panels). Shaded histograms show the staining with isotype-matched control. The numeral in each panel shows the percentage of Ba103⁺ cells.