FIGURE 1. BAFF-R surface expression on bone marrow B cell populations.

A, Gating strategy identifying BM B lineage cell subpopulations. B lineage cells were first identified with CD19 expression. Mature recirculating B cells were identified through light chain (LC) expression and the absence of CD10, while immature transitional B cells were identified as LC⁺ and CD10⁺. Earlier B lineage cells were LC⁻ and CD10⁺. These early B cells were segregated to a pro-B population characterized by surface CD34, and a pre-B population identified by its lack of CD34. B, The B cell populations were co-stained for the above markers as well as for BAFF-R surface expression or an isotype-matched control antibody. The upper row depicts the BAFF-R surface staining (empty histogram) compared to the isotype control (filled histogram) for that population. The lower row shows a contour plot of the BAFF-R staining in these same populations with gating around the BAFF-R⁺ population. The data are representative of four independently stained bone marrow samples.