Kinetics and comparative mouse B-cell reduction after treatment with anti-BR3 mAb, BR3-Fc, or anti-CD20 mAb. Mice (≥ 5/group) treated with anti-BR3 mAb (200 μg/week), BR3-Fc (150 μg × 3/week), or anti-CD20 mAb (200 μg/week) were analyzed at different times, with B-cell numbers and subsets evaluated by flow cytometry. Anti-BR3 treatment reduced blood B cells (expressed as percentage of baseline absolute cell counts) faster and more profoundly than BR3-Fc but slower than anti-CD20 treatment (A). By day 15 of treatment, the extent of B-cell reduction in the lymph node in response to anti-BR3 treatment appeared greater than that resulting from anti-CD20 mAb treatment (B). B-cell subsets were quantified using similar definitions as in Figure 1. Spleen and bone marrow plasma cells were defined as CD138⁺B220^lo/−. Analysis of different B-cell subsets after 8 weeks of continuous treatment (200 μg/week anti-BR3 and anti-CD20; 150 μg × 3/week BR3-Fc) shows significantly higher MZ B-cell, spleen, and BM plasma cell reduction in anti-BR3 mAb compared with anti-CD20 mAb treatment (C). Serum IgM and IgG1 were measured by ELISA after 3 months of continuous treatment (D). These data are representative of 3 independent experiments. Data are shown as mean plus or minus standard error. Statistical significance compared with the control treated group is indicated with an asterisk. When 2 treatment groups are significantly different from each other, the P value is displayed.