The differential effect of B-cell depletion by 2 subclasses mouse anti–mouse CD20 monoclonal antibodies. E16 mice (n = 3 or 4) were intravenously injected with 250 μg of either IgG1 or IgG2a anti-CD20, or the same dose of control mouse IgG1 + IgG2a. Two weeks after the antibody treatment, the extent of B-cell depletion was evaluated using the splenic cells by cell counting and fluorescence-activated cell sorter analysis of B-cell surface markers. (A) The representative bar graphs for the percentage of B cells (CD19⁺). (B) The representative dot plots for the percentage of MZ B cells (CD23^intCD21^hi) and FO B cells (CD23^hiCD21^low) after gating on CD19⁺ cells. (C) The absolute numbers of total B cells (left panel), marginal zone B cells (middle panel), and follicular B cells (right panel). Data are mean ± SEM. Representative data from more than 3 independent experiments with similar results.