Impact of B-cell depletion in the spleen of AID-Cre-EYFP mice. AID-Cre-EYFP mice were immunized by 2 SRBCs injections 1 month apart, together with a tamoxifen regimen, and were injected with (n = 14) or without (n = 12) anti-CD20 antibody (3 × 250 µg, IV) (see supplemental Figure 2B). Analysis originates from ≥2 independent tamoxifen-labeling experiments. (A) Kinetics of B-cell depletion in mouse blood (D0 represents the first day of anti-CD20 antibody injection). (B) Comparison of EYFP⁺B220⁺ B-cell numbers in spleens of control mice (3 months after immunization) and anti-CD20–treated mice at the nadir of B-cell depletion (day 50 after first anti-CD20 injection). (C) Comparison of EYFP⁺B220⁻ PC numbers per spleen in controls and anti-CD20–treated mice at day 50 after the first anti-CD20 antibody injection. (D) Comparison of IgG1⁺, IgA⁺, and IgM⁺ splenic EYFP⁺B220⁻ PC numbers in controls (n = 4) and anti-CD20–treated (n = 4) mice at day 50 after the first anti-CD20 injection, determined by intracellular staining. Anti-CD20–treated and control mice showed a 2.5-fold difference in the number of IgG1⁺ cells (P < .01). Significant differences were estimated by the Mann-Whitney U test (****P < .001). Mean values are indicated.