Figure 4.

BAFFR deletion results in the loss of MBCs. (A) Mixed bone marrow chimeras were generated by reconstituting irradiated Rag1^−/− mice with 10% bone marrow from Baffr^+/+RCE or Baffr^fl/flRCE (CD45.1⁻CD45.2⁺) and 90% WT bone marrow (CD45.1⁺CD45.2⁺) for 41 d. Mice were immunized with NP-CGG in alum or alum alone on day 0 and boosted with NP-CGG in PBS or PBS alone 17 d later. Mice were injected with anti-CD40L on days 33, 35, and 37, followed by five daily tamoxifen injections. (B) Flow cytometric analysis of splenocytes from mice immunized with NP-CGG in alum treated as described in A and analyzed on day 66, showing gating strategy for CD45.1⁻CD45.2⁺ total naive B cells (B220⁺CD138⁻Fas⁻PD-L2⁻) and for NP⁻ IgG1⁺ MBCs and NP⁺ IgM⁺ and IgG1⁺ MBCs (B220⁺CD138⁻Fas⁻PD-L2⁺). Numbers in dot plots indicate percentages of cell populations within gates (red boxes). (C) Mean (±SEM) numbers of total naive B cells and of NP⁻ IgG1⁺ and NP⁺ IgM⁺ and IgG1⁺ MBCs in spleens of mice immunized with NP-CGG in alum (+; n = 14 for Baffr^+/+RCE and n = 11 for Baffr^fl/flRCE) or alum alone (−; n = 4). Each dot represents one mouse. Data pooled from two independent experiments. Mann-Whitney test was used for statistical analysis. *, 0.01 < P < 0.05; **, 0.001 < P < 0.01; ***, 0.0001 < P < 0.001; ****, P < 0.0001.