Forced expression of c-Rel partially rescues B-cell defects in p85α^−/− mice. Recipient Rag-2^−/− mice on a BALB/c background were reconstituted with BM cells from p85α^−/− (−/−) or control (+/−) mice on a BALB/c background expressing either c-Rel (c-Rel), p85α (p85), or Venus alone (mock). Spleen cells were analyzed 10 weeks after transplantation. Among Venus⁺B220⁺ cells, the percentages of CD21^hiCD23^lo MZ B cells are shown (A). Among Venus⁺ cells, the percentages of IgM^loIgD^hi most mature B cells identified as the cells in the lower right quadrant are indicated (B). (C) Splenic B cells from p85α^−/− (p85α^−/−) or control (p85α^+/−) mice on a BALB/c background were unstimulated or stimulated with anti-IgM F(ab′)₂ (+ αIgM) and infected with lentivirus vector encoding c-Rel (c-Rel) or Venus alone (mock). Among Venus⁺ cells, BCR-induced cell-cycle progression was evaluated on a FACSAria using Hoechst 33342 as an indicator for DNA content. Shown are percentages of cells in S + G2/M. Mice are all on a BALB/c background. Data are representative of 3 (A,B) or 5 (C) independent experiments with similar results.