Figure 2. Reduced CSR in the absence of TRRAP. (A) CD43⁻ sorted splenic B cells with the indicated genotypes were induced to switch to IgG1 with LPS+IL4. At day 4 post-stimulation, the cells were stained with anti-B220-APC and anti-IgG1-FITC (top). The statistical data are shown in the bottom panel (n = 7). (B) The levels of GL and Aicda transcripts were estimated by semi-quantitative RT-PCR. Total RNA was prepared at day 2 from LPS+IL4-activated B cells and reverse transcribed. Five-fold serial dilutions of single-strand cDNAs were amplified by using appropriate primers. Actin transcripts were used for normalization (n = 5). (C) Resting B cells were induced to switch for 3 d and stained with anti-IgG1-FITC. The IgG1⁺ fraction was sorted and analyzed as described in Figure 1B. The histograms show the percentage of deleted alleles among 95 positive wells. The IgG1⁻ fraction was sorted and analyzed as described in Figure 1B. The histograms show the percentage of deleted alleles among 46 positive wells.