Loss of p53 does not rescue class switch recombination defects observed in <i>Rnf8^−/−</i> mice.

<p>(A) B-cells were purified from the spleen of 6-week old <i>Rnf8^−/−p53^−/−</i> and control mice and class switch recombination was examined. B-cells were treated with anti-CD40 and IL-4 for 4 days, then the percentage of B-cells that have switched to IgG1 expression was determined by flow cytometry. Data presented are representative of at least 4 different experiments. (B) Quantification of Ig switching to IgG1. Percentage of B-cells that were IgG1⁺ after 4 days of stimulation <i>in vitro</i> in the presence of anti-CD40 and IL-4. Data are presented as the means SD of at least 4 independent experiments. * represents statistical significance (P<0.05) using a student t-test. (C) Cell division profiles of <i>Rnf8^−/−p53^−/−</i> B-cells and their controls. Cells were stained with CFSE and allowed to proliferate for 4 days in the presence of CD40 and Il-4. CFSE dilution profiles were examined using flow cytometry.