Figure 3. NFκB activation in response to transient Rag DSBs.

(a) Flow cytometric analyses of CD40, CD69 and CD62L expression by B220⁺:IgM⁻ bone marrow B cells (gated cells in dot plot) from WT and Atm^−/− mice. Histograms for the specific antibodies (red) and isotype control (blue) are shown. (b) Flow cytometric analysis of GFP expression in Rag2^−/−:NRE and Rag2^−/−:NRE:R2 cells treated with STI571 for 48 hours in the presence or absence of the Atm inhibitor KU-55933 (iAtm). The percentage of GFP⁺ cells is indicated. Results are representative of three experiments. (c) Rag2^−/− :NRE and Rag2^−/−:NRE:R2 abl pre-B cells were un-treated (−) or treated with STI571 for 48 hours (+) and GFP⁺ and GFP⁻ Rag2^−/−:NRE:R2 abl pre-B cells isolated by flow cytometric cell sorting. Serial 4-fold dilutions of genomic DNA from all cells was assayed for pMX-DEL^CJ rearrangement by PCR (see Supplementary Fig. 15b). Results are representative of two experiments. (f) Flow cytometric analysis of CD40 and CD69 protein expression on GFP⁺ (blue histograms) and GFP⁻ (red histograms) Rag-2^−/− :NRE:R2 cells treated with STI571 for 24 or 72 hours. Results are representative of two experiments.