Figure 4. Active SHM in BM Immature B cells and Persistence of Somatic Variants in the Spleen of Naïve Mice.

BM immature B cells (AA4.1⁺B220⁺κ⁺λ⁺), splenic transitional B cells (AA4.1⁺IgM^hiIgD⁺), and follicular B cells (AA4.1⁻IgM^loIgD^hi) were sorted as shown in Figure 3. Rearranged Vκ4-Jκ5 light chain DNA was amplified with a specific primer set (Figure 3A), cloned and sequenced. (A) The sequencing results are depicted as pie charts as described above. Each P value was obtained by two-tailed Student's t-test. (B) Mutation frequencies were calculated by the number of nt change per 10⁴ bp from C57BL/6 (filled bars) and from Aicda^−/− (open bars) mice.