Fig. 1: Notch2IC drives conversion from a FoB toward a MZB surface phenotype.

a Representative FACS analysis of B220⁺ splenocytes from untreated N2IC/creER^T2hom and control mice. Numbers represent the percentages of CD23^lowCD21^high MZB and CD23⁺CD21⁺ FoB cells. n > 6. b Treatment scheme of N2IC/creER^T2hom mice to induce Notch2IC/hCD2-expression in FoB cells. c Percentages of hCD2⁺ splenic B lymphocytes at the indicated time points after tamoxifen treatment. *p = 0.0223, d3 n = 4, d7 n = 6, d14 n = 9, d30 n = 3. d Representative FACS analysis for CD23^lowCD21^high MZB cells at the indicated time points after tamoxifen administration. The plots are gated on B220⁺ lymphocytes (upper row) and in addition to hCD2⁻ (gray) and hCD2⁺ (blue) B cells (lower row). Indicated percentages refer to the gated populations within all B cells (black) and hCD2⁺ cells (blue). Plots are representative for repeated biological independent experiments per time point with d3 n = 4, d7 n = 6, d14 n = 9, d30 n = 3 animals. e The graph compiles the percentages of CD23^lowCD21^high MZB cells within hCD2⁺ cells at the indicated time points. ****p = 3.0E−05 (d3 vs d7), ****p = 1.6E−09 (d7 vs d14), *p = 0.0144. d3 n = 3, d7 n = 5, d14 n = 7, d30 n = 3. f Representative FACS analysis for the indicated MZB markers within hCD2⁺ and hCD2⁻ splenocytes from N2IC/creER^T2hom mice 30 days after tamoxifen treatment. MZB and FoB cells from control animals are shown in grayscales. n = 3. g, h Mice with the indicated genotypes were treated as shown in (b) and fed with BrdU via drinking water from day 1 to 7. FACS analysis for BrdU⁺ B cells was performed on day 7 after tamoxifen treatment (n = 3 for N2IC mice, n = 2 for CAR mice). g Percentages of BrdU/Ki67 double positive cells within reporter⁺ (hCD2⁺ or CAR⁺: blue) and reporter⁻ B220⁺ splenocytes (gray) from mice with the indicated genotypes. All BrdU⁺ cells were also positive for Ki67. *p = 0.0128. h Percentages of BrdU⁺ cells within splenic hCD2⁻ MZB (red) and hCD2⁻ FoB cell (gray) in comparison to hCD2⁺ cells (blue) from N2IC/creER^T2het mice. **p = 0.0034. g , h Same symbol shapes represent data from the same mouse within a genotype. For all bar graphs means, SDs and the values for each single mouse are indicated. c , e one-way ANOVA, Tukey’s multiple comparisons test; g,  h paired t-tests, two tailed.