Characterization of the REL-AID mouse model. (A) Schematic representation of the REL-IRES-YFP and tdTomato inserts into the Rosa26 locus: the REL sequence was placed in frame with the IRES and the coding sequence for YFP. On the same chromosome 6 bearing tdTomato trangene, Cre_ert2 was inserted into Aicda locus. (B) Schematic diagram of SRBC (red arrow) and tamoxifen (black arrow) administration protocol for mouse analysis (green arrow) at different time points after immunizations. Blood samples were collected on D14 and then each month, always before immunization boost (blue arrow). (C) Example of a flow cytometry biparametric YFP and tdTomato (TOM) histogram gated on live B220pos B cells. TOM⁺/YFP^– and TOM⁺/YFP⁺ B cells are colored in red and green, respectively. PB cells were collected from an AID-TOM (left) or a REL-AID (right) mouse 14 day after immunization and tamoxifen gavage. Percentages of fluorescent cells are shown in each graph. (D) Relationship between the percentage of TOM⁺/YFP⁺ among total TOM⁺ B cells (x-axis) and that of TOM⁺ B cells among total B220⁺ B cells (y-axis) in REL-AID mice on D14. The correlation curve is shown in red. The value of the Pearson correlation coefficient r with its P value is shown in the graph. Each experiment has been done at least 4 times.