Characterization of the Cγ1-CDE strain. (A) Targeting strategy for the insertion of the IRES-Cre_T2A_DreERT2 cassette into the 3′-UTR downstream of the last membrane exon of the mouse Cγ1 locus. (B–J) Experimental scheme using the Cγ1-CDE, R26-BFP^stopF, R26-ZsGreen^stopRox compound mutant mice, immunizing with NP-CGG at day (d)0, administrating TAM at day 2–5 (B), 9–12 (C), or 15–18 (D) and analyzing at day 7, 14, or 21, respectively. (B–D) Percentage of Cre-mediated BFP⁺ (left panel) and Dre-recombined ZsGreen⁺ (within the BFP⁺) cells (middle panel) among splenic Fas⁺CD38⁻ GCBCs, splenic class-switched Fas⁻CD38⁺IgD⁻IgG1⁺ MBCs, and CD138⁺TACI⁺ PCs from spleen and bone marrow (BM) (from one femur and tibia), as well as corresponding absolute numbers of the BFP⁺ZsGreen⁺ cells (right panel). (E–G) Percentage of Fas⁺CD38⁻ GCBCs at day 7 (E), day 14 (F), and day 21 (G) after NP-CGG immunization. (H–J) Percentage of ZsGreen⁺ (within BFP⁺) CXCR4^hiDC86^low DZ and CXCR4^lowCD86^hi LZ GCBCs at day 7 (H), day 14 (I), and day 21 (J) after NP-CGG immunization. Data points for GCBCs without TAM administration are compiled from the three time points analyzed. Statistics: Mann–Whitney test, *P ≤ 0.05; **P ≤ 0.01; ***P ≤ 0.001; ****P ≤ 0.0001; ns, not significant. Each dot represents one mouse. Data are from at least two independent experiments. Horizontal lines indicate the median.