G_αq-deficient B cells have a competitive survival advantage over WT B cells in vivo. (A–C) Splenic B cells were purified from WT and Gnaq^−/− chimeras (CD45.2⁺) and transferred i.v. into CD45.1⁺ WT hosts (2.5 × 10⁷ cells/host). (B) Spleen cells from recipient mice were harvested at 1–3 wk after transfer and analyzed by flow cytometry to identify donor B cells. Representative dot plots and the mean percentage ± SD of cells of donor origin are shown. (C) The number of donor B cells recovered per recipient spleen was determined and is shown as the mean ± SD (n = 3–5 mice/group/time point). Data are representative of two independent experiments. (D–G) Lethally irradiated CD45.1⁺ WT mice were reconstituted with a mixture of BM consisting of 50% Gnaq^−/− (CD45.2⁺) BM and 50% WT (CD45.1⁺) BM. (E) Splenic B cells were collected from the 50:50 BM chimeras and flow cytometry was used to identify WT and Gnaq^−/− B cells. Data are presented as the ratio of Gnaq^−/− to WT B cells (percentage of Gnaq^−/− B cells divided by percentage of WT B cells) at each time point and are shown as the mean ± SD from five mice per group. Data are representative of more than three independent experiments. (F) BM and spleen were collected from the 50:50 BM chimeras at 2 mo after reconstitution, and the ratio of Gnaq^−/− to WT B cells was determined as described in E. Splenic B cells were subdivided into total mature (B220⁺CD93⁻), FOB (B220⁺CD21^loCD23^hi), MZB (B220⁺CD21^hiCD23^lo), T1 (B220⁺CD93⁺CD23⁻), T2/T3 (B220⁺CD93⁺CD23⁺), T1 MZB precursors (B220⁺CD93⁺IgM^hiCD21^hi), and T2/FOII MZB precursors (B220⁺CD93⁻CD21^hiCD23^hi). B cells in the BM were subdivided into immature (fraction E) B cells (B220⁺CD93⁺IgM⁺), transitional (B220⁺CD93⁺IgM^hiCD23⁺), and recirculating (B220^hiIgM⁺IgD⁺). Data are shown as the mean ± SD of four to five mice/group. (G) 50:50 BM chimeras (2 mo after reconstitution) were injected with EdU twice over a 12-h period. Spleen cells were isolated at 18 h, stained with Abs to CD19 and CD45.2 and the EdU detection reagent, and then analyzed by flow cytometry. Representative FACS plots are shown and the percentage of B cells of each genotype that incorporated EdU is provided. Data shown are the mean ± SD of five mice. Data in D–G are representative of two independent experiments.