B cell subsets and sIg expression in Igh^CGG/+ mice. (a) Splenocytes from 6-wk-old Igh^CGG/+ or WT C57BL6 mice were stained as indicated. For Igh^CGG/+ mice, CD19⁺ cells were analyzed separately as either CGG binding or nonbinding, the latter representing B cells that escaped the transgene. B cells were classified as Fo (CD93⁻ CD23⁺ CD21^lo IgM⁺), MZ (CD93⁻ CD23⁻ CD21^hi IgM^hi), and B1 (CD93⁻ CD23⁻ CD21^int IgM^int). WT mice were analyzed identically on the total CD19⁺ population. Error bars are SD of biological replicates. (b) Summary of splenic data as in panel a for four mice of each genotype. MZ, B1, and Fo B cells are shown as percentage of all IgM⁺ cells for WT mice or as percentage of IgM⁺ cells of that class (CGG binding or nonbinding) Igh^CGG/+ mice. *, P = 0.039 (unpaired t test). Fo B cells were also analyzed in skin-draining LNs (center), and splenic B cell subsets are also shown as absolute numbers (right). (c) B1b, B1a, and B2 B cell subset distribution in the peritoneal cavity of Igh^CGG/+ and WT mice. Representative dot plots of B2 (B220+ CD11b⁻), B1a (B220⁺ CD11b⁺ CD5⁺) and B1b (B220+ CD11b+ CD5⁻) from the CGG-binding and nonbinding population of Igh^CGG/+ and WT mice. Bar graphs show summarized subset distribution of the B2, B1a, and B1b B cells from n = 3 Igh^CGG/+ and n =2 WT mice from two independent experiments. *, P ≤ 0.05; **, P ≤ 0.01; ***, P ≤ 0.001 (unpaired t test). Numbers within flow plots indicate percentage of cells in the designated gate.