Fig. S2.

B-cell subsets analysis by flow cytometry in a/b heterozygous mutant models. Freshly collected cells from 8- to 10-wk-old F1 mice (expressing IgH alleles of a and b allotypes) of each genotype (wt ^a/^b, 3′PAL^Δa/^wtb, hs3b-4^Δa/^wtb, and 3′RR^Δa/^wtb) were stained with fluorescent antibodies and analyzed by FACS. For Bone marrow B220⁺-gated cells, IgM^a- and IgM^b-expressing cells were separated: percentages of B220^int/IgM⁺ NF/immature B cells and B220^high/IgM⁺ mature recirculating (MR) B cells are indicated. Splenic populations: dot plots show percentage of AA4.1⁺-gated transitional B cells expressing intracellular IgM^a or IgM^b allotypes; percentage of cells expressing intracellular IgM^a or IgM^b allotypes in MZ B cells (gated on CD19⁺ B220⁺ CD21^high CD23^low) and FO B cells (gated on CD19⁺ B220⁺ CD21^low CD23^high). For B220⁺-gated peritoneal cavity B-lineage cells, IgM^a- and IgM^b-expressing cells were separated: percentage of CD5⁻/IgM⁺ B1b B cells and CD5⁺/IgM⁺ B1a B cells are indicated.