Igκ-LPETG mice have near normal B-cell development. (A–C) Serum immunoglobulins from the indicated mice were analyzed by ELISA. All mice analyzed are shown. Unpaired Student’s t test was performed to compare the ratio of serum Igκ to Igλ antibodies and antibody concentrations. (D) Splenic B cells were labeled for surface markers and gated on AAD^-CD19⁺Igκ⁺Igλ^- or AAD^-CD19⁺Igκ^-Igλ⁺ and their ratio plotted. The graph shows all mice analyzed. One-way ANOVA was performed to compare the ratio of Igκ and Igλ splenic B cells in the indicated mice. (E) Representative plots of experiment shown in (D). (F) Igκ-LPETG^+/+ splenic B cells were isolated and labeled for Igκ and Igλ with spectrally divergent dyes and visualized by imaging flow cytometry. (G) Populations within the B-cell compartment were identified as described by flow cytometry.¹⁶ Bone marrow: Pro-B cells (AAD^-B220⁺CD43^highCD19^low), Pre-B cells (AAD^-B220⁺CD43^int.CD19^int.), and Immature B cells (AAD^-B220⁺CD43^lowCD19^high). Spleen: Transitional B cells (AAD^-CD19⁺CD21^low/-CD23^-), Marginal zone B cells (AAD^-CD19⁺CD21⁺CD23^low/-), and Follicular B cells (AAD^-CD19⁺CD21^intCD23^int). The graphs shown here include all mice analyzed. (A–D) N.S.: P > 0.05; *P ≤ 0.05; **P ≤ 0.01; ***P ≤ 0.001; ****P ≤ 0.0001. All graphs show the mean ± SD.