Leukemia development in Eμ-TCL1/IgSm transgenic mice. (A) Plots depict the percentage and absolute number of IgMa⁺ (filled circles) and IgMa⁻ (empty circles) B cells in the peripheral blood of Eμ-TCL1/IgSm transgenic mice (n = 12) at the indicated time points. One mouse died of leukemia at 11 months of age. (B) Flow cytometry analysis of surface IgMa and IgMb expression in representative leukemias. Analysis was performed on CD19⁺ cells. (C) Flow cytometry analysis of leukemic cells stained with biotinylated Sm and anti-IgMa. Analysis was performed on the lymphocyte gate.