Flow cytometric analysis of the B-cell differentiation stage in TPM3-ALK double-transgenic mice. Representative dot plots of flow cytometric analysis of lymph node cells prepared from 4-week-old control tTA littermate and TPM3-ALK (tTA/pBIL-TA) double-transgenic mice. CD19 versus CD3 profiles of live gated lymphocytes are shown (A). ALK or isotype control (Iso Cont) versus membrane CD19 FACS profiles are shown (B-C). Lymph node cells were labeled with anti-CD19 and with anti-ALK antibodies and with anti-CD43 (D), anti-μ heavy chain (E), anti-immunoglobulin M (IgM; F), anti–pre-B cell receptor (BCR; G), and CD25 (H) antibodies. ALK-positive cells are plotted in red (C-H). Vertical and horizontal cursors were set so that > 99% of events in control unstained samples were in the bottom left quadrants. The numbers indicate the median percentage of cells with SD in a quadrant, relative to the plots of tTA and tTA/pBIL-TA transgenic mice.