Diminished follicular B cells in mb.1-Rap1A17 Tg mice. (A) Spleen cells from Rap1A17^f and mb.1-Rap1A17 Tg littermates were multicolor analyzed with the indicated antibodies with the use of FACSCalibur (left). The mean numbers and SEs of T1 (B220⁺ CD21^low CD23⁻), MZ (B220⁺ CD21^high CD23⁻), and FO (B220⁺ CD21^low CD23⁺) B cells in the spleens of Rap1A17^f (□) and mb.1-Rap1A17 (■) Tg littermates (5 mice each) are indicated (middle). Peripheral blood cells were also analyzed with the indicated antibodies (right). (B) Peritoneal exudate cells from Rap1A17^f (□) and mb.1-Rap1A17 (■) Tg mice were 2-color analyzed with the indicated antibodies (left), and the numbers of B1 (B220⁺ Mac1⁻), B1a (B220⁺ CD5⁺), and B2 (B220⁺ Mac1⁻ CD5⁻) cells, as well as macrophages and T cells, are indicated (right). The means and SEs of 5 mice in each group are shown. (C) Indicated B-cell subsets sorted from the spleen and peritoneal cells from mb.1-Rap1A17 Tg mice were assessed for Cre-mediated recombination by genomic PCR. (D) The spleens from mb.1-Rap1A17 (■) and Rap1A17^f (□) littermates were immunostained with the indicated antibodies (Cy3-anti–CD3 and Alexa Fluor 488 anti-B220). indicates MZ, and bars indicate 400 μm (top) and 100 μm (bottom). The mean follicular numbers in 4 sections of central regions and the mean major axis (in μm) of 60 follicles were measured.