Splenomegaly and extramedullary hematopoiesis in Tc1 mice older than 15 months. (A) Photograph shows appearance of an enlarged spleen found in a Tc1 mouse aged 15 months, alongside a spleen from a wild-type (Wt) age-matched control mouse. Size marker indicates 1 cm. (B) Graph shows weights of spleens taken from mice aged 15 months or older. Horizontal bar indicates the mean. (C) Graphs showing mean (± SEM) total number of cells in the spleen and bone marrow of mice of the indicated genotypes and ages (n = 6-11). (D) Graphs showing mean (± SEM) number of megakaryocytes per microscope field (40× objective) in mice aged older than 15 months (n = 5). (E) Histograms of flow cytometric analysis of surface levels of Ter119 expression on spleen and bone marrow cells from a Wt mouse at 2 months of age. Numbers indicate percentage of cells falling into the indicated markers. Graphs show mean (± SEM) numbers of Ter119⁺ cells in the spleens and bone marrow of mice of the indicated ages and genotypes (2 months, n = 11 [Wt], n = 10 [Tc1]; > 15 months, n = 7 [Wt], n = 11 [Tc1]). *P < .05, **P < .01.