Splenomegaly and leukemic T-cell overgrowth in infected IBMI-huNOG mice. (A) Hepatosplenomegaly in HTLV-1–infected mice. Representative spleens and livers from mock- and HTLV-1–infected mice are shown. Scale bars in panel A represent 10 mm. (B) PVL in lymphoid organs of HTLV-1–infected mice. PVL in the peripheral blood (PB), spleen (SP), bone marrow (BM), and lymph nodes (LM) of HTLV-1–infected mice (n = 17) are shown. Box plots represent medians ± 1.5 IQR. Asterisks indicate statistical significance vs the value obtained from peripheral blood (*P < .05, ***P < .001 by paired t test). (C) Downregulation of CD3 on the T-cell surface. PBMCs from mock- (n = 3) and HTLV-1–infected mice (n = 18) were stained for human CD3 and analyzed by FACS. Results are presented as mean MFI ± SD of CD3 expression. (D-E) Smears of peripheral blood from HTLV-1–infected mice showing a number of leukemic cells with atypically shaped nuclei. Results from two infected mice (7 and 18 wpi, respectively) and a mock-infected mouse (at 8 mpt) are shown. Higher-magnification view of flower cells in panel D is shown in panel E. Scale bars in panels D-E represent 50 and 10 µm, respectively. Asterisks in panels B and C represent significant differences vs mock-infected mice (**P < .01 by Mann-Whitney U test).