Expansion of CD4⁺/CD8⁺ cells in the peripheral blood of FW-pX rats. The top and bottom panels show the results of FCM analyses of peripheral blood from 6-week-old FW-wt (F1 generation of wild-type F344 and Wistar) and FW-pX (F1 generation of HTLV-I pX transgenic F344 and wild-type Wistar) rats, respectively. Peripheral blood cells were stained with FITC-conjugated anti-CD3 (G4.18), FITC- or PE-conjugated anti-CD4 (OX-35), and PE-conjugated anti-CD8 (OX-8) Abs, followed by depletion of erythrocytes. At first, the cells were divided based on the forward (FSC) and side scatter (SSC) patterns. Then, PBMCs in region 1 (R1) were gated to analyze the expression of CD3, CD4, and CD8. In both groups, at least 3 rats were examined. Representative data are shown. The numbers in each panel represent the percentage of CD4⁺ T cells, CD8⁺ T cells, and CD4⁺/CD8⁺ cells, respectively.