Expression of Foxp3EGFP in T cells from tumor-bearing and control mice. Splenocytes (SPL), lymph node lymphocytes (LN), and tumor-infiltrating lymphocytes (TIL) were isolated from control and B16 tumor-bearing C57BL/6 Foxp3 EGFP mice and analyzed by flow cytometry for Foxp3EGFP expression in CD8 and CD4 lymphocytes. B16 (boxes) or B16-OVA (open triangles) tumors were allowed to grow to 7-10 mm in diameter at which point they either did (closed boxes) or did not receive daily intraperitoneal injections of 50,000 units IL-2 for three days prior to analysis on the following day. Foxp3EGFP expression in CD8 T cells from control and tumor-bearing mice were at equivalently low percentages. The percent of CD4 cells that expressed Foxp3EGFP in SPL (p = 0.002) and TIL (p = 0.001) was significantly elevated in tumor-bearing mice compared with non-tumor-bearing controls. Statistical analysis and P-value determinations were done by two-tailed Welch's T-test for determination of the significance of differences between the groups of continuous variables. P < 0.05 was considered to be statistically significant. Graphs were constructed using GraphPad Prism 4.0 software and statistical functions were analyzed using Micorsoft Excel.