The levels of CD4+CD25+ cells in PEF2 and PEF2 + Ca-treated mice were lower than in tumor-bearing controls, but higher than in tumor- free mice (average of 4% in tumor-free mice, 6.9% in tumor-bearing mice and around 4% in PEF2 and PEF2 + Ca-treated mice). This evidence concerns the gene CD4 and neoplasm.