The means of analyzing and isolating Tregs in cancer patients naturally followed the “evolutionary path” of their progressing phenotypic characterization [21]; soon after CD4+CD25high lymphocytes were convincingly shown to grossly represent the suppressive population in healthy individuals [8] it could be demonstrated that such cells were infiltrating tumor tissue and circulated at increased proportions in patients with lung and ovarian cancer [22]. This evidence concerns the gene CD4 and neoplasm.