While CD4+/CD8- cells did not regenerate when CD4+ cells were depleted prior to implantation, there was a striking increase of CD8+/CD4+ double-positive cells in spleen (32.7%) and tumor (27.4%) as compared to animals that received whole PBL where these double-positive cells only represented 8.2% and 9.9%, respectively. This evidence concerns the gene CD4 and neoplasm.