CD4 and neoplasm: If tumor implantation can be attributed to resistance to NK cell cytotoxicity, tumor remission could then be attributed to the increase in the percentages of CD8+ and granzyme+ cells in the case of cRb−/−/RasV12 tumor, and to the increase in the percentages of CD8+CD69+, CD4+CD69+ and granzyme+ cells, and to the decrease in the percentage of regulatory CD4+CD25+ cells in the case of RasV12 tumor.