Altogether, these findings suggest that the expansion of CD4+ CTL and/or Tαβ CD4+CD8lo cell populations may represent a regulatory mechanism to control tumor growth via direct tumor cell killing, which might explain why the lower numbers of those cells in CLL emerged here could be used as a surrogate marker of the dynamics of clonal CLL cells. This evidence concerns the gene CD4 and B-cell chronic lymphocytic leukemia.