It is worth mentioning that, in those CLL patients who did not respond to lenalidomide, IL-2 was able to induce the proliferation and the cytotoxic activity of NK cells, suggesting that the level of induction of IL-2 production by CD4 T cells by lenalidomide may be involved in this marked variation of response. This evidence concerns the gene CD4 and B-cell chronic lymphocytic leukemia.