Therefore, it is of considerable interest that although the levels of IL-17F-expressing CD4+ T cells are higher in CLL versus healthy PBMCs following in vitro stimulation for 7 days in the presence of Th17-promoting cytokines, the percent of IL-17A-expressing CD4+ T cells are not (data not shown). This evidence concerns the gene CD4 and B-cell chronic lymphocytic leukemia.