CD4 and B-cell chronic lymphocytic leukemia: In summary, our studies have demonstrated that the levels of IL-17F-expressing CD4+ T cells are significantly higher in CLL versus healthy PBMCs following in vitro stimulation in the presence of Th17-promoting cytokines and that both leukemic B cells and CLL T cells are responsive to IL-17F-mediated signaling, specifically activating NFkB.