Incubation of CLL cells with IL-4 + CD40L significantly reduced NKG2A+, but not NKG2A-, NK cell activation against CLL cells as measured by IFNγ production (mean 5.2–3.8%, P < 0.01) and degranulation (mean 18.7–15.9%, P < 0.001) (Fig. 7F–H), consistent with NKG2A acting as an inhibitory immune checkpoint [46]. Here, IL4 is linked to B-cell chronic lymphocytic leukemia.