We30 and others3 have previously found that monocyte-derived cells such as macrophages are able to induce survival of CLL cells, and it was suggested that survival by monocyte-derived cells is dependent on APRIL.12 Although we did not observe a survival effect of stimulation with APRIL as a single stimulus (Figure 2e), the effects of APRIL could be dependent on other macrophage-expressed cytokines. This evidence concerns the gene TNFSF13 and B-cell chronic lymphocytic leukemia.