XCL1 and B-cell chronic lymphocytic leukemia: Although some publications show an increased in vitro survival of CLL cells by rhA when used at a concentration of 500 ng/ml,4,12 our experiments using 200 ng/ml rhA (Figure 2e) are in line with the data of several other groups that were unable to find effects of recombinant APRIL, either alone22 or in combination with B-cell activating factor and chemokine (C-X-C motif) ligand 1 (CXCL)12.23 Also, we established that the amount of APRIL produced by macrophages is >100 orders of magnitude lower compared with concentrations used in the reports that detect survival by APRIL.