Considering that TCL1-Tg BAFF-/- mice were protected against CLL in comparison to TCL1-Tg mice, we hypothesized that peritoneal CLL cells from TCL1-Tg mice may have a transcriptomic signature reflecting the aggressiveness of these cells, and that this signature should be attenuated in CLL cells from TCL1-Tg BAFF-/- mice sequestered in the peritoneal cavity. This evidence concerns the gene TNFSF13B and B-cell chronic lymphocytic leukemia.