BCR and B-cell chronic lymphocytic leukemia: Moreover, NLCs are blood monocyte-derived cells that secret CXCL12 and 13, and that protect CLL cells from spontaneous apoptosis or drug-induced apoptosis in response to CXCL12, B cell-activating factor (BAFF), a proliferation-inducing ligand (APRIL), CD31, plexin-B1, and activation of the BCR signaling cascade (69–72).