BCR and B-cell chronic lymphocytic leukemia: The survival signals to CLL cells include, but are not limited to, the expression of CXCL12 [104], CD31, plexin B [112], a proliferation-inducing ligand (APRIL), B-cell-activating factor (BAFF), [113], BCR stimulation [114] and CD2 expression [115] by NLCs.