TNFSF13B and B-cell chronic lymphocytic leukemia: CLL cell survival is promoted by tumor-associated macrophages known as nurse-like cells through the secretion of a proliferation-inducing ligand (APRIL), a B-cell activating factor (BAFF), the C-X-C motif chemokine CXCL12 (also known as stromal cell-derived factor 1 (SDF-1)), and soluble CD14 or the lymphocyte function-associated antigen 3 (LFA-3)/CD2 interaction [12].