CXCL13 and B-cell chronic lymphocytic leukemia: CLL B cells could interact with stromal cells via different receptor/ligand couples including ICAM-1/LFA-1 (74), VCAM-1/VLA-4 (75–78), CXCR5/CXCL13 (79), BCMA/BAFF, or TACI/BAFF (80), or by transpresentation of IL-15 from stromal cells to B cells (81).