CXCL12 and B-cell chronic lymphocytic leukemia: Similar to the CXCR4/CXCL12 axis, the CXCR5/CXCL13 axis also plays a role in CLL homing and trafficking, since CXCR5 is overexpressed on the CLL B cell surface and CXCL13 is secreted by stromal cells in B cell areas of secondary lymphoid tissues (112): FDCs produce CXCL13 which directs B lymphocytes to the “light zone” of the germinal center (5).