CXCL12 and B-cell chronic lymphocytic leukemia: B-cell positioning in these areas is coordinated by the chemokines CXCL12 and CXL13, which are expressed by stromal cells,49 and CXCR4 and CXCR5, which are differentially expressed by the B cells.50 In addition, bone marrow and LN stromal cells secrete CXCL9,10,11,12,13 and CCL19 and 21 which bind CXCR3, CXCR4 and CXCR5 receptors different expressed by the leukemic clone.51 In turn, CLL B cells, also secrete chemokines such as CCL3, CCL4, CCL22 and interleukin-8, which can attract accessory cells, such as T cells and monocytes.