CXCL12 and B-cell chronic lymphocytic leukemia: Although it was expected that the CLL cells would have the stronger migratory response due to higher CXCR4 expression, these results are consistent with previously published observations that showed weak migration of CLL cells to CXCL12 compared to a much more robust response to the CCR7 ligands, CCL19 and CCL21 [14], [15].