Indeed, we found that recently divided cells (“proliferative fraction”), identified by a CXCR4DimCD5Bright (165) or CLL cells undergoing CSR to IgG (IgM+/IgG+ phenotype) (161), were the only circulating leukemic cells that expressed AID (88, 145, 161). Here, AICDA is linked to B-cell chronic lymphocytic leukemia.