We used deuterium incorporation into newly synthesized DNA in leukemic cells from patients with CLL to refine the “aging” kinetics, characterizing additional fractions differing in surface membrane (sm) CXCR4/CD5 levels, i.e., CXCR4DimCD5Dim double dim fraction (DDF) and CXCR4BrightCD5Bright double bright fraction (DBF); and fractions differing in (sm)IgM and IgD densities. Here, CXCR4 is linked to B-cell chronic lymphocytic leukemia.