To interrogate the phenotypes of quiescent and proliferating CLL cells further, we overlayed the G0, G1, and S/G2/M fractions revealing distinct CXCR4 and CD5 expression profiles (Figure 1D) with lowest levels of CXCR4 on cells in G1 in U‐CLL and highest CXCR4 expression levels on cells in S/G2/M for both U‐CLL and M‐CLL (Figure 1E). Here, CXCR4 is linked to B-cell chronic lymphocytic leukemia.