CXCR4 and B-cell chronic lymphocytic leukemia: Since the proportion of CXCR3-CXCR4 heteromers is relative to homomers of both receptors [28], low levels of CXCR3 on CLL cells, observed in our patients with mutated IgHV status, might not be sufficient to abrogate migration of CLL cells driven by CXCR4.