By contrast, whereas healthy peripheral blood B cells produced IL-10 following stimulation with 4 μg/ml CpG, they failed to respond to CXCL12, pointing to a unique role for the CXCL12–CXCR4 axis in mediating IL-10 response in CLL cells (Figure S4C in Supplementary Material). The gene discussed is CXCR4; the disease is B-cell chronic lymphocytic leukemia.