(A) Leukemic CLL B cells express higher levels of CXCR4 than the T cells from CLL B patients. The average MFIR of CLL B cells (n = 12; shaded) was significantly higher than the mean CXCR4-MFIR of T cells (n = 12; hatched). The dots represent CXCR4-MFIR values for CLL B and T cells from individual patients, with lines connecting the values from the same patient sample. (B) SDF-1 induces CXCR4 receptor downmodulation on CLL B cells and T cells. Using anti-CXCR4 along with anti-CD19 and anti-CD3 MoAbs, we determined the CXCR4 MFIR values for CLL B cells (shaded boxes) and T cells from the same CLL patients (hatched boxes) after preincubation with 1, 10, 100, 1,000, or 2,500 ng/mL SDF-1 or medium alone. The data represent the MFIR values (±SD) from 3 different patient samples.