Figure 2

Efficiency of CCL19 induced chemotaxis of B-CLL cells is independent of the expression level of CCR7 but not of CRAM. A. The two upper panels depict CCR7 and CRAM expression at the surface of B cells from 4 patients with B-CLL (B-CLL1 to 4). Out of 23 patients tested, we selected two isolates of samples with similar levels of CCR7 and highly variable CRAM, and MEC-1 cells are shown as a reference. Results shown are MFI from a single flow cytometry experiment for the patients' samples; isotype control was repeated for each of them and represented as the mean of the 5 experiments + SD. The lowest panel depicts the mean + SD of chemotaxis toward 200 ng/ml CCL19 (one experiment done in triplicate). B. CCR7 and CRAM expression were tested at the surface of MEC-1 cells after migration induced by 200 ng/ml CCL19 or CCL21 and compared with the level of expression of cells before migration (control). A significantly lower CRAM expression is observed on cells that have migrated to CCL19 (unpaired T-test, p = 0.0007). The histograms below the graph depict one representative experiment, showing lowered CRAM expression in cells moving toward CCL19 (blue) but unaltered CRAM expression in similar experimental conditions with CCL21 (green). No alteration of CCR7 level of expression is observed (middle histogram). Incubation of MEC-1 cells with either CCL19 or CCL21 does not alter the detection of CRAM by the antibody used for the previous experiments (right histogram, one representative experiment).