D6 increased its membrane expression and scavenging rate upon ligand stimulation. (A-C) CHO-K1/D6 cells were incubated at 37°C with (A) 100 nM of the indicated chemokine for 30 minutes, (B) increasing concentrations of CCL3L1 for 60 minutes, (C) medium (□) or 100 nM CCL3L1 (■) for the indicated times. D6 membrane expression was analyzed by flow cytometry and data were expressed as percentage of MFI over untreated cells. Results (means ± SEM) were from at least 3 independent experiments performed. Asterisks indicate significant differences of cells incubated with indicated chemokine versus untreated cells (*P < .05; **P < .01). (D) JAR (●) and CHO-K1 cells transiently transfected with CCR5-pEGFP (□) or D6-pEGFP (■) were sorted and then incubated at 37°C with 0.1 nM ¹²⁵I-CCL4 and 1 to 300 nM CCL4. Data were analyzed as described in “Chemokine scavenging assay.” Results (means ± SEM) shown in panels A-C are from at least 3 different experiments performed, and asterisks indicate significant differences between medium and treated cells; results (means ± SEM) in panel D are from triplicates of 1 representative experiment of 3 performed. Asterisks indicate significant differences between JAR- and CHO-K1/D6- versus CHO-K1/CCR5-transfected cells (*P < .05; **P < .01).