Figure. Concentration-dependent activation of CCR5 by CCL4. Reporter cells were transfected with either the expression plasmid for C-C motif chemo­kine receptor 5 (CCR5) or the mock plasmid and treated with various concentrations of C-C motif chemo­kine ligand 4 (CCL4). Data points shown are the mean ± SEM of an experiment performed in triplicate, and the curve is a fit to Hill equation with an EC50 of 7.1 nM.