Figure. Concentration-dependent activation of CCR4 by CCL22. Reporter cells were transfected with either the expression plasmid for C-C motif chemo­kine receptor 4 (CCR4) or the mock plasmid and treated with various concentrations of C-C motif chemo­kine ligand 22 (CCL22). 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 20 nM.