U83A agonist and U83A-N antagonist for CCR5-mediated chemotaxis. (A) U83A induced chemotaxis on PBMCs, data shown are representative of 5 independent experiments, with maximum at 0.1 nM dose (P < .01, Dunnett multiple comparison test). U83A-N blocks chemotaxis of ex vivo human PBMCs induced by (B) 50 nM and 100 nM CCL3 or (C) 10 nM and 50 nM CCL4. Data are means ± SDs of triplicates.