U83A and U83A-N inhibition of CCR5 internalization induced by CCL3. (A-C) U373-MAGI-CCR5E cells were treated with 100 nM CCL3, 50 nM U83A, 100 nM U83A-N alone or in combination. Surface CCR5 was detected by flow cytometry, before chemokine addition and after a 5-minute chemokine incubation compared with isotype control. (D) Preincubation effects with 50 to 100 nM U83A or 100 to 500 nM U83A-N was followed by stimulation with 100 nM CCL3 (representative of 2 experiments in duplicate; mean ± SDs).