Effect of various doses of IFN-γ and anti–IFN-γ antibody. Monocytes were either untreated, pretreated for 24 hours with IFN-γ at the concentrations indicated, or pretreated for 24 hours with IFN-γ (500 U/mL) plus anti–IFN-γ antibody. CCR5 expression was determined by flow cytometry. Results are shown as the percentage of cells positive for CCR5 expression (mean  ± SEM) (A) and as the RFI (B) and are representative of 3 cord blood samples and 2 adult donors (*P < .05, **P < .01, IFN-γ vuntreated).