CCR5 protein expression on monocytes. (A) Flow cytometry analysis: Monocytes were incubated for 48 hours with medium or PGE₂ (10⁻⁵ mol/L) before labeling either with FITC-conjugated goat anti-mouse antibody alone (dotted line) or with anti-CCR5 (2D7) antibody followed by FITC-conjugated goat anti-mouse antibody (untreated cells: thick line; PGE₂-treated cells: thin line). Representative experiment of eight independent experiments. (B) Laser confocal microscopy: Monocytes were incubated for 48 hours with medium (left) or PGE₂ (10⁻⁵ mol/L) (middle) before permeabilization and labeling with anti-CCR5 (2D7) antibody followed by rhodamine-conjugated goat anti-mouse antibody. For comparison, monocytes incubated with medium for 48 hours were stimulated with MIP-1β (100 ng/mL) for 30 minutes before labeling, to illustrate CCR5 internalization (right).