Reaction of anti-Pg mAbs with cell-bound Pg. U937 cells (3 × 10⁷/mL) were incubated without (gray) or with (black) 20μM Pg for 30 minutes at 37°C. Then anti-Pg mAbs were added and detection was with FITC-labeled goat anti–mouse IgG (B-G). Controls with second Ab only without (gray) or with (black) 20μM Pg or with isotype control IgG in the presence of 20μM Pg (dashed lines) are in panel A.