Co-capping of CD9 with MHC class II and CD38. Purified monocytes untreated (A, C, E, G) or pretreated with 10 mM MβCD (B, D, F, H) were incubated with CD38 (A-D) or CD9 (E-H) mAbs (10 μg/mL) for 20 minutes on ice and subsequently with Texas red–conjugated goat anti–mouse Ig for 45 minutes at 22°C to allow complete capping. Cells were then stained with the indicated FITC-conjugated mAbs and analyzed. Confocal optic sections for the merged images of representative cells are shown.