CD36 is clustered during PE phagocytosis.

Purified human monocytes were incubated with PE preparations for 4 hours, at which time the cells were extensively washed, adherent erythrocytes lysed, and monocytes fixed in 100% methanol. (A) A typical monocyte that has not ingested any PEs is stained with FITC-labeled anti-CD36 OKM5 and analyzed by immunofluorescent microscopy. The cell outline can be readily appreciated. (B) A monocyte that has ingested 2 PEs. The position of the PEs as determined by light microscopy is indicated by arrows. The cell is stained with FITC-labeled OKM5 antibody; immunofluorescent microscopy demonstrates the dense clustering of CD36 at the site of PE ingestion. (C) After a 4-hour nonopsonic phagocytosis assay, monocytes were fixed in 100% methanol, stained first with the PE-specific IC4 monoclonal antibody, then with Texas red–labeled antimouse secondary, and finally with FITC-labeled anti-CD36 OKM5 antibody. Each panel shows single monocytes that have ingested 1 (right panel) or 2 (left panel) PEs. Note the dense clustering of CD36 (green) surrounding the PEs (red) and colocalizing with them (as evidenced by yellow staining). Results shown are representative of 4 independent experiments.