Nonopsonic phagocytosis of

P falciparum PEs. Synchronized, nonopsonizedP falciparum trophozoite PE cultures were incubated with adherent, Fc receptor–blocked human monocytes in 10% heat-inactivated fetal calf serum for 4 hours as described in “Materials and methods.” Nonadherent erythrocytes were washed away and adherent erythrocytes removed by hypotonic lysis. After washing, monocytes were fixed and prepared for light microscopic examination (A) or for IC4 monoclonal antibody immunofluoresence (B). (A) Three panels of representative monocytes are shown under light microscopy. Each panel contains 1 or 2 monocytes, with several ingested PEs. (B) Three panels of representative monocytes analyzed by IC4 monoclonal antibody immunofluorescence following PE phagocytosis. The typical speckled pattern produced by IC4 binding to the PE surface can be readily appreciated in the ingested PEs. All results shown are indicative of results obtained on at least 3 independent occasions. Original magnification, × 1000.