Phagocytosis rate in the presence of scFvs.
(A) Highly synchronous blood-stage cultures of P falciparumwere cocultured with PBMCs (2 × 105/well) in the presence or absence of scFvs (50 μg/mL) for 24 or 72 hours in a 96-well plate. The rate of phagocytosis was evaluated by counting the number of cells ingesting one or more P falciparummerozoites per 500 monocytes. Results are presented as the means ± SDs of 3 separate experiments performed in triplicate. *P < .05 compared with 5.2 scFv and OKT3 scFv. (B) Also shown are examples of the phagocytosis. Photomicrographs of Giemsa-stained smears of in vitro P falciparum cocultured with PBMCs in the presence of 5.2-OKT3 biscFv. Many clusters of parasites phagocytosed by monocytes were observed when P falciparum was cultured with 5.2-OKT3 biscFv and PBMCs. (i) Monocytes actively phagocytosing parasites. (ii) Agglutinated clusters of merozoite phagocytosis. (iii) Monocytes phagocytosing parasites and crisis forms of parasites. CF indicates crisis form; P, malaria pigment. Original magnification, × 1000.
