Figure 5

Phagocytosis of troph-p-RBCs and np-RBCs double-labelled with EB and CF-SE. (A) EB fluorescence of a synchronized trophozoite culture with 44% parasitaemia: troph-p-RBCs, black line, np-RBCs, full histogram. (B) CF-SE fluorescence vs EB fluorescence density plots of THP-1 cells fed with non-opsonized or serum-opsonized synchronized trophozoite cultures with 8% and 44% parasitaemia. In both upper (8% parasitaemia) and lower (44% parasitaemia) plots, upper and lower right quadrants show phagocytically active THP-1 cells fed with troph-p-RBCs or np-RBCs, respectively. Cells positive for CF-SE and EB were counted above the fluorescence threshold set in each experiment. One representative experiment out of six with similar results. (C) Phagocytosis of serum-opsonized and non-opsonized troph-p- and np-RBCs by THP-1 cells in synchronized trophozoite cultures with 8% and 44% parasitaemia. Numbers on bars are percentages of phagocytically active (ph)THP-1 cells. For each phTHP-1 value the share of p- and np-RBCs in the sample is indicated. Bar data are mean values of phTHP-1 cells ± SD (N=6). (D) Total phagocytosis of serum-opsonized and non-opsonized p- plus np-RBCs by THP-1 cells in synchronized trophozoite cultures with 8% and 44% parasitaemia. Data are numbers of p- plus np-RBCs phagocytosed per phTHP-1 cell. Bar data are mean values ± SD (N = 6). For details, see Methods.