Plasmodium falciparum: Automated assay of erythrocyte invasion using flow cytofluorometry

Erythrocytes labeled with fluorescein isothiocyanate, were mixed with erythrocytes infected with Plasmodium falciparum. After allowing time for invasion of labeled cells to take place, cells were stained with propidium iodide. Parasitemia in labeled cells was determined using flow cytofluorometry. The invasion of labeled erythrocytes was reduced in a dose-dependent manner by immune serum. The degree of inhibition obtained increased as the erythrocyte concentration decreased.