Phagocytosis of hemozoin (native and synthetic malaria pigment), and Plasmodium falciparum intraerythrocyte-stage parasites by human and mouse phagocytes

Hemozoin, the detoxification product of hemoglobin heme, piles up as electr on-dense material in the food vacuole (FV) of intraerythrocytic malaria par asites (malaria pigment). In infected individuals, pigment is internalized by bath circulating and resident phagocytes, thus modulating their function s. Synthetic P-hematin, prepared in vitro from hematin (ferriprotoporphyrin IX hydroxide) in acidic condition, is spectroscopically identical to hemoz oin. In this electron microscopy study, native and synthetic hemozoin also prove to be morphologically indistinguishable (large polygonal crystals wit h apparent transverse banding) and to undergo the same process when interna lized by phagocytes (primarily a direct uptake of crystals, similar to what is described for asbestos fibers). On the contrary, whole parasites appear to follow a classical endocytic pathway. This suggests that there may be d ifferences between the ingestion of free particles and whole parasites in t erms of modulation of phagocytes' functions.