Erythrocyte membrane alterations induced by Plasmodium simium infection in Saimiri sciureus: relation to Schuffner's dots

The nature of erythrocyte membrane alterations in Plasmodium simium infections was determined employing light microscopy, carbon replication and transmission electron microscopy. Light microscopy of Giemsa stained preparations shows that infected cells initially acquire a faint stippling (schuffnerization) which becomes pronounced with subsequent parasite development. Enlargement of the host cell usually accompanied stippling. Both phenomena appear to depend on host cell age since infected mature erythrocytes were neither stippled nor enlarged. Carbon replicas show numerous indentations over the outer membrane surface of most infected cells. Their distribution suggests that they account for Schuffner's granules. The surface indentations are manifest as small infundibula which open to the infected cell's surface. Cytoplasmic microvesicles in the infected cell's stroma frequently are observed adjacent or catenated to the surface infundibula. Images suggest their fusion with the surface infundibula thus adding membrane to the cell's surface and accounting for host cell enlargement.