Pitting function of the spleen in malaria: ultrastructural observations.

Ultrastructural studies of spleens from monkeys infected with Plasmodium knowlesi suggest that the spleen removes or "pits" malaria parasites from red cells. This function may explain the presence of nonparasitized spherocytic erythrocytes in the peripheral blood and may in part account for the discrepancy between the excessive hemolysis and the number of parasitized erythrocytes in animals with experimentally induced malaria.