Phagocytosis of Malaria Parasites by the Neutrophil Leukocytes of the Marrow. ∗

It has long been known that malaria plasmodia or their disintegration products must be phagocytized by the neutrophil cells, because pigment granules are frequently seen in the neutrophils in smears from the blood. However, I have never seen, and have been unable to find a record of anyone else who has seen, intact or only partially digested malaria parasites within neutrophil cells in the blood.

The development of the sternal puncture technic for obtaining human bone marrow during life 1 made possible the study of marrow smears in malaria. Examination of these smears revealed not only a higher percentage of the red cells invaded but the presence in the neutrophil leukocytes of malaria parasites in all stages of digestion, from the intact organism to the residual collection of pigment granules. Most of the phagocytizing leukocytes were staff cells but phagocytosis was observed also in segmented neutrophils and neutrophil metamyelocytes. Examination of blood smears made at about the same time that the marrow was taken revealed no evidences of phagocytosis of malaria parasites except the occasional presence of pigment granules in the neutrophils.

Such phagocytosis has been found in all sternal marrows from the 5 cases of inoculation tertian malaria which have so far been available for study. It seems reasonable to believe that this phagocytosis will be found to occur in naturally occurring tertian malaria and in the other forms of malaria.