Falciparum malaria in naturally infected human patients: IV--Ultrastructural changes in peripheral white blood cells

Ultrastructure of white blood cells (WBC) were studied in peripheral venous blood from Saudi patients with acute falciparum malaria (AFM) and compared with their counterparts in same patients 2 weeks after chloroquine treatment and full recovery. A counting system was incorporated to determine the rate of abnormal to normal cell type in plastic thick sections during the course of the disease. Neutrophilia, monocytosis, eosinopenia and lymphocytosis were associated with various ultrastructural abnormalities including: (1) Knobby phagocytic polymorphonuclear neutrophils (PMN) and promyelocytes, and PMN with highly vacuolated cytoplasm. (2) Irregularly outlined electron-dense nuclei in non-functional monocytes. (3) Unusual distribution of nuclear chromatin in resting B-lymphocytes, while others possess highly vacuolated cytoplasm and knobby surfaces. (4) Absence of granules in granular lymphocytes containing the known diagnostic paratubular crystalline arrays. (5) Plasmablasts containing electron-dense granules and swollen mitochondria. These abnormalities were suggested to be due to the high level of parasitaemia producing some toxic soluble products. They may also be attributed to alteration of bone marrow macrophages as a sequence of their interaction with soluble parasite products or their phagocytic parasitized red cells and debris released during the rupture of schizonts. This study showed that the number of abnormal WBC increases in patients with high level of parasitaemia; plasmablasts have the lowest rate of abnormalities, while monocytes have the highest; old patients present with lower degree of parasitaemia than young patients due to a less mature immune system; and the AFM may have independent effects on the structure of human WBC.