Electron Microscopy of Intracellular Protozoa.
Rept. no. 2 (Annual),
CASE WESTERN RESERVE UNIV CLEVELAND OHIO INST OF PATHOLOGY
Pagination or Media Count:
We studied the interactions between macrophages and Leishmania mexicana in vitro in the absence or presence of cytochalasin B, since there has not been a general agreement as to whether or not the promastigotes of Leishmania can actively penetrate the host macrophages. Our study showed that almost 90 of the promastigotes attached to the macrophages with their flagellum within 2 minute incubation periods of the parasite and macrophages. On the other hand, the macrophages showed many pseudopods and the promastigotes attached to the macrophages without any particular orientation after a 5 minute incubation period. These observations indicate that the promastigotes of L. mexicana enter into the macrophages actively with the flagellum end first during the first 2 minute interaction period. However, when the macrophages become actively phagocytic after a 5 minute interaction period, many of the parasites are phagocytosed by the macrophages. Therefore, we conclude that the promastigotes of Leishmania mexicana initially invade the macrophages actively, but they are also phagocytosed by the macrophages to gain entry when the macrophages become actively phagocytic in the later stage of the interaction. Studies on the invasion of the erythrocytes by malarial merozoites demonstrated that the formation of a junction between the merozoite and the erythrocyte is essential for successful erythrocyte entry by a merozoite. However, the exact nature of this junction was difficult to analyze by the thin-sectioning technique alone.
- Medicine and Medical Research