Studies on the effect of the anti-phagocytic agent cytochalasin B on Leishmania-macrophage interaction
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Abstract:
Mouse peritoneal exudate cells were cultured on coverslips in Eagle's Basal Essential Medium. The adhering cells were infected with promastigotes of three different species of Leishmania. After 8 h incubation, the macrophages were fixed and stained, and a total of one hundred cells were counted. The rates of infection of macrophages were respectively 53.5 +/- 5% for L. enriettii, 52.3 +/- 5% for L. donovani and 11.7 +/- 2% for L. tropica. When cytochalasin B at concentrations of 2.5, 5 and 10 microgram/ml and Leishmania promastigotes were added to the adhering cells at the same time, the drug did not have any effect on the uptake of the organisms by the macrophages. However, when the cells were treated for a 2-h period with the drug and then were infected with the promastigotes, only 1-2% of the cells were infected. On the other hand, when cytochalasin B-treated cells which had lost their phagocytic ability were washed and then were infected with the promastigotes, some degree of cellular infection was observed. It was concluded that infection of mouse p.e.c. by three different species of Leishmania which were used in our study was by phagocytosis rather than active penetration of the organisms into the cells. It was also of interest to note that although our outbred strain of mice gets infected easily with L. tropica, the p.e.c. of these animals phagocytosed L. tropica with least efficiency in comparison with L. donovani and L. enriettii.
Insights
Mouse macrophages engulf Leishmania parasites through phagocytosis, not active penetration. Cytochalasin B inhibits this process, highlighting the role of phagocytosis in Leishmania infection.
Area of Science:
- Immunology
- Cell Biology
- Parasitology
Background:
- Leishmania species infect macrophages, the primary host cells.
- The mechanism of Leishmania entry into macrophages is crucial for understanding infection dynamics.
Purpose of the Study:
- To investigate the mechanism of Leishmania entry into mouse peritoneal exudate cells (PECs).
- To determine the role of phagocytosis in Leishmania infection.
- To assess the effect of cytochalasin B on Leishmania uptake by macrophages.
Main Methods:
- Culturing mouse PECs on coverslips.
- Infecting macrophages with promastigotes of Leishmania enriettii, L. donovani, and L. tropica.
- Treating cells with cytochalasin B at various concentrations.
- Quantifying infection rates by counting stained cells.
Main Results:
- Macrophages showed high infection rates for L. enriettii (53.5%) and L. donovani (52.3%), and lower for L. tropica (11.7%).
- Cytochalasin B did not affect uptake when added simultaneously with parasites.
- Pre-treatment with cytochalasin B significantly reduced infection rates to 1-2%, indicating inhibition of phagocytosis.
- Washing cytochalasin B-treated cells partially restored infection, suggesting phagocytosis is essential.
Conclusions:
- Leishmania infection of mouse PECs occurs via phagocytosis, not active cell penetration.
- Cytochalasin B's inhibitory effect confirms the dependence of parasite entry on active phagocytic processes.
- Despite susceptibility to L. tropica infection, mouse PECs exhibit lower phagocytic efficiency for this species compared to L. donovani and L. enriettii.