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Interaction of Leishmania with a macrophage cell line. Correlation between intracellular killing and the generation
Abstract:
The promastigote form of Leishmania donovani and Leishmania tropica, the etiologic agents of visceral and cutaneous leishmaniasis, respectively, readily parasitize unstimulated J774G8 macrophage-like cells, whereas 80-95% of the same promastigotes are killed within resident macrophages from normal BALB/c mice. This striking difference in intracellular anti-leishmanial activity correlated closely with the capacity to generate toxic oxygen intermediates. Thus, after triggering with phorbol myristate acetate or phagocytosis of zymosan or promastigotes, 90% of the J774G8 cells failed to reduce nitroblue tetrazolium, and released 5-10-fold less O2- and H2O2 than BALB/c macrophages. Exposure to concanavalin A-stimulated lymphokine, however, effectively enhanced the oxidative response of J774G8 cells, and, similarly, induced intracellular anti-leishmanial activity. Inhibiting macrophage H2O2 production consistently decreased the killing of Leishmania by lymphokine-treated J774G8 cells. These observations illustrate the usefulness of examining homogeneous macrophage cell lines that are deficient in a particular effector function, and also serve reemphasize the important role of oxygen intermediates in the microbicidal response of mononuclear phagocytes to intracellular parasites.
Insights
Leishmania parasites infect macrophage-like cells but are killed by normal mouse macrophages. This difference is due to toxic oxygen intermediates, crucial for fighting intracellular parasites.
Area of Science:
- Immunology
- Cell Biology
- Parasitology
Background:
- Leishmania donovani and Leishmania tropica cause visceral and cutaneous leishmaniasis.
- Macrophage-like cell lines and primary macrophages exhibit differential anti-leishmanial activity.
- This difference is linked to the production of reactive oxygen species.
Purpose of the Study:
- To investigate the role of toxic oxygen intermediates in the differential killing of Leishmania by macrophages.
- To explore the potential of enhancing macrophage effector functions.
Main Methods:
- Comparison of Leishmania killing by J774G8 macrophage-like cells and normal BALB/c mouse macrophages.
- Measurement of toxic oxygen intermediate production (nitroblue tetrazolium reduction, superoxide, hydrogen peroxide).
- Assessment of the effect of concanavalin A-stimulated lymphokine on macrophage oxidative response and anti-leishmanial activity.
Main Results:
- J774G8 cells showed significantly less killing of Leishmania and produced fewer toxic oxygen intermediates compared to BALB/c macrophages.
- Lymphokine treatment enhanced the oxidative response and anti-leishmanial activity of J774G8 cells.
- Inhibition of hydrogen peroxide production reduced Leishmania killing in lymphokine-treated J774G8 cells.
Conclusions:
- Toxic oxygen intermediates play a critical role in the microbicidal activity of mononuclear phagocytes against Leishmania.
- Macrophage cell lines deficient in specific effector functions are valuable tools for studying host-parasite interactions.
- Enhancing macrophage oxidative responses can improve their ability to combat intracellular parasitic infections.