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A role for activated macrophages in resistance to infection with Toxoplasma
Abstract:
Activated macrophages from mice which were chronically infected with Toxoplasma gondii or Besnoitia jellisoni, or which had received Freund complete adjuvant, had an enhanced capacity to to kill intracellular Toxoplasma. Enhanced killing by activated macrophages was demonstrated by decreased incorporation of isotopically labeled uridine by intracellular Toxoplasma and by inhibition of plaque formation. The latter resulted from lack of proliferation of the intracellular Toxoplasma which is normally followed by destruction of the host cell (macrophage) and secondary invasion and destruction of fibroblast monolayers.
Insights
Activated macrophages, induced by chronic infections or adjuvants, show enhanced killing of intracellular Toxoplasma gondii. This improved parasite control was evident through reduced uridine incorporation and inhibited plaque formation, crucial for host defense strategies.
Area of Science:
- Immunology
- Parasitology
- Cell Biology
Background:
- Macrophages play a critical role in host defense against intracellular pathogens.
- Chronic infections and certain immune stimuli can modulate macrophage function.
- Toxoplasma gondii is an intracellular parasite that infects macrophages.
Purpose of the Study:
- To investigate the effect of chronic infection and immune activation on macrophage parasiticidal capacity.
- To determine if activated macrophages exhibit enhanced killing of intracellular Toxoplasma gondii.
- To elucidate the mechanisms underlying this enhanced parasite killing.
Main Methods:
- Mice were chronically infected with Toxoplasma gondii or Besnoitia jellisoni, or treated with Freund complete adjuvant.
- Macrophage activation status was assessed.
- Intracellular parasite burden was quantified by measuring isotopically labeled uridine incorporation by Toxoplasma.
- Parasite proliferation and host cell destruction were evaluated by plaque formation assays.
Main Results:
- Macrophages from chronically infected or adjuvant-treated mice demonstrated an enhanced ability to kill intracellular Toxoplasma gondii.
- Reduced incorporation of labeled uridine by intracellular parasites indicated decreased Toxoplasma proliferation.
- Inhibition of plaque formation, a measure of parasite-induced cell lysis and spread, was observed.
Conclusions:
- Immune activation, through chronic infection or adjuvant administration, significantly enhances macrophage-mediated killing of Toxoplasma gondii.
- This enhanced killing is linked to suppressed parasite proliferation and reduced host cell destruction.
- Findings highlight the potential of modulating macrophage activity for controlling intracellular parasitic infections.