Nonoxidative microbicidal activity in normal human alveolar and peritoneal macrophages

Area of Science:

• Immunology
• Cell Biology
• Parasitology

Background:

• Toxoplasma gondii multiplies in murine macrophages but is killed by rat macrophages via nonoxidative means.
• Human alveolar macrophage responses to T. gondii are inconsistently reported.
• Investigating human macrophage mechanisms against T. gondii is of significant interest.

Purpose of the Study:

• To investigate the effect of normal human alveolar and peritoneal macrophages on Toxoplasma gondii.
• To determine if human macrophages utilize oxidative or nonoxidative mechanisms to control T. gondii.

Main Methods:

• Human alveolar and peritoneal macrophages were incubated with T. gondii in vitro.
• Parasite load was quantified over time.
• Superoxide production assays and scavenger experiments were performed.

Main Results:

• Human alveolar macrophages significantly inhibited T. gondii multiplication and killed the parasite.
• Human peritoneal macrophages also demonstrated killing of T. gondii.
• Neither alveolar nor peritoneal macrophages exhibited an oxidative burst when exposed to T. gondii.
• Superoxide scavengers did not affect the killing of T. gondii by human macrophages.

Conclusions:

• Normal human alveolar and peritoneal macrophages possess a potent ability to kill T. gondii.
• These macrophages employ nonoxidative mechanisms to eliminate the intracellular parasite.
• Nonoxidative mechanisms may be critical for controlling other opportunistic intracellular pathogens.