Macrophage procoagulant activity in experimental African trypanosomiasis

Area of Science:

• Immunology
• Parasitology
• Hematology

Background:

• Peritoneal macrophages play a key role in immune responses.
• Trypanosoma brucei brucei infection in mice leads to significant immunological changes.
• Procoagulant activity (PCA) in macrophages is crucial for hemostasis.

Purpose of the Study:

• To investigate the changes in procoagulant activity (PCA) of peritoneal macrophages during Trypanosoma brucei brucei infection.
• To determine the relationship between parasite pathogenicity and macrophage PCA.
• To explore the mechanism of macrophage activation by trypanosomes.

Main Methods:

• Induction of Trypanosoma brucei brucei and T. musculi infections in mice.
• Measurement of peritoneal macrophage procoagulant activity (PCA).
• Assessment of macrophage lysosomal enzyme secretion.
• In vitro stimulation of macrophages with trypanosomes (intact and decapsidated).

Main Results:

• Macrophage PCA was significantly elevated during T. brucei brucei infection, returning to normal after therapy.
• PCA levels correlated with parasite pathogenicity; non-pathogenic T. musculi caused minimal changes.
• Macrophages became hyperresponsive to zymosan stimulation for PCA but hyporesponsive for lysosomal enzyme secretion.
• Decapsidation of trypanosomes rendered them highly stimulatory for macrophages, suggesting indirect activation.

Conclusions:

• Elevated macrophage PCA during trypanosome infection may contribute to coagulation abnormalities.
• Parasite pathogenicity, rather than mere presence, influences macrophage PCA.
• Trypanosomes may indirectly activate macrophages, possibly via their glycoprotein coat, leading to altered immune cell function.