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Trichomonas vaginalis: alternative pathway activation of complement
Summary
Human serum can kill Trichomonas vaginalis, but this effect is heat-sensitive. Complement activation, not antibodies, appears responsible for parasite lysis, potentially contributing to vaginitis.
Area of Science:
- Immunology
- Parasitology
- Microbiology
Background:
- Trichomonas vaginalis is a protozoan parasite causing vaginitis.
- The role of human serum in T. vaginalis pathogenesis is not fully understood.
Purpose of the Study:
- To investigate the mechanism of serum-mediated lysis of T. vaginalis.
- To determine the involvement of complement and antibodies in this process.
Main Methods:
- Incubation of T. vaginalis with adult human serum.
- Heat-inactivation of serum to assess complement dependence.
- Indirect immunofluorescence to detect anti-parasite antibodies.
- Treatment with EGTA to inhibit classical complement pathway.
- Measurement of C3 to C3i conversion.
Main Results:
- Human serum lysed T. vaginalis.
- Lytic activity was abolished by heat inactivation, indicating a complement-dependent mechanism.
- No significant increase in anti-T. vaginalis antibodies was observed in donors.
- Classical complement pathway inhibition did not prevent C3 activation.
Conclusions:
- Serum-mediated lysis of T. vaginalis is primarily mediated by the alternative complement pathway.
- Complement activation products released during alternative pathway activation may play a role in trichomonal vaginitis pathogenesis.