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Trichomonacidal activity of human polymorphonuclear neutrophils: killing by disruption and fragmentation
Abstract:
Polymorphonuclear neutrophils (PMNs) were shown to kill Trichomonas vaginalis in vitro; 10(2)-10(3) trichomonads were incubated with 3 x 10(6) PMNs on tissue culture plates, and surviving organisms were enumerated in pour plates. After 60 min of aerobic incubation at 37 C, 100% (+/- 0) of the trichomonads had been killed, and nitroblue tetrazolium was reduced at the interface between the PMNs and trichomonads. The importance of oxidative microbicidal systems was confirmed by the observations that only 12% +/- 12% of trichomonads were killed under anaerobic conditions and that aerobic killing was eliminated by the addition of catalase or superoxide dismutase. PMNs killed trichomonads in fresh or absorbed serum but not in bovine serum albumin, in heat-inactivated serum, or in the presence of 1 mM trypan blue; this finding suggested a role for alternative pathway activation of complement. Phase-contrast cinemicrography and electron microscopy revealed the pursuit and surrounding of individual trichomonads by groups of PMNs that were able to fragment the large protozoa and to phagocytize the pieces.
Insights
Polymorphonuclear neutrophils (PMNs) effectively kill Trichomonas vaginalis in vitro through oxidative mechanisms. This study highlights the role of PMNs in combating this protozoan parasite, suggesting potential therapeutic avenues.
Area of Science:
- Immunology
- Parasitology
- Microbiology
Background:
- Trichomonas vaginalis is a protozoan parasite responsible for trichomoniasis.
- The host immune response, particularly involving neutrophils, is crucial for controlling parasitic infections.
Purpose of the Study:
- To investigate the in vitro killing capacity of polymorphonuclear neutrophils (PMNs) against Trichomonas vaginalis.
- To elucidate the mechanisms underlying PMN-mediated killing of T. vaginalis.
Main Methods:
- In vitro incubation of T. vaginalis with PMNs under aerobic and anaerobic conditions.
- Assessment of parasite viability using pour plates.
- Enzyme assays (nitroblue tetrazolium reduction) and use of inhibitors (catalase, superoxide dismutase).
- Microscopy techniques including phase-contrast cinemicrography and electron microscopy.
Main Results:
- PMNs achieved 100% killing of T. vaginalis within 60 minutes under aerobic conditions.
- Oxidative microbicidal systems were essential, as killing was significantly reduced under anaerobic conditions and inhibited by catalase or superoxide dismutase.
- PMN-mediated killing was dependent on serum factors, suggesting complement involvement, and was not observed in the presence of trypan blue.
- Microscopy revealed PMNs surrounding, fragmenting, and phagocytizing T. vaginalis.
Conclusions:
- PMNs exhibit potent in vitro microbicidal activity against T. vaginalis.
- Oxidative mechanisms and complement activation play significant roles in PMN-mediated killing of T. vaginalis.
- These findings underscore the importance of neutrophils in the host defense against T. vaginalis infections.