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Fasciola hepatica: free radical generation by peritoneal leukocytes in challenged rodents
N C Smith1, K S Ovington, J C Boray
1Department of Zoology, Australian National University, Canberra.
Abstract:
Free radical generation by peritoneal leukocytes from hosts able to develop resistance to reinfection with Fasciola hepatica (rats) was compared with that of hosts unable to develop resistance (mice). Free radical generation by rat leukocytes was 3.5 times higher per cell and 30 times higher per animal than radical production by mouse leukocytes. The capacity of peritoneal leukocytes to produce free radicals in response to adult fluke crude antigen was increased by the presence of host plasma and was quantitatively greater in challenged rats than in naive or primary infected rats. This was not the case for mice, in which cells from primary infected animals were equally as responsive as cells from challenged mice. Further experiments revealed that challenge infection in rats apparently caused the in vivo activation of peritoneal leukocytes and increased levels of unidentified factors in plasma and that both of these responses were involved in the initiation of free radical generation in response to F. hepatica. Dramatic increases in the number of eosinophils present in the peritoneal cavities of primary infected and challenged rats (but not mice) were observed but the role of eosinophils in the production of free radicals in response to F. hepatica remains to be determined.
Insights
Rats generate significantly more free radicals from peritoneal leukocytes than mice when exposed to Fasciola hepatica antigens. This enhanced free radical generation in rats is linked to in vivo leukocyte activation and plasma factors, suggesting a role in resistance to parasitic infection.
Area of Science:
- Immunology
- Parasitology
- Biochemistry
Background:
- Fasciola hepatica infection elicits varying host responses.
- Understanding immune cell function, like free radical generation, is crucial for developing effective treatments.
Purpose of the Study:
- To compare free radical generation by peritoneal leukocytes in rats (resistant) and mice (non-resistant) infected with Fasciola hepatica.
- To investigate factors influencing free radical production in response to parasitic antigens.
Main Methods:
- Peritoneal leukocytes were isolated from naive, primary infected, and challenged rats and mice.
- Free radical generation was measured in response to adult fluke crude antigen.
- The influence of host plasma and in vivo activation was assessed.
Main Results:
- Rat leukocytes produced substantially higher levels of free radicals compared to mouse leukocytes.
- Host plasma enhanced free radical production in rats, with challenged rats showing the highest response.
- In vivo activation of leukocytes and plasma factors were identified as key contributors to enhanced free radical generation in rats.
- Eosinophil infiltration was noted in rats but not mice, though their role remains unclear.
Conclusions:
- Rats exhibit a more robust free radical response to Fasciola hepatica infection than mice.
- In vivo leukocyte activation and plasma factors play a significant role in the enhanced immune response observed in resistant hosts.
- Further research is needed to elucidate the specific role of eosinophils in this process.