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Effects of subclinical bovine paratuberculosis on in-vitro polymorphonuclear neutrophil migration
U Dotta1, R Guglielmino, A Cagnasso
1Department of Animal Pathology, University of Turin, Turin, 10126, Italy.
Abstract:
Migration of polymorphonuclear neutrophils (PMNs) [unstimulated or stimulated with zymosan-activated serum (ZAS)] from 18 cows was measured in a microwell filter assay. Of these animals, 10 were subclinically infected with Mycobacterium paratuberculosis and shown by culture to be excreting the organism in the faeces; the remaining eight were clinically normal and negative for M. paratuberculosis on faecal culture. PMN "net migration" (stimulated minus unstimulated cells) of the infected cows was significantly lower than that of the uninfected cows. Migration of unstimulated cells in the infected cows did not differ from that in the uninfected cows. It would therefore appear that the infection influenced only the migratory response of the ZAS-stimulated cells. 1999 Harcourt Publishers Ltd.
Insights
Subclinical Mycobacterium paratuberculosis infection in cows significantly impairs polymorphonuclear neutrophil (PMN) migration, specifically affecting stimulated cell responses. This finding highlights a potential immune dysfunction in paratuberculosis-infected cattle.
Area of Science:
- Veterinary Immunology
- Bovine Infectious Diseases
- Cellular Immunology
Background:
- Mycobacterium paratuberculosis causes Johne's disease in cattle, leading to significant economic losses in the dairy industry.
- Immune dysfunction, including impaired neutrophil function, is a hallmark of persistent infections.
- Understanding neutrophil migration is crucial for assessing host defense mechanisms against pathogens like M. paratuberculosis.
Purpose of the Study:
- To investigate the effect of subclinical Mycobacterium paratuberculosis infection on the migration capacity of polymorphonuclear neutrophils (PMNs) in cattle.
- To differentiate the migratory responses of unstimulated versus stimulated PMNs in infected and uninfected cows.
Main Methods:
- A microwell filter assay was used to measure the migration of PMNs from 18 cows.
- Cows were categorized into two groups: 10 subclinically infected with M. paratuberculosis (fecal culture positive) and 8 clinically normal controls (fecal culture negative).
- PMN migration was assessed under both unstimulated and zymosan-activated serum (ZAS)-stimulated conditions.
Main Results:
- Subclinically M. paratuberculosis-infected cows exhibited significantly lower "net migration" (stimulated minus unstimulated) of PMNs compared to uninfected controls.
- There was no significant difference in the migration of unstimulated PMNs between infected and uninfected cows.
- The impaired migratory response in infected cows was primarily attributed to the reduced migration of ZAS-stimulated PMNs.
Conclusions:
- Subclinical Mycobacterium paratuberculosis infection in cattle impairs the migratory response of polymorphonuclear neutrophils, particularly when stimulated.
- This suggests that M. paratuberculosis infection affects the chemotactic or activation capacity of neutrophils, potentially compromising host defense.
- The findings indicate a specific immune modulation by M. paratuberculosis affecting neutrophil function in subclinically infected animals.