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The influence of opsonins on the bactericidal effect of bovine alveolar macrophages against Pasteurella multocida
Abstract:
Monolayers of bovine alveolar macrophages were infected with smooth and rough strains of Pasteurella multocida to determine their bactericidal function. Heat inactivated normal bovine serum, fresh bovine serum, specific immune serum and a combination of specific immune serum and fresh bovine serum were used as opsonins. A substantial difference in the bactericidal effect of macrophages against the logarithmic and stationary phase p. multocida was observed. Opsonization of the rough strain of P. multocida with the combination of specific immune and fresh serum increased their association with alveolar macrophages compared to those opsonized with either normal serum, fresh serum or specific immune serum. Opsonization of the smooth strain of P. multocida with normal bovine serum resulted in substantially fewer bacteria associated with macrophages at time zero, compared with other opsonins. Regardless of the kind of opsonins used in these experiments, the number of the rough strain of P. multocida killed by macrophages was always higher than those of the smooth strain.
Insights
Bovine alveolar macrophages showed different bactericidal effects against smooth and rough Pasteurella multocida strains. Opsonization enhanced bacterial association and killing, with rough strains being more susceptible to macrophage-mediated clearance.
Area of Science:
- Veterinary Immunology
- Bacteriology
- Cellular Microbiology
Background:
- Bovine alveolar macrophages are crucial for lung immunity.
- Pasteurella multocida exists in smooth and rough forms, impacting virulence.
- Opsonization is key for phagocyte-mediated bacterial clearance.
Purpose of the Study:
- To compare the bactericidal function of bovine alveolar macrophages against smooth and rough Pasteurella multocida.
- To investigate the role of different opsonins in macrophage-bacterial interactions.
Main Methods:
- Bovine alveolar macrophages were cultured and infected with smooth and rough P. multocida strains.
- Various opsonins were used: normal bovine serum, fresh bovine serum, specific immune serum, and combinations.
- Bacterial association and killing by macrophages were quantified.
Main Results:
- Macrophage bactericidal activity differed significantly between logarithmic and stationary phase P. multocida.
- Opsonization with combined specific immune and fresh serum enhanced rough strain association with macrophages.
- Rough P. multocida strains were killed more effectively by macrophages than smooth strains, irrespective of opsonin type.
Conclusions:
- Bovine alveolar macrophage bactericidal function is influenced by bacterial strain morphology (smooth vs. rough) and growth phase.
- Specific immune and fresh serum combinations optimize opsonization for rough P. multocida clearance.
- Rough P. multocida strains are generally more susceptible to macrophage-mediated killing than smooth strains.