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Activation of polymorphonuclear leukocytes by salmonella
Abstract:
The interaction of polymorphonuclear leukocytes (PMN) with salmonella, as studied by chemiluminescence and phagocytosis, was very different for a number of clinical isolates. Particularly bacteria in the serogroups C1 and E4 deviated from other Salmonella. The differences were observed in the rate of activation, peak value, duration of the chemiluminescence, and in the extent of association and ingestion as studied microscopically. Old laboratory S-strains such as Salmonella typhimurium 395 MS and S. minnesota S99 , which did not associate with the PMN, showed little activation of the PMN, whereas their phagocytosis-sensitive R-mutants induced rapid activation, high peak values, and short duration of the chemiluminescence. Certain isolates belonging to the C1/E4 group induced intermediate types of reactions. The kinetics of the activation was related to the physicochemical surface properties of the bacteria. Heating the bacteria at 70 degrees C for 45 min enhanced the activation of PMN by the S-type strains conspicuously but in different ways, whereas that of R-mutants was delayed. Different clinical isolates of salmonella have shown different physico-chemical surfaces, liability to phagocytosis by PMNs and different degrees of eliciting inflammatory mediators from PMNs in vitro. The results indicate that the C1/E4 group of Salmonella has pathogenicity mechanisms different from most salmonellae.
Insights
Salmonella serogroups C1 and E4 exhibit distinct interactions with polymorphonuclear leukocytes (PMN), suggesting unique pathogenicity mechanisms. These differences in bacterial surface properties influence PMN activation and phagocytosis, impacting host immune responses.
Area of Science:
- Immunology
- Microbiology
- Bacterial Pathogenesis
Background:
- Polymorphonuclear leukocytes (PMN) are crucial innate immune cells involved in combating bacterial infections.
- Salmonella species are significant human pathogens, with varying degrees of virulence.
- Understanding bacterial interactions with immune cells is key to deciphering pathogenesis.
Purpose of the Study:
- To investigate the differential interactions between clinical Salmonella isolates and human PMNs.
- To characterize the influence of bacterial surface properties on PMN activation and phagocytosis.
- To identify potential differences in pathogenicity mechanisms among Salmonella serogroups.
Main Methods:
- Chemiluminescence assays to measure PMN activation.
- Phagocytosis assays using microscopy to assess bacterial association and ingestion.
- Analysis of physicochemical surface properties of bacterial isolates.
- Heat treatment of bacteria to study its effect on PMN interaction.
Main Results:
- Significant variations in PMN activation kinetics (rate, peak, duration) were observed among Salmonella isolates.
- Salmonella serogroups C1 and E4 displayed distinct interaction patterns with PMNs compared to other serogroups.
- Bacterial surface properties correlated with the extent of PMN activation and phagocytosis.
- Heat treatment differentially affected PMN activation by smooth (S) and rough (R) strains.
Conclusions:
- Clinical Salmonella isolates, particularly those in serogroups C1 and E4, possess unique mechanisms for interacting with PMNs.
- Bacterial surface characteristics play a critical role in modulating innate immune responses.
- These findings suggest that Salmonella serogroups C1 and E4 may employ distinct pathogenicity strategies.