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Inhibition of human polymorphonuclear leukocyte respiratory burst, bactericidal activity, and migration by
Abstract:
The in vitro effects of pneumolysin, a sulfhydryl-activated toxin produced by Streptococcus pneumoniae, on various functions of human polymorphonuclear leukocytes (PMNLs) was investigated. Treatment of PMNLs with highly purified toxin significantly inhibited respiratory burst (in response to stimulation), ability to kill opsonized pneumococci, chemotaxis, and random migration. These inhibitions were observed at very low toxin doses (less than or equal to 1 hemolytic unit (2 ng) per 10(6) PMNLs), which had no effect on PMNL viability. These results suggest that pneumolysin could function in pathogenicity by interfering with the ability of PMNLs to migrate toward and kill pneumococci.
Insights
Pneumolysin, a toxin from Streptococcus pneumoniae, impairs human immune cell functions like migration and bacterial killing. Even at low doses, this toxin interferes with polymorphonuclear leukocytes (PMNLs) crucial for fighting infection.
Area of Science:
- Immunology
- Microbiology
- Toxicology
Background:
- Streptococcus pneumoniae is a major cause of bacterial infections.
- Pneumolysin is a key virulence factor produced by S. pneumoniae.
- Human polymorphonuclear leukocytes (PMNLs) are critical immune cells for combating bacterial pathogens.
Purpose of the Study:
- To investigate the in vitro effects of pneumolysin on human PMNL functions.
- To determine the impact of pneumolysin on immune cell responses to S. pneumoniae.
Main Methods:
- Treatment of human PMNLs with purified pneumolysin toxin.
- Assessment of PMNL functions including respiratory burst, bacterial killing, chemotaxis, and migration.
- Evaluation of toxin effects at low doses and impact on PMNL viability.
Main Results:
- Pneumolysin significantly inhibited PMNL respiratory burst, killing of opsonized pneumococci, chemotaxis, and random migration.
- These inhibitory effects occurred at very low toxin concentrations (≤1 hemolytic unit/10^6 PMNLs).
- PMNL viability was not affected at the concentrations causing functional inhibition.
Conclusions:
- Pneumolysin interferes with critical human PMNL functions essential for pathogen clearance.
- The toxin's ability to impair PMNL migration and killing contributes to its role in S. pneumoniae pathogenicity.
- Pneumolysin represents a potential therapeutic target for managing pneumococcal infections.