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Capsular polysaccharide regulates neutrophil complement receptor interactions with type III group B streptococci
M S Edwards1, M R Wessels, C J Baker
1Myers Black Section of Infectious Diseases, Department of Pediatrics, Baylor College of Medicine, Houston, Texas 77030.
Infection and Immunity
|July 1, 1993
Summary
Group B streptococcus capsule impacts neutrophil interactions. Efficient bacterial killing in serum requires complement receptors 1 and 3 ligation for encapsulated strains.
Area of Science:
- Immunology
- Microbiology
- Molecular Biology
Background:
- Type III group B streptococci's capsular polysaccharide is a key virulence factor.
- Understanding capsular polysaccharide's role in neutrophil interactions is crucial for combating infections.
Purpose of the Study:
- To investigate how capsular polysaccharide affects neutrophil complement receptor interactions.
- To determine the specific complement receptors involved in phagocytosis of encapsulated bacteria.
Main Methods:
- Utilized encapsulated, poorly encapsulated, and unencapsulated/asialo mutant strains of type III group B streptococci.
- Employed monoclonal antibody blockade of neutrophil complement receptors (CR1 and CR3) in normal and hypogammaglobulinemic human serum.
- Assessed opsonophagocytosis and bactericidal activity.
Main Results:
- Capsular polysaccharide significantly influenced opsonophagocytosis mediated by complement receptor 3 (CR3).
- Blocking CR1 and CR3 simultaneously enhanced inhibition of phagocytosis for encapsulated strains.
- In antibody-free serum, killing of encapsulated strains was dependent on CR1 and CR3 ligation.
Conclusions:
- Type III group B streptococcal capsular polysaccharide actively regulates interactions with neutrophil complement receptors.
- Effective phagocytic clearance of encapsulated bacteria in non-immune serum necessitates the combined engagement of complement receptors 1 and 3.