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04:25
Capsular Serotyping of Streptococcus pneumoniae Using the Quellung Reaction
Published on: February 24, 2014
Killing of Streptococcus pneumoniae by capsular polysaccharide-specific polymeric IgA, complement, and phagocytes
E N Janoff1, C Fasching, J M Orenstein
1Infectious Disease Section, Department of Medicine, Veterans Affairs Medical Center and University of Minnesota Medical School, Minneapolis, Minnesota 55417, USA. janof001@tc.umn.edu
The Journal of Clinical Investigation
|October 19, 1999
Summary
Polymeric IgA (pIgA) effectively kills Streptococcus pneumoniae, a common pathogen. This immune response relies on complement and phagocytes, with distinct roles depending on inflammation levels.
Area of Science:
- Immunology
- Microbiology
- Infectious Diseases
Background:
- The role of Immunoglobulin A (IgA) in combating invasive mucosal pathogens like Streptococcus pneumoniae remains unclear.
- Understanding IgA's function is crucial for developing strategies against pneumococcal infections.
Purpose of the Study:
- To investigate the mechanisms by which IgA mediates the clearance of Streptococcus pneumoniae.
- To determine the influence of IgA forms (polymeric vs. monomeric) and complement on pneumococcal killing.
Main Methods:
- Utilized human pneumococcal capsular polysaccharide-specific IgA in dose-dependent killing assays.
- Assessed the roles of complement (alternative pathway), phagocytes, and inflammatory mediators (C5a, TNF-alpha).
- Investigated the involvement of Fcalpha receptor (CD89) and complement receptors (CR1/CR3) in IgA-mediated killing.
Main Results:
- Specific IgA initiated dose-dependent killing of S. pneumoniae with complement and phagocytes.
- Polymeric IgA (pIgA) demonstrated more efficient killing than monomeric IgA.
- IgA-mediated killing by phagocytes required complement via the alternative pathway but could be induced by inflammatory mediators in complement's absence.
Conclusions:
- S. pneumoniae-specific IgA, particularly pIgA, plays a significant role in controlling pneumococcal infections.
- IgA's mechanism of action varies with the presence or absence of inflammation, suggesting distinct roles in mucosal immunity and systemic infections.
- pIgA may be key in managing pneumococcal infections both locally and systemically.
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