151. |
- Åkerström, Bo, et al.
(författare)
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Bacterial surface protein L binds and inactivates neutrophil proteins S100A8/A9.
- 2009
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Ingår i: Journal of immunology. - : The American Association of Immunologists. - 1550-6606 .- 0022-1767. ; 183:7, s. 4583-4592
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Tidskriftsartikel (refereegranskat)abstract
- Finegoldia magna is an anaerobic bacterial species that is part of the normal human flora on all nonsterile body surfaces, but it is also a significant opportunistic pathogen causing a wide range of infections. Some isolates of F. magna that are more frequently associated with clinical infection express protein L, a surface protein containing multiple homologous domains (B1-B5) that bind Igs through interactions with Ig L chains. The present study shows that the N-terminal A domain of protein L binds S100A8/A9, antibacterial proteins present in large amounts in the cytoplasm of neutrophils, but also extracellularly in tissues during inflammation. As a result, protein L-expressing F. magna are protected against killing by S100A8/A9. Igs and S100A8/A9 were found to interact independently with protein L, demonstrating that this bacterial surface protein is capable of manipulating both adaptive and innate immune defense mechanisms.
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152. |
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153. |
- Åkesson, Per, et al.
(författare)
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Streptococcal inhibitor of complement-mediated lysis (SIC): an anti-inflammatory virulence determinant
- 2010
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Ingår i: Microbiology. - : Microbiology Society. - 1465-2080 .- 1350-0872. ; 156, s. 3660-3668
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Tidskriftsartikel (refereegranskat)abstract
- Since the late 1980s, a worldwide increase of severe Streptococcus pyogenes infections has been associated with strains of the M1 serotype, strains which all secrete the streptococcal inhibitor of complement-mediated lysis (SIC). Previous work has shown that SIC blocks complement-mediated haemolysis, inhibits the activity of antibacterial peptides and has affinity for the human plasma proteins clusterin and histidine-rich glycoprotein; the latter is a member of the cystatin protein family. The present work demonstrates that SIC binds to cystatin C, high-molecular-mass kininogen (HK) and low-molecular-mass kininogen, which are additional members of this protein family. The binding sites in HK are located in the cystatin-like domain D3 and the endothelial cell-binding domain D5. Immobilization of HK to cellular structures plays a central role in activation of the human contact system. SIC was found to inhibit the binding of HK to endothelial cells, and to reduce contact activation as measured by prolonged blood clotting time and impaired release of bradykinin. These results suggest that SIC modifies host defence systems, which may contribute to the virulence of S. pyogenes strains of the M1 serotype.
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