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Porphyromonas gingivalis induces ultrastructural and cytoskeletal changes in adherent human polymorphonuclear
M A Scragg1, M J Kelly, D M Williams
1Department of Oral Pathology, St. Bartholomew's and the Royal London School of Medicine and Dentistry, UK. m.a.scragg@mds.qmw.ac.uk
Abstract:
The response of polymorphonuclear leucocytes (PMN) from healthy humans to culture supernatant from the periodontopathogen, Porphyromonas gingivalis, was examined using light, fluorescence and electron microscopy. Exposure of adherent cells to bacterial culture supernatant resulted in a 4-fold increase in the proportion of spread, flattened PMN. Scanning and transmission electron microscopy demonstrated that these cells had long dendritic cytoplasmic projections closely adherent to the substratum, in contrast with the more rounded, less adherent, control PMN. These shape changes were accompanied by a mean reduction in granule density to 57% compared with control cells (p<0.05) and a reduction in F-actin levels to 62% of controls (p<0.001), but no loss of viability and suggest a bacterially-induced mechanism of suppression of PMN motility which is likely to contribute to the pathogenic potential of P. gingivalis.
Insights
Porphyromonas gingivalis supernatant suppresses polymorphonuclear leucocyte (PMN) motility. This bacterial mechanism, observed via microscopy, involves PMN shape changes and reduced granule density, contributing to periodontal disease pathogenesis.
Area of Science:
- Immunology
- Microbiology
- Cell Biology
Background:
- Periodontal disease is linked to the bacterium Porphyromonas gingivalis.
- Polymorphonuclear leucocytes (PMNs) are crucial immune cells in combating oral pathogens.
Purpose of the Study:
- To investigate the effects of P. gingivalis culture supernatant on human PMN morphology and function.
- To elucidate potential mechanisms by which P. gingivalis may evade the host immune response.
Main Methods:
- Human PMNs were exposed to P. gingivalis culture supernatant.
- Light, fluorescence, and electron microscopy were employed to assess PMN morphology and cytoskeletal changes.
- Granule density and F-actin levels were quantified.
Main Results:
- Bacterial supernatant induced a 4-fold increase in spread, flattened PMNs with dendritic projections.
- Significant reductions in PMN granule density (57%) and F-actin levels (62%) were observed.
- No loss of PMN viability was detected, indicating suppressed motility rather than cell death.
Conclusions:
- P. gingivalis supernatant actively suppresses PMN motility through morphological alterations and reduced cytoskeletal components.
- This suppression mechanism likely contributes to the pathogenic potential of P. gingivalis in periodontal disease.
- The findings highlight a novel bacterial strategy for immune evasion in the oral cavity.