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Attachment and ingestion of gonococci human neutrophils
Abstract:
Previous studies have indirectly shown that type 1 gonococci are more resistant to phagocytosis by human neutrophils (PMN) than type 3 gonococci. Using phase contrast, fluorescent, and light microscopy, we directly quantitated PMN-gonococcal interaction, with emphasis on separating ingestion from attachment. PMN monolayers were incubated on slides with type 1 or type 3 gonococcal fluorescent antibody (FA). After methanol fixation, the FA-stained gonococci associated with PMN were cointed. Since the live PMN excludes FA, the FA-stained gonococci represent only extracellular gonococci. Methylene blue was then added to the smae slide to stain both ingested and surface attached gonococci. Using these methods, intracellular and extracellular cell-associated gonococci were quantitated under varying conditions. The numbers of methylene blue-stained cell-associated gonococci that were ingested were: with normal serum, 3.7 plus or minus 4.1 per cent for type 1 and 56.2 plus or minus 3.7 percent for type 3 (P smaller than 0.001); with heat-inactivated serum, 1.0 plus or minus 3.0 per cent for type 1 and 52.6 plus or minus 3.7 per cent for type 3 (P smaller than 0.001); with higher-titer anti-gonococcal antibody serum, 4.8 plus or minus 4.3 percent for type 1 and 64.0 plus or minus 1.6 per cent for type 3 (P smaller than 0.001). Thus, most type 3 organisms were ingested, but most type 1 gonococci were bound on the PMN surface.
Insights
Type 3 gonococci are readily ingested by human neutrophils (PMN), unlike type 1 gonococci which primarily attach to the cell surface. This study quantifies gonococcal phagocytosis differences.
Area of Science:
- Immunology
- Microbiology
- Cell Biology
Background:
- Neisseria gonorrhoeae exhibits distinct serotypes with varying virulence factors.
- Previous research suggested differences in phagocytosis resistance between gonococcal types.
- Human neutrophils (PMN) are critical immune cells involved in combating bacterial infections.
Purpose of the Study:
- To directly quantify the interaction between type 1 and type 3 gonococci with human neutrophils.
- To differentiate between the attachment and ingestion phases of phagocytosis.
- To investigate the influence of serum and antibodies on this interaction.
Main Methods:
- Utilized phase contrast, fluorescent, and light microscopy for direct visualization.
- Employed fluorescent antibody staining to identify extracellular gonococci.
- Used methylene blue staining to identify both ingested and surface-attached gonococci.
- Quantitated intracellular and extracellular gonococci under various conditions, including different serum types.
Main Results:
- Type 3 gonococci showed significantly higher ingestion rates by PMN compared to type 1 gonococci across all tested conditions (P < 0.001).
- With normal serum, type 3 ingestion was 56.2% vs. 3.7% for type 1.
- Heat-inactivated serum and anti-gonococcal antibody serum did not alter this differential phagocytosis pattern.
- Type 1 gonococci predominantly remained attached to the PMN surface, while type 3 were largely ingested.
Conclusions:
- Type 3 gonococci are significantly more susceptible to phagocytosis by human neutrophils than type 1 gonococci.
- The observed differences in phagocytosis are primarily due to variations in bacterial uptake, not just attachment.
- These findings highlight distinct mechanisms of immune evasion between gonococcal types.