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Interaction between human polymorphonuclear leukocytes and two different strains of type 1 fimbriae-bearing
Abstract:
Two type 1 fimbriae-bearing strains of Escherichia coli, ABU2 (ON:K14) and PN7 (O1:K1), with different underlying physicochemical surface properties were compared for their capacity to interact with human polymorphonuclear leukocytes. Both strains attached strongly to neutrophils in a mannose-sensitive manner. One of the strains, ABU2, with a surface exposing weak negative charge and liability to hydrophobic interaction, was efficiently ingested (65%) and caused a release of reactive oxidative metabolites (chemiluminescence) and lysosomal enzymes. The other strains, PN7, exposing a hydrophilic, negatively charged K antigen and hydrophilic uncharged smooth lipopolysaccharide, resisted phagocytosis (only 25% were ingested) but nevertheless caused a release of reactive oxidative metabolites and lysosomal enzymes to a greater extent than did phagocytosed strain ABU2. These results show that attachment mediated by type 1 fimbriae does not ultimately lead to ingestion. Whether the attached bacteria are being ingested or not depends on their underlying physicochemical surface properties. Furthermore, if the bacteria remain extracellularly attached, they may potentiate the inflammatory process.
Insights
Escherichia coli type 1 fimbriae mediate neutrophil attachment. Bacterial surface properties, not just attachment, determine ingestion and inflammatory potential, impacting immune responses.
Area of Science:
- Microbiology
- Immunology
- Biochemistry
Background:
- Escherichia coli strains utilize type 1 fimbriae for host cell adhesion.
- Human neutrophils are key immune cells involved in combating bacterial infections.
- Bacterial surface physicochemical properties influence host-pathogen interactions.
Purpose of the Study:
- To compare the interaction of two type 1 fimbriae-bearing Escherichia coli strains with distinct surface properties with human polymorphonuclear leukocytes.
- To elucidate the role of bacterial surface physicochemical properties in neutrophil ingestion and inflammatory mediator release.
Main Methods:
- Utilized two specific Escherichia coli strains (ABU2 and PN7) with characterized type 1 fimbriae.
- Assessed bacterial attachment to human polymorphonuclear leukocytes (neutrophils).
- Quantified bacterial ingestion, reactive oxidative metabolite release (chemiluminescence), and lysosomal enzyme release.
Main Results:
- Both E. coli strains demonstrated mannose-sensitive attachment to neutrophils via type 1 fimbriae.
- Strain ABU2, with hydrophobic surface properties, was efficiently ingested (65%) and induced significant mediator release.
- Strain PN7, with hydrophilic surface properties, resisted phagocytosis (25% ingestion) but elicited a greater release of inflammatory mediators.
Conclusions:
- Type 1 fimbriae-mediated attachment alone does not guarantee bacterial ingestion by neutrophils.
- Underlying bacterial surface physicochemical properties critically dictate the outcome of neutrophil-bacterial interactions, including phagocytosis.
- Extracellularly attached bacteria, even if not ingested, can significantly contribute to the inflammatory process.