Related Experiment Video
Updated: Aug 16, 2026
Isolation of Peritoneum-derived Mast Cells and Their Functional Characterization with Ca2+-imaging and Degranulation Assays
Published on: July 4, 2018
Type 1 fimbriate Escherichia coli stimulates a unique pattern of degranulation by human polymorphonuclear leukocytes
R Steadman1, N Topley, D E Jenner
1Kidney Research Unit for Wales Foundation Institute Royal Infirmary, Cardiff, United Kingdom.
Abstract:
Uropathogenic strains of Escherichia coli bearing mannose-sensitive (type 1) fimbriae promote a unique pattern of degranulation from human polymorphonuclear leukocytes (PMN). Significant quantities of the primary (1 degree) and tertiary (3 degree) granule markers, neutral protease-myeloperoxidase and N-acetyl-beta-D-glucosaminidase, respectively, were released by PMN in a dose- and time-dependent manner when stimulated by these defined bacterial strains. Organisms bearing mannose-resistant (P) fimbriae promoted release of only the secondary (2 degree) granule marker, vitamin B12-binding protein. When this pattern of degranulation was compared to that produced by PMN in response to a variety of soluble and particulate stimuli, only the calcium ionophore A23187 similarly triggered 1 degree and 3 degree granule marker release. All the other stimuli tested--zymosan, serum-treated and unopsonized; n-formylmethionyl-leucyl-phenylalanine; and phorbol myristate acetate--promoted release of only the 2 degree granule marker. These results demonstrate selectivity of PMN degranulation in response to a number of transmembrane signals. In addition, the capacity of E. coli to promote PMN degranulation is dependent on its phenotypic fimbrial expression, a surface characteristic which correlates significantly with its relative surface hydrophobicity as measured by binding to octyl Sepharose. Those bacteria demonstrating the greatest hydrophobicity were capable of triggering discharge of all three granule marker proteins. Thus, the mannose-sensitive fimbriae of uropathogenic E. coli may contribute significantly to their potential pathophysiologic role in renal scarring.
Insights
Uropathogenic E. coli with mannose-sensitive fimbriae trigger specific human immune cell degranulation. This fimbrial expression and bacterial hydrophobicity are key factors in E. coli
Area of Science:
- Immunology
- Microbiology
- Cell Biology
Background:
- Polymorphonuclear leukocytes (PMN) are crucial immune cells involved in host defense.
- Uropathogenic Escherichia coli (E. coli) employ fimbriae for adhesion and virulence.
- PMN degranulation releases antimicrobial substances and inflammatory mediators.
Purpose of the Study:
- To investigate the specific patterns of human PMN degranulation induced by E. coli strains with different fimbrial types.
- To compare E. coli-induced degranulation with responses to other known PMN stimuli.
- To determine the role of bacterial surface characteristics, such as fimbriae and hydrophobicity, in modulating PMN activation.
Main Methods:
- Stimulation of human PMN with defined uropathogenic E. coli strains expressing mannose-sensitive (type 1) or mannose-resistant (P) fimbriae.
- Measurement of specific granule markers released from PMN: neutral protease-myeloperoxidase (primary), vitamin B12-binding protein (secondary), and N-acetyl-beta-D-glucosaminidase (tertiary).
- Comparison of E. coli-induced degranulation patterns with those induced by calcium ionophore A23187, zymosan, and N-formylmethionyl-leucyl-phenylalanine (fMLP).
- Assessment of bacterial surface hydrophobicity using octyl Sepharose binding.
Main Results:
- Mannose-sensitive fimbriae of E. coli induced release of primary and tertiary granule markers from PMN in a dose- and time-dependent manner.
- E. coli with mannose-resistant fimbriae promoted release of only secondary granule markers.
- Calcium ionophore A23187 mimicked the degranulation pattern of mannose-sensitive fimbriae, while other stimuli (zymosan, fMLP) released only secondary markers.
- Bacterial hydrophobicity correlated with the ability to trigger degranulation, with highly hydrophobic bacteria releasing all three granule markers.
Conclusions:
- PMN degranulation exhibits selectivity in response to different transmembrane signals, including bacterial surface structures.
- The type of fimbriae expressed by uropathogenic E. coli significantly influences the pattern of PMN degranulation.
- Bacterial surface hydrophobicity is a critical factor in E. coli's capacity to activate PMN degranulation.
- Mannose-sensitive fimbriae may play a substantial role in the pathogenesis of E. coli-induced renal scarring through modulation of PMN responses.
