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Chemiluminescence of human polymorphonuclear leucocytes after stimulation with whole cells and cell-wall components
L Martínez-Martínez1, C P Timmerman, A Fleer
1Eijkman-Winkler Laboratory of Medical Microbiology, University of Utrecht, The Netherlands.
Abstract:
The purpose of this study was to define cell-wall components of Staphylococcus epidermidis responsible for activation of human polymorphonuclear leucocytes (PMNL). Metabolic activation of PMNL was determined by chemiluminescence (CL). Purified peptidoglycan (PG) induced a concentration-dependent metabolic burst in PMNL. The minimal concentration needed for CL induction was 1 microgram/ml. Comparison between different S. epidermidis strains showed variation in the capacity to induce CL in PMNL. Purified PG induced a higher CL response in PMNL than its intact parent strain; this effect was found in all S. epidermidis strains. Lipoteichoic acid (LTA), PG stem peptide and muramyldipeptide (MDP) did not induce CL; teichoic acid induced a CL response only at very high concentrations. No differences in CL inducing capacity were found between PG, crude cell walls, and purified cell walls of S. epidermidis. Sonication of PG strongly diminished CL-inducing capacity. PG treatment with mutanolysin immediately resulted in decreased CL-inducing capacity. Treatment of PG with S. aureus lytic enzyme (SALE) 10 micrograms/ml for up to 15 min enhanced the CL response to PMNL; a similar increase in CL was induced by PG treated with SALE at 1 microgram/ml for up to 120 min. Beyond these times, a continuous decrease in PG-induced CL was observed. In conclusion, PG was found to be the major cell-wall component of S. epidermidis involved in CL induction. Moreover, a minimal fragment size or a specific tertiary structure of PG, or both, is required for metabolic activation of PMNL.
Insights
Staphylococcus epidermidis peptidoglycan (PG) is the main cell-wall component that activates human polymorphonuclear leucocytes (PMNL) via chemiluminescence (CL). Optimal PG fragment size or structure is essential for this immune cell activation.
Area of Science:
- Immunology
- Microbiology
- Biochemistry
Background:
- Staphylococcus epidermidis is a common bacterium.
- Understanding bacterial cell-wall components is crucial for immune response studies.
Purpose of the Study:
- To identify Staphylococcus epidermidis cell-wall components that activate human polymorphonuclear leucocytes (PMNL).
- To investigate the role of peptidoglycan (PG) in this activation process.
Main Methods:
- Metabolic activation of PMNL was measured using chemiluminescence (CL).
- Purified bacterial components including PG, lipoteichoic acid (LTA), and teichoic acid were tested.
- PG was subjected to enzymatic and physical treatments (sonication, mutanolysin, S. aureus lytic enzyme).
Main Results:
- Purified PG induced a concentration-dependent CL response in PMNL, with minimal effective concentration at 1 microgram/ml.
- PG demonstrated higher CL induction capacity than the intact S. epidermidis parent strain.
- LTA, PG stem peptide, and muramyldipeptide did not induce CL; teichoic acid required very high concentrations.
- Sonication and mutanolysin treatment reduced PG's CL-inducing capacity, while S. aureus lytic enzyme (SALE) treatment initially enhanced it.
Conclusions:
- Peptidoglycan (PG) is the primary Staphylococcus epidermidis cell-wall component responsible for inducing chemiluminescence (CL) in PMNL.
- A specific fragment size or tertiary structure of PG, or both, is necessary for the metabolic activation of PMNL.