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Stimulation of migration of human monocytes by bacterial cell walls and muramyl peptides
Abstract:
Bacterial cell walls, water-soluble fragments of the wall peptidoglycan, N-acetylmuramyl-L-alanyl-D-isoglutamine (MDP), and 6-O-acyl derivatives of MDP were examined for migration-stimulating activity on human peripheral blood monocytes by using a multiwell chemotaxis assembly. Cell walls isolated from 11 bacterial species caused a definite increase in monocyte migration, but the walls of Micrococcus lysodeikticus were scarely active. The migration-enhancing activity of Staphylococcus epidermidis cell walls was retained by a monomer as well as a polymer of disaccharide peptides which were prepared by digestion of the peptidoglycan with enzymes. It was finally revealed that the migration of monocytes was enhanced by MDP. 6-O-Octadecanoyl-MDP, 6-O-(2-tetradecylhexadecanoyl)-MDP, and 6-O-(3-hydroxy-2-docosylhexacosanoyl)-N-acetylmuramyl-L-seryl-D-isoglutamine were active, but to a lesser extent. A checkerboard assay demonstrated that the increased monocyte migration caused by S. epidermidis cell walls was directed toward a positive stimulus (chemotaxis).
Insights
Bacterial cell wall fragments, including N-acetylmuramyl-L-alanyl-D-isoglutamine (MDP), stimulate human monocyte migration. This immune cell activity is crucial for understanding bacterial interactions and potential therapeutic targets.
Area of Science:
- Immunology
- Microbiology
- Cell Biology
Background:
- Bacterial cell walls contain components that can modulate immune responses.
- Monocytes play a critical role in innate and adaptive immunity, including host defense against bacterial infections.
Purpose of the Study:
- To investigate the migration-stimulating activity of bacterial cell walls and their fragments on human peripheral blood monocytes.
- To identify specific bacterial components responsible for enhancing monocyte migration.
Main Methods:
- Utilized a multiwell chemotaxis assembly to assess monocyte migration.
- Examined cell walls from 11 bacterial species, water-soluble peptidoglycan fragments, N-acetylmuramyl-L-alanyl-D-isoglutamine (MDP), and its acyl derivatives.
- Employed enzymatic digestion to prepare monomer and polymer disaccharide peptides.
- Conducted a checkerboard assay to confirm chemotactic activity.
Main Results:
- Cell walls from most tested bacterial species significantly increased monocyte migration.
- N-acetylmuramyl-L-alanyl-D-isoglutamine (MDP) was identified as a key migration-enhancing component.
- Acyl derivatives of MDP also showed activity, though to a lesser extent.
- Enzymatically derived peptides from Staphylococcus epidermidis cell walls retained migration-enhancing properties.
- Checkerboard assay confirmed that the enhanced migration was directed chemotaxis.
Conclusions:
- Bacterial cell wall components, particularly MDP, are potent chemoattractants for human monocytes.
- These findings highlight the immunomodulatory potential of bacterial peptidoglycans and their fragments.
- Understanding these interactions can inform strategies for modulating immune responses in infectious diseases.