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Demonstration of a chemotactic factor receptor on macrophages
Abstract:
Certain synthetic N-formylated peptides are potent chemotactic agents for phagocytic cells. We have identified a specific, high affinity receptor for the chemotactic peptide fMet-Leu-[3H]Phe on inflammatory as well as on resident guinea pig peritoneal macrophages. The receptor on inflammatory macrophages has an equilibrium dissociation constant (KD) of 11 nM at room temperature, and there are approximately 10,000 binding sites per cell. The receptor on resident peritoneal macrophages has a KD of 7 nM with approximately 12,000 sites per cell. The increased chemotactic responsiveness of inflammatory macrophages as compared to resident macrophages is probably not due to differences in the fMet-Leu-[3h]phe receptor since the number of binding sites per cell and the KD are quite similar. The specificity of the binding site on both cell types for a series of N-formylated peptides correlates well with the ability of the peptides to initiate macrophage chemotaxis. These studies suggest that the chemotactic response of guinea pig peritoneal macrophages to N-formylated peptides is initiated by the binding of the peptides to a specific cell-surface receptor.
Insights
Synthetic N-formylated peptides attract phagocytic cells. Researchers identified a specific receptor for chemotactic peptide fMet-Leu-[3H]Phe on guinea pig macrophages, suggesting this receptor initiates the chemotactic response.
Area of Science:
- Immunology
- Cell Biology
- Biochemistry
Background:
- N-formylated peptides are potent chemoattractants for phagocytic cells.
- Macrophages play a crucial role in the inflammatory response.
Purpose of the Study:
- To identify and characterize the receptor for chemotactic peptides on guinea pig peritoneal macrophages.
- To investigate the role of this receptor in macrophage chemotaxis.
Main Methods:
- Radioligand binding assays using fMet-Leu-[3H]Phe.
- Characterization of receptor affinity (KD) and density on inflammatory and resident macrophages.
- Testing the specificity of peptide binding and its correlation with chemotaxis.
Main Results:
- A specific, high-affinity receptor for fMet-Leu-[3H]Phe was identified on both inflammatory and resident guinea pig peritoneal macrophages.
- Receptor affinity (KD) and density were similar on both cell types (KD of 7-11 nM, ~10,000-12,000 sites/cell).
- Peptide binding specificity correlated with chemotactic activity, suggesting a functional role.
Conclusions:
- The chemotactic response of guinea pig peritoneal macrophages to N-formylated peptides is mediated by a specific cell-surface receptor.
- Differences in chemotactic responsiveness between inflammatory and resident macrophages are likely not due to variations in this specific receptor's properties.