Demonstration of a chemotactic factor receptor on macrophages.

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.