Determination of a specific receptor for formyl-methionyl-leucyl-phenylalanine on the pulmonary alveolar macrophage and its relationship to chemotaxis and superoxide production

³H-FMLP, a chemotactic peptide that resembles Escherichia coli chemotactic factor, is chemotactic for PAM, binds specifically to a site on the cell, and induces the generation of superoxide radicals by the cell. Scatchard analysis revealed an equilibrium dissociation constant at 26°C of 1.45 x 10^-8M and the presence of 1.7 x 10^-5 receptors per cell. Binding was not inhibited by a partially purified C5a preparation or by the neutrophil-derived CCF but was inhibited by various N-formylated peptides. The order of potency of each peptide to inhibit ³H-FMLP binding was identical to the order of potency of each peptide to induce generation of superoxide by the PAM. Only small amounts of β-glucuronidase activity and no lysozyme were detected in the supernatant after incubation of the cells for 30 min with varying concentrations of FMLP.