Acquisition of formyl peptide receptors during normal human myeloid differentiation

By using a newly developed immune rosetting technique to isolate highly purified populations of myeloid precursor cells from normal human bone marrow and then inducing their differentiation with granulocyte and macrophage colony-stimulating factors (G/M-CSFs) in vitro, we studied the surface expression of chemotactic peptide receptors as the cells matured from the stage of the myeloblast to that of the mature, segmented neutrophil. We used ethylene glycol bis(succinimidyl succinate) to link N-formyl-Nle-Leu-Phe-Nle-[125I]iodo-Tyr-Lys to chemotactic peptide receptors on the surface of myeloid cells at sequential stages of maturation and then determined the density of receptor-radioligand complexes by autoradiography after sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). Specific, saturable formyl peptide receptors were not detectable at the level of the myeloblast but gradually emerged through progressive stages of neutrophil maturation. The specific receptors for formyl peptide that appeared during cellular maturation had a mol wt of 55 to 70 kiloDalton (kD), corresponding to those present on the surface of peripheral blood neutrophils, and binding of the radioligand was highly specific in that it was completely inhibited by a 1,000-fold excess of F-Met Leu Phe. These data correlate with and provide insight into our recent observation that F-Met Leu Phe-induced membrane depolarization and transient increases in cytosolic free calcium are gradually acquired as neutrophils mature. This report represents to our knowledge the first description of the maturational development of chemotactic peptide receptor expression in normal human myeloid cells.