A debated and yet unanswered question, in regard to polarization and directed movement of phagocytic cells, concerns the distribution of chemoattractant receptors during cell locomotion1. We have therefore studied the instantaneous distribution of N-formyl-peptide receptors on living neutrophils. Using a fluorescent N-formyl-peptide receptor antagonist, tert-butyloxycarbonyl-Phe(D)-Leu-Phe(D)-Leu-Phe-OH (Boc-FLFLF), and a fluorescent receptor agonist, formyl-Nle-Leu-Phe-Nle-Tyr-Lys (fnLLFnLYK), the localization of the chemoattractant receptors could be followed during random migratio2. Neutrophils were adhered to plasma-coated coverslips. A Nomarski differential interference contrast (DIC)- image was taken, and rapidly followed by a fluorescence-image captured with a water-cooled, slow-scan CCD-camera. Then a second DIC-image was directly recorded to reveal the direction of cell movement.

Using fnLLFnLYK we observed that the distribution of N-formyl-peptide receptors was clearly heterogeneous as shown in figure. Fluorescence was concentrated mainly at the rear and front of elongated locomoting cells, leaving the cell body almost non-fluorescent.