Human neutrophil membrane topography: examination of distribution, movement, and regeneration of recognition sites using lectins as probes.

Abstract

We have studied the pattern of membrane binding site redistribution, movement, and reappearance in polarized and nonpolarized human neutrophils using fluorescein and rhodamine-labeled lectins as probes. In suspension, polymorphonuclear leukocytes (PMN) were spherical and displayed a random array of recognition sites for all of the probes. PMN polarized in suspension by 10(-6) M N-formyl-L-methionyl-L-phenylalanine (f-Met-Phe), and PMN attached to substrate accumulated the bound lectin recognition site complex at the uropod (for Con A; 92.0 +/- 0.2% of cells and 91.3 +/- 9.8% of cells, respectively). Glutaraldehyde fixation of neutrophils oriented in a chemotactic gradient prior to lectin addition revealed the innate unbound recognition site array. Unbound Con A recognition sites were clustered at the front of 74.7 +/- 0.8% of cells in a "headlight" pattern, but binding sites for other lectins were distributed randomly around the polarized cell. When bound Con A complexes are swept to the tail of the polarized living PMN, "new" unbound Con A binding sites appear at the front of the cell. Neither cycloheximide nor KCN nor colchicine interferred with new binding site appearance. Cytochalasin B and sodium iodacetate prevented PMN polarization and interfered with appearance of new receptors. This suggests that these fresh sites are uncovered, previously cryptic binding sites rather than newly synthesized structures. Lectin binding site topography and movement are related to the functional state of the PMN. Since both Con A and certain bacteria bind to mannose derivatives, we postulate that the "headlight pattern" and uncovering of fresh binding sites aid the PMN in engulfing organisms as the phagocyte moves forward.