SURFACE EXPRESSION AND DISTRIBUTION OF FC RECEPTOR-III (CD16 MOLECULE) ON HUMAN NATURAL-KILLER-CELLS AND POLYMORPHONUCLEAR NEUTROPHILS

Human natural killer cells and polymorphonuclear neutrophils constitut ively express the low-affinity IgG Fc receptor (Fc gamma RIII, CD16 mo lecule). To investigate cell surface morphology, antigenic receptor de nsity, and topographical distribution of Fc gamma RIII on the plasma m embrane of natural killer cells and polymorphonuclear neutrophils, con ventional scanning electron microscopy (SEM), flow cytometry, and immu noscanning electron microscopy were used. Fc gamma RIII was detected w ith an indirect immunogold labeling procedure, and receptors were visu alized in the backscattered and secondary electron imaging mode of SEM . Natural killer cells showed a cell surface morphology compatible wit h lymphocytic differentiation characterized by microvilli and microrid ges. Polymorphonuclear neutrophils showed surface features characteriz ed by ridges with folds and scattered short microvilli. Natural killer cells displayed a lower cell labeling density, whereas polymorphonucl ear neutrophils showed a high level of expression of Fc gamma RIII on the plasma membrane by quantitative analysis with SEM in the backscatt ered electron imaging mode. Flow cytometry analysis confirmed these fi ndings. Analysis of the topographical distribution of Fc gamma RIII an tigenic receptor sites by SEM in the backscattered and secondary elect ron imaging modes showed that Fc gamma RIII on natural killer cells ar e randomly distributed, whereas Fc gamma RIII are located on ridges an d folds of the plasma membrane of polymorphonuclear neutrophils. These observations suggest that natural killer cells and polymorphonuclear neutrophils differ in their levels of expression and topographic distr ibution of Fc gamma RIII on the plasma membrane. This different spatia l distribution of Fc gamma RIII would provide morphological evidence o f certain cellular functions mediated by natural killer cells and poly morphonuclear neutrophils. (C) 1994 Wiley-Liss, Inc.