Immunogold labeling of cell surface antigens: The Scanning Electron Microscope approaches.

Abstract

The scanning electron microscope (SEM) has been used for many years to visualize the distribution of various antigens expressed on cell surfaces. Several markers were used for that purpose, as reviewed by Molday; they were recognized on cell surfaces on the basis of their size and/or shape. However, it is only after colloidal gold particles were demonstrated to be markers of almost universal applicability that the significance of inmuno-SEM in cell biology became evident. The unique properties of the colloidal gold marker can be summarized as follows: it can be prepared in a range of sizes (5 to 40 nm) which accommodates well the resolution of both TEM and SEM; under the light microscope it can be seen as a red stain, or under polarized light epi-illumination; almost all proteins can easily be electrostatically conjugated to it, without noticeable alteration of their biological properties;