Immunogold labeling for transmission electron microscopy: applications in cell and molecular biology.

Since its introduction as an electrondense marker for electron microscopy in 1971, colloidal and recently also clustered gold have become the markers of choice for the in situ detection of a wide number of cellular and extracellular molecules by transmission electron microscopy (TEM). In this chapter we briefly review the basic post-embedding immunogold- (IGS) and immunogold-silver staining (IGSS) methodology, and then discuss some more recent applications based on the combination of colloidal gold immunocytochemistry (ICC) with enzyme histochemistry, tracing techniques, and transferase-immunogold labeling procedures for use in cell and molecular biology. A number of publications appeared in the past few years in which the basic IGS methods have been extensively reviewed. In this chapter, we will focus our attention on the more recent exploitations of the technique with particular emphasis on applications in cell and molecular biology. Since our research interest has always been devoted to the study of the central nervous system (CNS), the examples of application described here will mainly be related to analysis of central neurons. Nevertheless, we are confident that the protocols discussed in this chapter will be helpful also to the general biologist and in clinical research. A brief summary of the state of the art will help to put our work in perspective. Readers are referred to the existing literature for a more detailed discussion of primary fixation and for comparison between post-embedding and pre-embedding procedures.