Immunolabeling with the protein A-gold technique: an overview.

The protein A-gold technique is a postembedding immunolabeling method that permits light- and electron-microscopic localization of intracellular antigens on tissue sections with high sensitivity and resolution. The article reviews practical aspects of tissue fixation and embedding protocols as well as methodologic aspects of the protein A-gold technique; careful control of these interrelated factors is the prerequisite for successful application. The technique is demonstrated by a few selected examples of application in basic research and in applied medical research. The protein A-gold technique provides a good alternative to existing techniques for immunolabeling in diagnostic pathology.