Modification of the protein A-gold immunocytochemical technique for the enhancement of its efficiency.

A modification in the protein A-gold immunocytochemical technique has been introduced for amplification of the labeling. This modification consists of performing additional incubation steps with an anti-protein A antibody and the protein A-gold complex. The original antigen-antibody-protein A-gold complex was further incubated with an antibody directed against protein A and then, in a fourth step, again with protein A-gold. This multiple-step protocol results in significant enhancement of the original signal. The modified technique can be applied to either light or electron microscopy protein A-gold immunocytochemistry. The advantage of such an approach is double: it allows for either amplification of the labeling when the original signal is of low intensity or use of highly diluted antibody solutions. The modification introduced was thus found to significantly enhance the efficiency of the technique.