Antigen Retrieval Technique: A Novel Approach to Immunohistochemistry on Routinely Processed Tissue Sections

The antigen retrieval (AR) technique is a non-enzymatic antigen unmasking method that is utilized prior to immunohistochemical staining of formalin-fixed, paraffin-, celloidin- or plastic-embedded tissue sections. Two variations exist; the first, based on high-temperature heating, is applicable to formalin-fixed, paraffin-embedded sections; the second is a non-heating method that involves immersing the tissue section in an AR solution, such as a NaOH-methanol solution, and is suited to celloidin-embedded tissues. As formalin is the most common fixative used in morphology, the heat-induced AR technique has emerged as a very important approach to the immunohistochemistry of routinely processed tissue sections. Since AR was developed in 1991, there have been more than two hundred articles from all over the world demonstrating the value of AR for routine immunohistochemistry. More than 200 antibodies have been tested, yielding excellent immunohistochemical staining using the AR technique on routine tissue sections in almost all instances. This article reviews the basic principles of the method and describes the application, development and standardization of the AR technique as a basis for establishing current standards of practice and as a foundation for further studies.