Antigen Retrieval for Immunohistochemical Reactions in Routinely Processed Paraffin Sections

Immunohistochemistry is an essential adjunct of modern diagnostic pathology. In the majority of cases, pathological tissue samples are fixed in formal dehyde and embedded in paraffin wax for examination of microscopic morphology. A major limitation of routinely processed tissues for immunohistochemistry is that many potentially interesting antigens are altered during tissue fixation and processing. As an alternative, sections of snap-frozen tissues can be used to detect most of these antigens. Nevertheless, paraffin sections offer well-preserved tissue architecture and cytomorphology superior to that obtained in frozen sections and thus allow more accurate antigen localization. Furthermore, paraffin-embedded tissues represent an invaluable source of human tissues, easily accessible for retrospective studies back decades. Thus, for diagnostic and research purposes, paraffin sections are preferred for immunohistochemical analysis by most laboratories.