Use of Monoclonal Antibodies in Immunohistochemistry

Immunohistochemistry (IHC) or immunocytochemistry is a method for the localization of specific antigens in tissues or cells using antibody probes. Because it provides detailed and specific information on the expression of cell markers, the IHC technique has wide application in the identification and classification of cell types, with particular value in diagnostic surgical pathology for infectious disease and tumor diagnosis. A milestone in the development of IHC has been reached with its expanding use of routinely processed, paraffin-embedded tissue sections, an achievement made possible by a series of technical accomplishments that include increased sensitivity of detection, monoclonal antibody (MAb) technology, and antigen retrieval methods to recover antigenicity lost during tissue processing. In the past 10 yr, IHC has made a significant impact on diagnostic surgical pathology, becoming one of the most useful auxiliary diagnostic procedures for the visualization of specific antigens in tissue sections and cell smears. In a large proportion of difficult or ambiguous cases of histopathologic diagnosis, IHC can enhance diagnostic accuracy, particularly in the area of neoplastic processes. For example, IHC can provide accurate differentiation of as many as 75% of poorly differentiated or undifferentiated tumors (1 ). The rapid advancement of IHC has also been fueled by the commercial availability of hundreds of MAbs and detection systems, often provided in kit form containing ready-to-use reagents. Despite problems of insufficient quality control and a lack of standardization of many IHC reagents, the IHC technique is now commonly used as a daily adjunct to the traditional staining methods of diagnostic surgical pathology.