Immunohistochemistry

Last updated: Wednesday, 17, March, 2004

Item	Process
Specimen	Requests for immunohistochemical investigations should be discussed with laboratory staff. Fresh or formalin fixed tissue biopsies may be suitable.
Method	The development of a broad range of antibodies that are applicable to formalin-fixed tissue has dramatically reduced the necessity for fresh tissue for immunohistochemical examination. In many cases tissues are pretreated with wet heat for antigen retrieval. Tissue sections or cell smears are incubated with monoclonal or polyclonal antibodies; bound antibody is detected with an immunoenzyme technique (eg, peroxidase or alkaline phosphatase) and tissue/cells visualised by light microscopy.
Application	Immunohistochemistry permits the determination of the cellular origin of poorly differentiated tumours and has a wide range of applications in diagnostic pathology. Some applications are: the determination of the cellular origin of poorly differentiated tumours; the classification of lymphomas and leukaemias; the detection of micrometastases in tissue; the identification and qualitative estimation of hormone receptors and prognostic markers in tumours; the evaluation of cell cycle activity; and the detection of viral and other infective agent antigens eg, CMV, herpes, legionella.
Interpretation	Positive staining indicates expression of the relevant antigen. The report will detail the immunoexpression of the tissue with an interpretative comment from the pathologist. See also Cell immunophenotyping and Lymphocyte typing.
Reference	Suster S et al eds. Semin Diagn Pathol 2000; 17: 169-256. Leong ASY et al. Manual of diagnostic antibodies for immunohistology. 2nd ed. Greenwich Medical Media 2003.