Immunohistochemistry: A Valuable Tool in Diagnosis
Histopathological examination of tissues remains one of the most reliable and definitive diagnostic procedures in medical science. However, traditional staining techniques used in histopathology often lack specificity. Immunohistochemistry (IHC) helps overcome this limitation by allowing visualization of specific antigens in tissues through the use of labeled antibodies. IHC has revolutionized research and clinical practice by providing precise information that assists pathologists make accurate diagnoses. This article aims to provide an overview of IHC and discuss its importance and applications in diagnosis.
What is Immunohistochemistry?
Immunohistochemistry is an immunohistological technique that utilizes the principle of antibodies binding specifically to antigens in biological tissues. In IHC, thin sections of tissue specimens are reacted with known antibodies that are tagged or conjugated with enzymes or fluorescent dyes. These primary antibodies identify cellular proteins in situ within a morphologic context. The antibodies are directed against antigens – substances that can stimulate an immune response in the body. The antibodies bind to their specific antigens present in the tissues, and this binding can be visualized through enzymatic reactions or fluorescence microscopy after substrate addition or exposure to light. The antibodies highlight the precise location of targeted cellular proteins, allowing pathologists to draw definitive conclusions regarding the presence or absence of biomarkers in tissues.
Applications of IHC
IHC finds widespread use in research and clinical pathology laboratories. Some major applications of IHC include:
– Diagnosis of cancers: IHC helps classify tumors according to cellular markers and aids in cancer subtyping. For example, estrogen receptor status in breast cancer evaluated by IHC guides treatment options.
– Diagnosis of infectious diseases: IHC assists in diagnosis of conditions like tuberculosis, fungi, parasites, and human papilloma virus infections.
– Diagnosis of autoimmune and inflammatory diseases: IHC plays a crucial role in identifying cells involved in diseases like rheumatoid arthritis, systemic lupus erythematosus, multiple sclerosis, etc.
– Localization of hormones and receptors: IHC precisely determines the distribution and levels of hormones, growth factors and their receptors in normal and diseased tissues.
– Forensic pathology: IHC antibodies help resolve legal issues by confirming tissue or cell types in biological specimens of forensic interest.
Benefits of IHC
IHC confers several important benefits over conventional histological techniques:
Specificity: IHC allows visualization of specific molecular targets in situ, which greatly enhances diagnostic specificity compared to routine H&E staining.
Sensitivity: Minute amounts of antigens can be detected by IHC, allowing detection of biomarkers even in small biopsy specimens.
Multiplexing: Multiple antigens can be identified simultaneously in the same tissue section by using different colored substrates or fluorochromes, increasing information yield.
Archival tissue use: IHC can be performed on formalin-fixed paraffin-embedded archival tissues, allowing retrospective studies and re-evaluation of older cases.
Morphologic correlation: Identifying cellular markers through IHC in the context of tissue architecture aids precise morphological correlation for diagnostic accuracy.
Limitations of IHC
While IHC has revolutionized diagnostics, it also has certain limitations:
Subject to pre-analytical variables: Tissue fixation and processing methods can affect antigenicity and produce false negatives.
Antibody specificity and validation: Reliability depends on antibody specificity which needs to be carefully validated for each target.
Subjective interpretation: Visual assessment leaves room for inter-observer variation; quantitative imaging analysis addresses this to some extent.
Specialized expertise required: Accurate interpretation demands immunopathology expertise in correlating IHC, histology and clinical findings.
Time consuming: IHC procedure, from antigen retrieval to analysis, takes 1-2 days while H&E gives rapid results.
In summary, immunohistochemistry is a powerful technique that augments classical histopathology by enabling visualization of biomarkers within their cellular context. With careful optimization and correlation with clinical and histological findings, IHC assists pathologists deliver precise diagnoses, aiding clinical decision making. As antibodies and methodology continue to improve, IHC will likely play an ever increasing role in research and application in various fields of pathology.
*Note:
- Source: Coherent Market Insights, Public sources, Desk research
- We have leveraged AI tools to mine information and compile it