Histopathology involves diagnosing and studying tissue diseases by examining tissues or cells under a microscope. Hematoxylin and Eosin staining, widely used in histopathology, aids in microscopic visualization for identifying infectious agents, particularly when cultures cannot be obtained or the agent is slow-growing or fastidious1. This staining technique is essential for distinguishing cell and tissue types, offering crucial information about cellular patterns, shapes, and structures2. However, challenges arise from the similar appearances of diseases and cells, prompting the emergence of Immunohistochemistry (IHC) as an important technique3.

IHC stands out as the most common immunostaining technique, amalgamating principles from histology, immunology, and biochemistry. It relies on monoclonal and polyclonal antibodies to detect specific antigens or proteins within tissue samples4, offering a unique advantage over other molecular biology techniques like western blotting or enzyme-linked immunosorbent assay (ELISA). Unlike these methods, IHC not only estimates protein expression levels but precisely locates target proteins in tissue without digestion, using a standard light microscope without the need for specialized equipment such as mercury lamps, dichroic mirrors, or filters5.

IHC is a highly specific and sensitive diagnostic method for diagnosing neoplastic diseases, infectious diseases, and neurodegenerative diseases. It is used in drug development to assess drug efficacy by detecting changes in disease targets. IHC provides valuable insights into morphology, localization, and distribution of specific antigens in tissues4. Cost-effective, equipment-friendly, and generally accurate, IHC's diverse applications underscore its significance6. The purpose of this review was to provide a comprehensive and up-to-date overview of immunohistochemistry, encompassing its fundamental techniques, diverse applications in pathology and research, recent technological advancements and future perspectives.