An overview of immunohistochemistry: Evidence and personal experience.

Immunohistochemistry is a tissue-based technique that enables in situ visualization of specific molecules, most commonly proteins or peptides, within preserved cellular and tissue architecture through antigen-antibody specificity. By using labeled antibodies, immunohistochemistry allows spatially resolved and cell type-specific detection of target molecules and maintains the morphological context, thereby providing both localization and relative expression information at the light or electron microscopy level. Owing to this integrative capacity, immunohistochemistry has become an essential tool in biological research and diagnostic pathology for characterizing molecular distribution and tissue organization across animal and plant systems. The detection techniques based on fluorescence and enzymes (chromogenic) are compared in terms of their repeatability, multiplexing capability, sensitivity, and specificity. With a focus on protocol standardization and methodological rigor, important procedural processes are covered, including fixation, antigen extraction, antibody optimization, signal detection, and quality control. Additionally, the immunohistochemistry technique remains essential for locating and identifying immunogenic substances in a variety of biological settings. Therefore, drawing on more than two decades of laboratory experience, this narrative review summarizes the history of the immunohistochemistry assay, its underlying principles and procedures, common immunohistochemistry protocol, methodological process, essential reagents, infrastructure, and best-practice principles required for the establishment and optimization of a high-quality immunohistochemistry laboratory.