immunohistochemi

Immunohistochemistry, often abbreviated IHC, is a laboratory technique used to detect specific antigens in tissue sections by exploiting the binding of antibodies to their target proteins within preserved cells and tissue architecture. It is widely used in pathology and research to localize proteins in situ and to relate expression to anatomical context.

In a typical IHC workflow, a formalin-fixed, paraffin-embedded tissue section is prepared on a slide, deparaffinized, and rehydrated. Antigen retrieval may be performed to unmask epitopes. After blocking non-specific binding, a primary antibody directed against the antigen is applied, followed by a labeled secondary antibody or an enzyme- or fluorophore-based detection system. Visualization is achieved with chromogenic substrates such as 3,3'-diaminobenzidine (DAB), which yields a brown signal, or with fluorescent dyes for immunofluorescence. The resulting signal indicates the presence and distribution of the target protein.

Interpretation relies on appropriate controls, including known positive and negative tissues, to assess specificity and to distinguish true localization from background staining. Staining is evaluated for its pattern, intensity, and extent, and may be semi-quantified with scoring systems. Common challenges include non-specific staining, cross-reactivity, autofluorescence, and variability from pre-analytical steps.

Advances include automated staining platforms, multiplex immunohistochemistry, and multiplex immunofluorescence, enabling simultaneous detection of multiple antigens. Applications span diagnostic pathology (tumor classification and prognostic markers), infectious disease detection, and basic research into protein expression and tissue localization.