The principle of ABC detection kits for IHC is based on the affinity of avidin (or streptavidin) for biotin. Indeed, abbreviation ABC stands for Avidin / Biotin Complex.

The multi-species ABC detection kits are designed to detect primary mouse and rat antibodies by immunohistochemistry:

• Biotinylated secondary antibodies to mouse and rat IgG
• Avidin / AP complex (Alkaline Phosphatase)

The kits may or may not contain the blocking and dilution buffers and the substrate depending on the formats. In general, bulk kits (larger volumes) do not include the substrate.

The most commonly used alkaline phosphatase substrates are Fast Red and Permanent Red. These 2 substrates form water-insoluble red precipitates when hydrolysed by alkaline phosphatase (AP). It is for this reason that they are commonly called chromogens. The localization of the target proteins is then carried out by microscopic visualization of the precipitates within the tissue.