The most commonly used enzymes in chromogenic multiplexing are horseradish peroxidase (HRP) and alkaline phosphatase (AP). Corresponding chromogens include 3,3'-diaminobenzidine (DAB) for HRP, which produces a brown precipitate, and Fast Red or BCIP/NBT for AP, which produce red and blue/purple precipitates, respectively. These color distinctions facilitate the identification of multiple antigens within the same tissue section.
