DAB. According to the query on the China Public Education Network, horseradish peroxidase (HRP is the most commonly used), and the substrates are TMB (the most commonly used), DAB (histochemistry substrate), etc. There are many detection methods in clinical immunology testing, the most important of which is immunolabeling technology. Immunolabeling technology refers to the antigen-antibody reaction using fluorescein, enzymes, radioactive isotopes or electron-dense substances to label antigens or antibodies.