Designed for detecting common mouse/rabbit-derived primary antibodies, the kit includes an inhibitor to block endogenous peroxidase in tissue sections. The primary antibody selectively binds to the target antigen, forming an antigen-antibody complex. Following primary antibody application, the reagent reduces non-specific binding and improves affinity. The ultra-sensitive enzyme-labeled anti-mouse/rabbit IgG polymer (with HRP) recognizes the primary antibody in the complex. DAB Solution A and B are mixed to prepare the chromogenic solution, which HRP catalyzes to produce brown staining at the antigen location. An enhancer amplifies the brown signal, while hematoxylin provides nuclear counterstaining.