Humanized antibodies are an improving and rapidly growing class of therapeutics for treatment of human disease. Their efficacy depends highly on specificity and sensitivity for the desired target antigen. Thus, preclinical studies of potential human (and humanized) antibody therapeutics include immunohistochemical (IHC) screening. However, non-specific staining due to endogenous human IgG binding is a technical problem in human antibody detection. The Human-on-Human HRP-Polymer kit delivers a solution to this problem by providing reagents to tag the human primary antibody of interest with digoxigenin and detect it on human tissue with an HRPpolymer system. With this detection system, human antibodies bound to human tissue can be detected with high specificity and sensitivity, while significantly reducing or eliminating background. Additionally, the Human-on-Human HRP-Polymer kit does not require overnight incubation steps, allowing for rapid screening of multiple human primary antibody clones.