The ImmPRESS polymerized reporter enzyme staining system uses novel conjugation and micropolymer chemistries to create a highly sensitive, ready-to-use, one-step detection system. This unique micropolymer of highly active enzyme (peroxidase or alkaline phosphatase) is attached to our affinity purified secondary antibodies, producing reagents with outstanding sensitivity and low background. The ImmPRESS-AP Alkaline Phosphatase Polymer Reagent micropolymer technology limits steric interference and provides enhanced accessibility to the target avoiding the disadvantages of other polymer systems that use large dextrans or other macromolecules as backbones. The result is crisp, strong staining of antibody targets, especially nuclear and membrane antigens, and greater sensitivity than conventional alkaline phosphatase antibody conjugates and other alkaline phosphatase polymer systems for immunohistochemistry and other applications.