Rat primary antibodies on mouse tissues are advantageous because rat secondary detection systems can be used with minimum cross-reactivity to endogenous mouse IgG. Biocare Medical has developed a Rat-on-Mouse horseradish peroxidase (HRP) polymer detection system with minimal cross-reactivity to mouse tissues. It can be used with formalin-fixed paraffin-embedded tissues, floating sections, frozen sections and cell culture preparations. The Rat-on-Mouse HRP-Polymer is comprised of two reagents: A Rat Probe that binds to the rat primary antibody and a Rat-on-Mouse HRP-Polymer that conjugates to the probe. This two-step system has been proven to be 10-20 times more sensitive than conventional conjugated mouse adsorbed anti-rat HRP secondary detection systems. Biocare Medical has novel products to help eliminate persistent mouse IgG. XM Factor is a very potent blocker for eliminating endogenous mouse IgG. By adding 1-2 drops (1 drop equals 33µl) of the XM Factor to 2.5ml of the Rat-on-Mouse Polymer, endogenous mouse IgG will be dramatically reduced and/or completely eliminated. Rodent Block M is a blocking reagent for nonspecific background staining that also reduces endogenous mouse IgG. Rodent Block M is applied prior to the primary antibody for 15-30 minutes. Biocare Medical has also developed Rodent Decloaker, an antigen retrieval solution, which helps reduce and/or eliminate endogenous mouse and rat IgG and non-specific background staining. Temperature dependent protocols can be performed using Biocare’s Decloaking Chamber.