Mouse IgG3 binding protein (IgG3 BP) conjugated to biotin (B) is a strongly recommended alternative to conventional goat/rabbit anti-mouse IgG secondary antibodies for immunohistochemical (IHC) signal enhancement. Mouse IgG3 binding protein is a highly specific reagent that provides strong signal with minimal background and virtually complete elimination of lot to lot variation associated with conventionally generated secondary antibodies. Mouse IgG3 binding protein (m-IgG3 BP) is suitable for for binding to most, but not all mouse monoclonal IgG3 antibodies; not suitable for use with mouse monoclonal IgG1, IgG2a, IgG2b, IgM, IgA or IgE antibodies. Not cross reactive with human or rat IgG antibodies.