HistostarTM (Ms + Rb) (Immunostaining Reagent, Anti-Mouse and Anti-Rabbit) is the labeled polymer prepared by combining amino acid polymers with peroxidase and goat anti-Mouse Ig and goat anti-Rabbit Ig which are reduced to Fab’. IgG fraction purified from immunized goat serum is digested to prepare F(ab’)2. Antigen-specific F(ab’)2 is affinity-purified with the antigen. Solid-phase absorption is carried out with human serum protein. Peroxidase-labeled amino acid polymer is conjugated to Fab’ obtained by reducing F(ab’)2.