Immunoperoxidase methods: increased efficiency using fluorescence microscopy for 3,3-diaminobenzidine (DAB) stained semithin sections.

When semithin sections stained by immunoperoxidase-DAB methods are exposed to ultraviolet light in a fluorescence microscope, immunoreactive cells develop a strong yellowish fluorescence within 2-4 min. This property offers the possibility of visualizing even reaction products which can barely be identified by other microscopical techniques. Thus the efficiency of immunoperoxidase methods is greatly enhanced. Moreover the histochemical proof of endogenous peroxide active enzymes visualized with DAB as substrate may also be facilitated using fluorescence microscopy.