Light microscopical detection of antigens and lectin binding sites with gold-labelled reagents on semi-thin Lowicryl K4M sections: usefulness of the photochemical silver reaction for signal amplification.

In the present study, we have investigated the applicability of semi-thin sections from low temperature Lowicryl K4M-embedded tissues for cytochemical labelling with protein A-gold and lectin-gold complexes. In order to ensure the best possible signal-to-noise ratio antibodies, protein A-gold and lectin-gold were applied in concentrations used for labelling at the electron microscope level. Furthermore, due to the lack of an appropriate chemical procedure for resin removal, untreated semi-thin sections were incubated. Under such conditions, semi-thin sections displayed either no visible staining or only a faint incomplete staining. However, following photochemical silver reaction, the latent or faint incomplete staining was rendered visible in most cases. It is concluded that the same block of Lowicryl K4M-embedded tissue and the same labelling reagents can be used for both light and electron microscopical cytochemical studies. At the light microscopical level, a high degree of structural and specific staining information is obtained. The reactivity of cellular components with antibodies or lectins is preserved even after years of storage of the blocks or slides containing semi-thin sections.