Applications of immunocolloids in light microscopy. III. Demonstration of antigenic and lectin-binding sites in semithin resin sections.

Previous studies have demonstrated that antigens or lectin-binding sites can be localized in sections from paraffin-embedded tissues with protein A or lectins bound to colloidal gold or colloidal silver (Roth J: J Histochem Cytochem 30:691, 1982 and 31:547, 1983). In the present study the protein A-gold technique and lectin-gold complexes have been applied to semithin sections (0.5-1.5 micron) of Epon- or low temperature Lowicryl K4M-embedded rat pancreas, kidney and submandibular gland. The results show that an increase in resolution and, therefore, in amount of information can be obtained. The optimal mode of imaging was determined on sections without counterstaining. Bright-field illumination gives the maximum information about the staining signal, while phase-contrast and Nomarski differential interference contrast give predominantly structural and, to a lesser extent, staining information. Polarization epi- and transillumination microscopy is inferior in all aspects. The application of a battery of lectin-gold complexes to rat submandibular gland revealed a specific staining pattern for each lectin in acinar and excretory duct cells.