POSTEMBEDDING IMMUNOELECTRON MICROSCOPY WITH IMMUNOGOLD-SILVER STAINING (IGSS) IN EPON 812, DURCUPAN ACM AND LR-WHITE RESIN EMBEDDED TISSUES

Intracellular, extracellular, and bacterial antigens were demonstrated ultrastructurally by means of silver enhanced immunogold marker systems (IGSS method). Mild fixation provided a suitable compromise between the ultrastructural and antigenic preservation. The use of small (5 nm) gold-coupled streptavidin on anti-rabbit IgG markers resulted in high sensitivity, which could be further amplified in the latter case by repeating both incubation steps in a double sandwich. However, without the silver enhancement step, the traditional counterstainings obscured the particles, and the ultrastructure was hardly visible on weak tissue staining. The photographic silver reaction allowed good reaction product visualization. In LR-White sections, a doubled silver reaction time was necessary to attain the same particle size as for those in epoxides. LR-White embedding was found to be at least as good as epoxy embedding in preserving immunoreactivity, and in some cases, more effective. The system described is a simple way to achieve reliable results in postembedding ultrastructural antigen detection in routine laboratories.