Carbon-based immunocytochemistry. A new approach to the immunostaining of epoxy-resin-embedded material.

A carbon-based immunocytochemistry (CarBIC) method, whereby the epoxy resin is completely removed from a section prior to immunocytochemistry (IC), is described. The resulting absence of embedding medium allows for an optimal access of both primary antibodies and marker systems to structures at various levels throughout the depth of the section. A carbon film evaporated onto the surface of the section before extraction of the resin forms a base to which the section adheres and maintains structural integrity during subsequent processing. The conventional and accepted electron microscopical (EM) appearance for epoxy-resin-embedded material is regained by re-embedding in Epon before contrasting in the normal manner. The technique is demonstrated using human cytomegalovirus (HCMV)-infected human fibroblasts. HCMV+ serum is the source of primary antibodies and 10-nm protein A-gold (pA-G10) together with rabbit anti-human IgG + IgM is the marker for IC.