ANTIGEN RETRIEVAL FOR ELECTRON-MICROSCOPY USING A MICROWAVE TECHNIQUEFOR EPITHELIAL AND BASAL LAMINA ANTIGENS

The current study extends the principles of the antigen retrieval tech nique for formalin-fixed, paraffin-embedded tissues to transmission el ectron microscopy. Specimens prepared for both routine and immunoultra structural studies were examined for the effects of microwave treatmen t on the immunolabeling of tissue antigens. Specimens of normal rat to ngue mucosa and human oral mucosa were microwaved before immunogold la beling was done using six types of antibody (types I, III, IV, and VI collagen, laminin, and cytokeratin). Sections were cut from tissue blo cks that had been fixed and embedded for either ultrastructural immuno cytochemistry in L.R. White resin or routine electron microscopic morp hology in TAAB resin. Compared with nonmicrowaved sections, microwave- treated, immunolabeled sections of both types of embedded tissues reve aled markedly enhanced gold labeling for type IV collagen in the oral epithelial basal lamina. Moreover, microwave-treated L.R. White sectio ns showed greater label density for type III and VI collagens and for cytokeratin compared with nonmicrowaved sections. There was variable g old labeling for laminin in both TAAB and L.R. White sections with or without microwave pretreatment and no improvement in type I collagen d etection in microwave-treated sections. We concluded that postembeddin g microwave treatment of plastic ultrathin sections on sodium citrate buffer enhances some tissue antigens by increasing the likelihood of r eexposing epitopes encrypted by a fixative-denaturative milieu. This m icrowave technique offers the potential of combining immunocytochemist ry with enhanced exposure of antigenic markers of ultrastructural morp hology in a number of extracellular sites.