BIOTINYL-TYRAMIDE - A NOVEL-APPROACH FOR ELECTRON-MICROSCOPIC IMMUNOCYTOCHEMISTRY

The biotinyl-tyramide protocol recently introduced for sensitive light microscopic immunocytochemistry was applied to electron microscopy an d revealed various tissue antigens with high resolution. The protocol consists of an indirect method in which thin tissue sections are incub ated successively within a specific primary antibody, followed by a bi otinylated secondary antibody, streptavidin-HRP, and then finally with biotinyl-tyramide. The reaction product appears as a dense filamentou s material that is deposited over particular cellular compartments. Th e labeling obtained for the antigens tested, amylase and heat-shock pr otein 70 in pancreatic acinar cells, insulin in pancreatic beta-cells, and carbamoyl phosphate synthetase and catalase in liver tissue, was found to be highly specific, with the labeling for each antigen confin ed to its particular cellular compartment. Background levels and nonsp ecific deposition of the staining were negligible. The use of biotinyl -tyramide therefore appears to be an alternative sensitive technique f or immunoelectron microscopy.