Applications of immunogold and lectin-gold labeling in tumor research and diagnosis

Immunohistochemistry and carbohydrate histochemistry have had an enormous impact on both tumor research and diagnosis. In particular, immunogold labeling has provided significant advantages over classical fluorescence and enzyme-based techniques. In light microscopy, the silver-intensified gold labeling has proven highly sensitive and precise in localization. In electron microscopy, the gold particle marker was a prerequisite for succesful and unequivocal antigen detection in electron-dense cellular structures such as secretory granules. In this review we demonstrate the usefulness of light and electron microscopiaal gold labeling techniques as applied in tumor research and diagnosis. The examples include expression of β-1,6 branches and specific sialoglycoconjugates in colon carcinoma, b-12 carbohydrate epitope in breast carcinoma, polysialic acid in neuroendocrine tumors of lung, adrenal and thyroid, as well as studies on proinsulin to insulin conversion in insulinomas. In addition, practical hints for prevention of background taining, tissue fixation, and silver intensification of gold labeling are given.