Immunoelectron microscopy of human renal biopsies: prerequisites and limitations

The traditional diagnostic approach to immunologically mediated glomerulonephritis is based on the morphological (both in light and electron microscopy) and immunofluorescence examinations of different samples of the same renal biopsy. A major disadvantage of this composite procedure is represented by the inability to precisely correlate the immunocytochemical data with the presence and distribution of electron-dense deposits. Immunoelectron-microscopic techniques could therefore represent a more useful tool for immunomorphological investigations into these glomerulopathies. In order to overcome the significant limitations of preembedding staining procedures, we introduce two postembedding staining techniques (using peroxidase or colloidal gold as markers of the immunoreaction) which result in a precise immunolocalization of immunoglobulins in the dense deposits of glutaraldehyde-fixed, postosmicated and Epon-embedded renal biopsies, while adequately preserving the ultrastructural morphology of the tissue sections.