Immunocytochemical localization of peroxisomal proteins in human liver and kidney

The sample preparation and immunocytochemical methods for investigating the presence and subcellular localization of peroxisomal proteins (catalase, the three beta-oxidation enzymes, alanine:glyoxylate aminotransferase and a peroxisomal membrane protein) in human liver biopsies are described. We present a protocol for immunolabelling on ultrathin and semithin sections from the same tissue block, with protein A-colloidal gold as a reporter system. For this purpose, the tissue is embedded in Unicryl, a hydrophilic acrylic resin that is cured by ultraviolet illumination at 2 degrees C. The limitations and possibilities of the methods are discussed together with methodological problems. Cryostat sections of prefixed material should be used for the visualization by light microscopy of cytoplasmic catalase. It is emphasized that immunolabelling for catalase in formalin-fixed archival liver samples and in liver autopsy tissue (in the latter also for the peroxisomal beta-oxidation enzymes) permits visualization of peroxisomes; this can be helpful in diagnosing an index case retrospectively.