Usefulness of ethanol-fixation and paraffin-embedding technique for renal biopsy specimens—Application of immunoperoxidase technique

Following the report of Sainte-Marie (J. Histochem. Cytochem. 10: 250-256, 1962), it has been recognized that ethanol-fixed paraffin-embedded tissue material can be used for immunohistochemical demonstration of various intra- and extracellular proteins. In our laboratory, renal biopsy specimens have been prepared by ethanol-fixation and paraffin-embedding technique for simultaneous study on light microscopy and immunohistology. These materials were satisfactorily used for routine stainings on light microscopy. In order to evaluate the reliability of immunohistology on these materials, immunoperoxidase (IP) stainings for several immunoproteins (IgG, IgA, IgM, Clq, C3, and fibrinogen) were carried out on 71 cases. The materials were treated with proteolytic enzyme (Protease type XIV Sigma) before IP stainings. The results of IP were compared with the findings of immunofluorescence (IF) study on fresh frozen sections from the same cases. Sensitivity and specificity of IP method were calculated on the basis of IF method as the standard. The antigenicity of deposits in fixed materials could be preserved for several years after the biopsies, and reproduced by proteolytic treatment. Localization of deposits was much clearer than that in IF, and could be simultaneously studied with the serial sections of light microscopy. The results of IP stainings corresponded with those of IF in 73. 2-81.7% except for IgM and fibrinogen (60.6%, 71.0%, respectively). The sensitivity of IP was 78.7-98.1% for all immunoproteins examined. And specificity was 70. 6-91. 2% except for IgM and fibrinogen (51.8%, 66.7% respectively). In conclusion, ethanol-fixed paraffin-embedded materials are suitable for serial examinations by immunohistological technique as well as by light microscopy, and are useful for retrospective studies.