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      Paraffin immunofluorescence for detection of immune complexes in renal biopsies: an efficient salvage technique for diagnosis of glomerulonephritis in dogs


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          Renal biopsy is an essential tool for the diagnosis of proteinuric kidney diseases in dogs, and evaluation of immune complexes (IC) by immunofluorescence (IF) of frozen sections (IF-F) is required for the diagnosis of IC-mediated glomerulonephritis (ICGN). However, the use of frozen sections from renal biopsies can have limitations. The aim of this study was to develop a reliable IF method using formalin-fixed and paraffin-embedded (FFPE) sections to detect ICs in dog ICGN.


          Renal biopsy specimens were obtained from dogs with protein-losing nephropathies. FFPE sections were prepared, and eight antigen retrieval pretreatment protocols were performed: digestion with trypsin, microwave (MW) heating in citrate buffer (MW-CB; pH 6.0), MW heating in Tris-EDTA buffer (MW-TEB; pH 9.0), as well as combinations of the above, and a non-treated control.


          A combination of trypsin for 30 min (Try-30) and MW-TEB; pH 9.0 was the most effective antigen retrieval pretreatment, with clear positive signals for IgG, IgA, IgM, and C3 detected by IF-FFPE. Granular signals, an important diagnostic indicator of ICGN, were clearly observed by both IF-F and IF-FFPE after combined pretreatment with Try-30 and MW-TEB, and IgG, IgA, IgM, and C3 signals were almost completely matched in all samples by IF-F and IF-FFPE.


          IF-FFPE with Try-30 and MW-TEB pretreatment is a valuable technique for the diagnosis of renal diseases in dogs. This method could be an efficient tool when standard IF-F cannot be used, or does not provide useful results due to lack of glomeruli in the specimens for IF-F.

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          Immunofluorescence on pronase-digested paraffin sections: a valuable salvage technique for renal biopsies.

          Direct immunofluorescence (IF) on frozen tissue is the method of choice for the study of medical renal diseases. When no glomeruli are available, IF can be performed on the formalin-fixed paraffin-embedded tissue allocated for light microscopy after antigen retrieval with proteases. In this study, the results of IF on frozen tissue (IF-F) and on deparaffinized, pronase-treated tissue (IF-P) were compared in 71 renal biopsies representing 12 major renal diseases. Using IF-P, diagnostic findings were obtained in 100% of cases of lupus nephritis, acute post-infectious glomerulonephritis, cryoglobulinemic glomerulonephritis, fibrillary glomerulonephritis, primary amyloidosis, myeloma cast nephropathy, and light-chain Fanconi syndrome (LCFS), 88% of cases of immunoglobulin (Ig)A nephropathy, 80% of cases of light-chain deposition disease, 60% of cases of membranoproliferative glomerulonephritis type 1, 50% of cases of idiopathic membranous glomerulopathy (MGN) and 20% of cases of anti-glomerular basement membrane (GBM) disease. IF-P was less sensitive than IF-F for the detection of C3 in all disease categories and for the detection of IgG in cases of MGN and anti-GBM disease. The diagnostic kappa light-chain staining was demonstrated in 100% of cases of LCFS by IF-P versus 40% by IF-F. We conclude that IF-P is a valuable salvage immunohistochemical technique for renal biopsies lacking adequate cortical sampling for IF-F, and is superior to IF-F for the diagnosis of LCFS.
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            Paraffin immunofluorescence in the renal pathology laboratory: more than a salvage technique.

            Immunofluorescence studies on paraffin-embedded tissue after Pronase digestion (paraffin immunofluorescence) is used as a salvage technique in renal pathology, when frozen tissue for routine immunofluorescence is inadequate. We have recently found that it is also useful in rare cases in which the immune deposits are 'masked' on routine immunofluorescence, giving false-negative staining by routine immunofluorescence and positive staining by paraffin immunofluorescence. This study aims to evaluate the role of paraffin immunofluorescence in clinical practice with emphasis on its utility to avoid misdiagnosis of cases with masked immune complex deposits. Paraffin immunofluorescence was used in 304 (6.1%) of 4969 native biopsies reviewed from our files. In 207 (68.1%) cases, paraffin immunofluorescence was used as a salvage technique. It was necessary for diagnosis in 24 (11.6%) and had a significant contribution in 63 (30.4%) of these cases. Paraffin immunofluorescence was used to evaluate masked deposits in 97 (31.9%) cases. In 61 (62.9%) of these cases it was used to evaluate masked immune complex glomerular deposits, and in 36 cases (37.1%) it was used to evaluate masked paraproteins. Of the cases where immune complex deposits were sought, paraffin immunofluorescence was necessary for diagnosis in 16 (26.2%) cases and had a significant contribution in 4 (6.6%) cases. Fourteen of the 20 cases with masked deposits had C3 dominant stain by routine immunofluorescence, which could have been misdiagnosed as C3 glomerulopathy. Overall, paraffin immunofluorescence was necessary or had a significant contribution to diagnosis in >1/3 of the cases and is a valuable technique in renal pathology.
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              Immunoperoxidase versus immunofluorescence in the assessment of human renal biopsies.

              For half a century, immunofluorescence (IF) on frozen sections has been the gold standard for immunohistochemical evaluation of renal biopsy specimens. In routine diagnostic immunohistopathologic evaluation, traditional IF has been replaced to a large extent by immunoperoxidase (IP) methods applied to paraffin sections of formaldehyde-fixed tissue. This is caused in part by the practical disadvantages inherent in the IF method, eg, separate tissue specimen and handling, UV microscopy, fading and impermanence of the label-making archiving, and difficult later investigation. Our aim for the present study is to evaluate IP as an alternative to IF in the diagnostic assessment of renal biopsy specimens. Proteolytic antigen retrieval, antibodies effective on deparaffinized sections, a sensitive detection system (Dako EnVision HRP; Dako, Copenhagen, Denmark), and a standardized and rigorously controlled procedure were applied to a series of renal biopsy specimens (n = 81) previously classified by means of light microscopy (LM) and IF. Staining for immunoglobulin G (IgG), IgA, IgM, C1q, and C3c were recorded as positive or negative for IF and IP in paired proportions, presuming that IF was the test standard. Concordant observations were 71% for all (282 of 398 observations), 82% for IgG (65 of 79 observations), and 89% for IgA (72 of 81 observations). The majority of discordant observations (74 of 116 observations) were positive by means of IP, with mesangial deposits of IgM and C1q that were not found by IF. Statistically, there was no significant difference in outcomes between IF and IP for IgG, IgA, and C3c ( P > 0.2). In addition, IP staining allowed simultaneous evaluation of tissue by LM and therefore correlation between tissue structure and immune deposits not readily attained by IF. In the present study, it is documented that for the detection of IgG, IgA, and C3c, IP applied to protease-digested deparaffinized sections of formaldehyde-fixed renal tissue is, with few exceptions, equal to IF on frozen sections. The EnVision HRP method used here is several times more effective in terms of primary antibody dilution than earlier existing IP methods, and because the avidin-biotin system is not involved, very little nonspecific background staining will occur. Discordant observations (116 of 398 observations; 29%) were in the majority (91 of 116 observations) due to positive IP findings of IgM and C1q, which deserve additional investigation.

                Author and article information

                BMC Vet Res
                BMC Vet. Res
                BMC Veterinary Research
                BioMed Central (London )
                1 December 2017
                1 December 2017
                : 13
                ISNI 0000 0001 1167 1801, GRID grid.258333.c, Laboratory of Veterinary Clinical Pathology, Joint Faculty of Veterinary Medicine, , Kagoshima University, ; 1-21-24 Korimoto, Kagoshima, 890-0065 Japan
                © The Author(s). 2017

                Open AccessThis article is distributed under the terms of the Creative Commons Attribution 4.0 International License ( http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver ( http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.

                Funded by: FundRef http://dx.doi.org/10.13039/501100001691, Japan Society for the Promotion of Science;
                Award ID: 16K08056
                Award Recipient :
                Methodology Article
                Custom metadata
                © The Author(s) 2017

                Veterinary medicine
                dog,glomerulonephritis,immune complex,immunofluorescence,paraffin section,renal biopsy


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