A study of detection and comparison of immunofluorescence on formalin-fixed paraffin-embedded tissue with fresh frozen renal biopsy specimen.

Direct immunofluorescence on the fresh frozen tissue is established way of demonstrating of immunoglobulins and complement deposition in renal biopsies. IF studies can be done on paraffin-fixed tissue (IF-P) and give comparable results to those obtained on frozen tissue for most pathogenic immunoglobulins and immunoglobulin fragments; although, the detection of C3c may be more problematic. In our study, we used proteinase-K method for antigen retrieval. We aimed to detect immunoglobulins and complements in formalin-fixed paraffin-embedded (FFPE) tissue sections from renal biopsies and have comparison of IF staining intensity on FFPE sections with conventional IF on fresh frozen tissue. Based on our results, we conclude that IF-P can serve as salvage technique and has significant diagnostic utility.