[Use of paraffin sections for immunofluorescence staining in renal biopsy]

To explore the best method for detecting immunoglobulin, HBsAg and HBcAg in formalin-fixed paraffin-embedded renal biopsy tissues by immunofluorescence (IF).

In the study, 45 cases of renal biopsy were collected, including 20 cases of immunoglobulin A (IgA) nephropathy, 15 cases of membranous nephropathy and 10 cases of membranous type hepatitis B virus associated nephritis. IgG, IgA, HBsAg and HBcAg depositions were evaluated in these cases by IF with different antigen retrieval methods and different periods of antibody incubation time. The results were compared with IF on frozen tissues from the same set of cases to evaluate the methodology.

All the cases were negative with heat-induced epitope retrieval alone. Immunoglobulin, HBsAg and HBcAg were more readily identifiable after digestion with trypsin than with pepsin. IgG and IgA were best visualized after 30 min of digestion with trypsin and 90 min of incubation with primary antibody for IgG and IgA. HBsAg and HBcAg were best visualized after 30 min of incubation with primary antibody and 150 min of incubation with secondary antibody. Comparing immunoglobulins, HBsAg and HBcAg on fresh sections and paraffin sections, their visualizations were almost identical with both techniques although the signal on paraffin sections was slightly weaker than that on fresh theretsections.

Trypsin-digested paraffin sections may be used for diagnosis of renal disease whether there are false negative results.