Detection of immune deposits in glomeruli: a comparative study of paraffin-embedded, enzyme-treated sections and cryostat sections as substrates in immunofluorescence.

Paraffin-embedded tissue can be used as substrate for immunohistochemistry after enzymatic treatment with proteases. The sensitivity of immunofluorescence on enzyme-treated paraffin sections and on unfixed cryostat sections is compared in this study. Pepsin was more efficient by weight than trypsin in restoring the antigenicity of immune deposits. Increased fluorescence intensity was obtained up to a pepsin concentration of 0.4%. Intensity was further increased when pepsin treated sections were treated with trypsin. Immune deposits were detected in enzyme treated, paraffin sections of kidneys of mice injected with anti-GBM diluted 1/200 or less and in cryostat sections of mice injected with anti-GBM diluted 1/400 or less. This small decrease in sensitivity is considered trivial compared with the advantage gained by the excellent preservation of the tissue.