Immunofluorescence of deparaffinized, trypsin-treated renal tissues. Preservation of antigens as an adjunct to diagnosis of disease.

The present study compares formalin-fixed, deparaffinized and trypsin-treated (DTT) renal tissue sections with frozen sections for detecting immune complex deposition. Both DTT and frozen sections from 52 renal biopsies were stained directly with fluorescein isothiocyanate-conjugated antihuman IgG, IgM, IgA, fibrinogen, and C3. DTT sections alone were stained indirectly for C3 using a double conjugate technique. Antigen presence or absence on DTT section was accurately detected in 90 per cent of biopsies for immunoglobulins and fibrinogen and in 75 per cent for C3 when compared to frozen section. Furthermore, antigen deposition was found in 21 per cent of biopsies only on DTT sections (usually because frozen tissue lacked glomeruli). Frozen sections alone were treated with reagents of the fixation-embedding process and directly stained for IgM and C3 to determine antigen stability. Alkaline or neutral formalin pH helped maximize antigen preservation. DTT sections are a valuable tissue source for adjunctive diagnosis of renal disease.