Immunologic observations in canine interstitial nephritis.

Immunofluorescence studies in cases of chronic interstitial nephritis (CIN) in the dog demonstrated deposition of canine IgC and C'3 in the thickened capillary walls of the glomeruli and in the mesangium. Eluates obtained from the nephritic kidneys contained antibodies of IgG type and reacted with autologous or homologous nephritic kidneys but not with normal kidneys or with any normal canine tissue. The staining pattern of fluorescein-conjugated eluates was similar to that obtained with anti-canine IgG or anti-canine C'3. The eluates did not contain leptospiral antibodies. The findings indicate that complement-fixing immune complexes are deposited in the damaged glomeruli in CIN. The nature of the antigen involved in these complexes is unknown, but it does not seem to be a component of normal canine tissue and could thus be viral or bacterial.