Glomerulonephritis induced by high doses of ovalbumin. Studies by electron microscopy, immunofluorescence and immuno-electron microscopy

Immunoelectron microscopic localization of immune deposits in IgA glomerulonephritis

Renal biopsy specimens obtained from twelve patients with IgA glomerulonephritis (IgA GN) were studied by immunoelectron microscopy (IEM) concomitantly with light microscopy (LM), immunofluorescence microscopy (IF), and electron microscopy (EM). For IEM, we used horseradish peroxidase (HRP)-conjugated antisera to human immunoglobulins (Ig) and to the complement component C3, and a diffusion technique with periodate-lysine-paraformaldehyde (PLP)-fixed tissue-chopper or cryostat sections. Due to well-preserved ultrastructure and good penetration of the antisera in the tissue-chopper sections, a detailed analysis of the distribution of immune material in the glomeruli was possible. In cryostat sections, ice crystal artifacts could not be avoided. The typical features of IgA GN could be reliably confirmed by IEM. Furthermore, IEM revealed the presence of Ig's and C3 in mesangial channels, in the intracellular vacuoles of glomerular cells, and in the electron-lucent areas along the glomerular basement membranes (GBMs). Staining of the mesangial channels indicates that they represent a route for the immune material gaining access into the mesangium. Intracellular vacuoles suggest that the deposited immune material can be partly eliminated through endocytosis by glomerular cells. The presence of Ig's and C3 in the electron-lucent areas supplies an explanation to the discrepancy sometimes observed between a positive finding in IF and a lack of deposits in EM.

Experimental IgA nephropathy in bile duct ligated rats

Polymeric IgA and polymeric IgA-containing immune complexes are transported from blood to bile through hepatocyte-bound secretory component. In order to investigate interruption of this transport and its effect on the glomerulus, Sprague-Dawley rats underwent bile duct ligation. Renal tissue obtained at the time of sacrifice was stained by immunofluorescent techniques with antibodies to IgG, IgM, and IgA, and secretory component (SC) and C3. A progressive selective increase in the staining intensity of the glomerular mesangium was observed for IgA, C3, and SC in bile duct ligated rats. These changes were paralleled by a rise in serum IgA and C3. These findings are consistent with the view that glomerular deposition of IgA, C3, and SC in bile duct ligated rats may result from impairment of normal handling of polymeric IgA and polymeric IgA-containing immune complexes.

Fixation and embedding variables in the immuno-electron microscopic study of rat Heymann nephritis

Fixation and embedding variables were compared in immuno-electron microscopic localization of rat IgG in an autologous immune complex-type nephritis. Specimens from kidney cortex were fixed for 3, 6 or 9 h in the following fixatives made in 0.1 M phosphate buffer at pH 7.4: 4% paraformaldehyde, 2.5% glutaraldehyde, periodate- lysine-paraformaldehyde or modified Karnovsky's fixative. Localization of IgG was performed on tissue sections cut with a tissue chopper, cryostat or sliding microtome, using agarose, Ames O.C.T. Compound or polyethylene glycol respectively as cutting matrixes. The sections were incubated in peroxidase-labelled antirat IgG antiserum (diluted 1:20 with phosphate-buffered saline) for 60 h. Peroxidase activity was then revealed and the sections embedded in Epon. Exact localization of IgG throughout the sections and good ultrastructure were achieved when paraformaldehyde and agarose were used. Periodatelysine-paraformaldehyde proved almost as useful as paraformaldehyde in connection with agarose in respect of peroxidase reaction and ultrastructure. Fixatives containing glutaraldehyde gave a mostly weak and unevenly distributed peroxidase reaction product. In the cryostat sections breaking of the tissue structure could not be avoided. When polyethylene glycol was used as cutting matrix no peroxidase reaction was achieved.