Antibodies reacting with the glomerular mesangium. Isolation and immunopathology

Epitope-specific induction of mesangial lesions with proteinuria by a MoAb against mesangial cell surface antigen

A MoAb 1-22-3 (IgG3) was produced in mice immunized with rat glomeruli. A blotting study indicated the antigen molecule recognized by this MoAb has a molecular weight of about 25 kD, which is the same as that of the Thy 1.1 molecule. This MoAb is capable of inducing the morphological changes similar to those induced by anti-thymocyte serum or the anti-Thy 1.1 MoAb, ER4 and massive proteinuria in rats by a single i.v. injection. Proteinuria started immediately after MoAb 1-22-3 injection and peaked on day 5. Reaction products were detected by immunoelectron microscopy in vitro on the limited mesangial cell surface facing endothelial cells and in vivo in partially lysed mesangial cells 30 min after injection. Unlike the proteinuria-inducing MoAb ER4, reactivity of MoAb 1-22-3 was detected neither on endothelial cells, epithelial cells, nor along the glomerular basement membrane in vivo and in vitro. There is a difference in reactivity toward guinea-pig and rabbit materials between MoAb 1-22-3 and the commercial anti-Thy 1.1 MoAb (OX7). The antigenic determinant of MoAb 1-22-3 is concluded to be a new epitope and only the binding of MoAb 1-22-3 to this epitope proved to lead to an abnormal increase of glomerular capillary wall permeability.

Protein aggregates in extracorporally perfused rabbit kidneys

Eighteen rabbit kidneys were perfused ex vivo for 1 h with allogeneic blood, and in 16 a solution of xenogeneic aggregate-free, aggregated or antibody-complexed protein was added to the perfusate 5 min after the start (human immunoglobulins or serum albumin, partly cationized, were used). The kidneys were examined by light and electron microscopy and the human and rabbit immunoglobulin (or albumin) precipitates were detected by direct immunofluorescence and ultrastructural immunohistochemistry. In 13 kidneys the perfusion produced small segmental glomerular endocapillary aggregates of platelets, leukocytes, and granular precipitates reactive with both anti-rabbit and anti-human antibodies. No typical deposits were seen in mesangium or in periphery of glomerular capillaries but rabbit Ig penetrated to the inter- and subepithelial spaces of proximal convoluted tubules. Three kidneys perfused by cationized aggregated human Ig (or by cationized albumin-antialbumin complexes) exhibited a destructive lesion with rapid breakdown of blood flow and massive global endocapillary plugs of similar ultrastructure but with focal endothelial sloughing. Pericapillary granular precipitates of human and rabbit Ig were seen in these kidneys. When the blood with cationized Ig aggregates was used for perfusion of two further kidneys extensive endocapillary aggregates with endothelial damage reappeared but the extracapillary penetration and precipitation were lacking and the blood flow largely improved. Membrane polyanion of podocytes stained by colloidal iron was preserved even in close proximity of cationized complex precipitates. Thus, in the ex-vivo perfusion model the preformed neutral aggregates did not penetrate through the glomerular capillary wall and were not phagocytized by mesangial cells. The cationized aggregates induced rapid circulatory failure with massive platelet clumping and granular pericapillary "humps" ultrastructurally different from the deposits of human and experimental immune complex glomerulonephritis.

Experimental mesangioproliferative glomerulonephritis in rats induced by intravenous administration of anti-thymocyte serum

Focal glomerulonephritis was induced in rats, by a single intravenous injection of anti-Thy-1.1 antibody (ATS). One hour after the administration, the glomeruli of affected rats developed necrotic changes of the mesangial cells while after two hours, mesangiolytic changes appeared. From six days onwards, focal segmental mesangial proliferation which persisted until 30 days, occurred. This is thought to be the first report of experimental nephritis induced by pure anti-mesangial antibody.

Mesangial immune deposits induced in rats by antibodies to fibronectin

Immune deposits in the glomerular mesangium were induced in rats by injection of rabbit antibodies to rat plasma fibronectin (FN). By direct immunofluorescence and electron microscopy, deposits of immunoglobulins were detected in the mesangium of all rats injected with anti-FN IgG but not of control rats injected with normal rabbit IgG. By light microscopy, kidneys obtained 20 days after the antibody injection appeared to be normal. No proteinuria was detected during the experiment. Tissue uptake studies combined with direct immunofluorescence examination suggest that the initial accumulation of rabbit immunoglobulins in the glomerular mesangium is probably due to direct local binding of anti-FN antibody rather than trapping of immune complexes formed in the circulation. Quantitation of the direct binding using an in vivo perfused kidney system indicate that only a small fraction of the injected antibodies (less than 1 microgram/kidney) could bind. These studies indicate that (1) mesangial immune deposits may be induced by injection of antibodies to a glycoprotein, fibronectin, which is a normal structural component of the mesangium; (2) the initial accumulation of immunoglobulins in the mesangium is probably related to an in situ binding; and (3) mesangial antigens might be involved, in certain cases, in autoimmune reactions.

Mesangial IgA nephritis

Current data suggest that mesangial IgA nephritis is mediated by the mesangial deposition of soluble antigen-IgA class antibody complexes from the circulation. It is likely that common infectious gut flora and dietary antigens contribute to the immune complex load. Defects in antigen exclusion at the mucosa, in the control of IgA production, and in immune complex clearance are postulated to account for each of the recognized clinical syndromes. As yet no effective treatment is available, and a detailed analysis of the mediation pathways will be required before prevention or therapy can be attempted.

Idiopathic mesangial IgA-glomerulonephritis in childhood Description of 19 pediatric cases and review of the literature

Nineteen out of 83 children with asymptomatic haematuria were classified as having IgA glomerulonephritis, characterized by diffuse mesangial deposition of IgA in the absence of systematic disease. Different histological patterns were observed: i.e., minor glomerular lesions (5 cases), focal and segmental proliferative glomerulonephritis (8 cases) and diffuse proliferative glomerulonephritis (6 cases). Recurrent gross haematuria is the clinical hallmark of the disease. Proteinuria was present in 14 children and exceeded 1 g/m2/day in 3 patients. Clinico-pathological correlations showed a close relation between the degree of proteinuria and the histological lesions. Serum IgA levels were elevated in 3 children. Glomerular filtration rate remained above 80 ml/min/1.73 m2 in a 1 to 9 year follow-up.

Complement system in sodium taurocholate pancreatitis in the rat

The role of the complement system was studied in Na-taurocholate pancreatitis in rats. Complement activity (CH 50) was determined at various times in the course of pancreatitis. Immediately after induction of acute pancreatitis, serum complement activity declined and massive C 3 deposits could be detected in the vicinity of acinar necroses and necrobioses. After a phase of recovery three to six hours postoperatively a second complement consumption occurred. Lethality rate increased as serum complement activity fell below 50% of preoperative values. The degree of C 3 deposition increased up to six hours. Decline of serum complement activity and deposition within the pancreas seemed to be correlated with histologically demonstrable tissue lesion. The first decline of complement activity in serum is thought to be caused by liberation of complement activating substances within the pancreas due to the detergent action of Na-taurocholate itself. The second decline, however, may be due to the liberation of complement activating and/or destroying enzymes into the blood stream.

On the pathogenesis of galactosamine hepatitis. Indications of extrahepatocellular mechanisms responsible for liver cell death

In order to evaluate the pathogenesis of galactosamine hepatitis, the action of galactosamine on mast cells, and alteration in the complement system suring the course of this experimental injury were studied. It has been previously demonstrated that rat livers after colectomy are refractory to galactosamine-induced liver cell necrosis and inflammation. For this reason colectomized animals were used to see whether the biochemical alterations produced by this aminosugar and thought to be responsible for cell death developed. Results showed: 1. galactosamine potently degranulates mast cells in vivo and in vitro, 2. the complement system is a) activated during the course of galactosamine hepatitis, probably by circulating endotoxins, and b) is essential for liver cell death in galactosamine hepatitis, and 3. colectomy does not prevent biochemical changes known to occur during galactosamine metabolism. It is concluded that death of galactosamine-injured liver cells is triggered by extrahepatocellular mechanisms, which lead ultimately to an activated complement system by endotoxins. It is postulated that related mechanism may also occur in viral hepatitis and in fulminant hepatic failure in man.

Complement-mediated acinar cell necroses in pancreatitis induced by basement membrane antibodies

To study the role of the serum complement system in the early necrosis of acinar cells an acute pancreatitis was produced by injection of basement membrane antibodies into the pancreatic duct of mice and rats. In all animals deposition of complement (C3) and antibasement membrane IgG could be observed in an identical position within areas of acinar cell necrosis. The extent of parenchymal damage and the intensity of complement deposits corresponded to the injected dose of antibodies. The importance of cytolytically active complement components (C5-9) was demonstrated in congenitally C5-defective old line mice which did not show typical centrolobular necroses 1 hr after intraductal injection of antibodies. However, the normocomplementemic mice developed extensive necroses of acinar cells. The results support the hypothesis of a complement-induced acinar cell necrosis in acute pancreatitis.

[Experimental demonstration of an identic antigenicity of the inner ear and kidney (author's transl)]

An allergic glomerunephritis was produced in rats by injection of an anti-basement-membrane-serum (IgG-fraction), taken from rabbits which were sensitized against a basement membrane fraction of rat-glomerula. Tissues from heart, liver, brain, lung and inner ear were compared with the well known alterations of the glomerula. Exclusively in stria vascularis and renal glomerula heavy changements of the basement membranes and endothelial cells could be shown by electronmicroscopic examination and by immunohistological methods.