Involvement of an antigen distinct from the Heymann antigen in membranous glomerulonephritis in the mouse.

Membranous glomerulonephritis in the mouse can be induced by injection of a heterologous antiserum against murine pronase digested renal tubular antigens (TApron). The antigenic target in the glomerular capillary wall is different from the Heymann antigen (gp 330). It shows the characteristics of a smaller antigen (gp 90) that can also be detected by a monoclonal antibody. We isolated the anti-gp 90 component from the polyclonal antiserum by absorptions and elutions using mouse liver as a substrate, which lacks gp 330 but does express gp 90. Immunoprecipitation of radiolabeled renal proximal tubular brush borders demonstrated that the mouse liver eluate reacted with gp 90 but not with gp 330. In immunofluorescence, the eluate bound to the glomerular capillary wall of both mouse and rat in a homogeneous pattern. Injection of the eluate led to a transient, homogeneous binding to the glomerular capillary wall of the mouse and also, although to a lesser extent, to that of the rat. Injection in mice presensitized against rabbit immunoglobulins caused a more permanent granular binding in a pattern typical of membranous glomerulonephritis. The results demonstrate that an antigen with a molecular weight and a kidney distribution different from the Heymann antigen can serve as target for antibody-mediated membraneous glomerulonephritis in the mouse. Furthermore, they suggest that this antigen may also be involved in the membranous glomerulonephritis of the rat in addition to the Heymann antigen.

The organ distribution of gp-330 (Heymann antigen) and gp-90 in the mouse and the rat.

The Heymann antigen (gp-330) and an antigen with lower molecular weight (gp-90) are major constituents of the brush border of the renal proximal tubules in the rat and the mouse. The Heymann antigen can also be found at discrete sites in the glomerular visceral epithelium of the rat, but not of the mouse. Gp-90 is present diffusely along the glomerular capillary wall of rat and mouse. The Heymann antigen is probably the target antigen for membranous glomerulonephritis in the rat, while in the mouse, where this form of glomerulonephritis can also be induced, gp-90 seems to be the antigen involved. We have separated the antibody populations against these two antigens by preparing eluates from kidneys of rats and livers of mice that had been injected with an antiserum against pronase-digested mouse renal tubular antigens. Using these purified antibodies we have examined by indirect immunofluorescence the distribution of the two antigens on normal mouse and rat tissues. The expression of the Heymann antigen is limited to the epithelia of several organs, while gp-90 has a more widespread distribution in many cells of different origin and function in both the mouse and the rat.

Comparison of antigenic targets involved in antibody-mediated membranous glomerulonephritis in the mouse and rat.

Membranous glomerulonephritis in the mouse can be induced by a single injection of an antiserum against homologous, pronase-digested, renal tubular antigens (TAPron). In indirect immunofluorescence studies on normal mouse and rat kidneys it has now been found that the antiserum reacts strongly with the visceral epithelia of the mouse in a homogeneous pattern, while a faint granular staining is seen in the rat glomerulus against a homogeneous background. After injection in rats, a classic passive Heymann nephritis could be induced. By immunoprecipitation of radiolabeled rat renal brush borders (BB) it could be shown that anti-TAPron antisera contain antibodies to 330-kd and 90-kd BB proteins expressed by rat glomeruli. With the use of two monoclonal antibodies specific for the 330- and 90-kd proteins the homogeneous binding observed in rat and mouse glomeruli could be related to the 90-kd antigen, whereas the coarse irregular staining observed in rat glomeruli was only related to the 330-kd antigen. Immunoglobulins eluted from glomeruli of rats bound to rat glomeruli and reacted only with the 330-kd protein. They did not bind to mouse glomeruli. Discrete localization in coated pits, multivesicular bodies, and endoplasmic reticulum of the visceral epithelia was seen in immunoelectron-microscopy. The results presented thus demonstrate that immune deposits induced in the rat by anti-TAPron antibodies are related to antibodies specific for the 330-kd antigen, ie, the classic Heymann antigen. By contrast, immune deposits observed in the mouse are related to antibodies specific for a 90-kd protein.

Anti-GBM nephritis in the mouse: severe proteinuria in the heterologous phase.

Highly reproducible anti glomerular basement membrane (GBM) nephritis has been induced in the mouse after a single injection of rabbit or goat antibody against purified homologous GBM. The severity of albuminuria was closely related to the amount of antibody given. With doses of 4 mg or more, low serum albumin concentrations, sometimes accompanied by ascites and oedema, were observed after 1 week. Glomerular injury was characterized by an initial accumulation of polymorphonuclear granulocytes followed by thrombosis and necrosis, the extent of which defined the outcome of the glomerulonephritis. With high doses of antibody the exudative lesions entered a chronic phase, while at doses lower than 2 mg remission of the lesions occurred. Immunofluorescence studies showed prompt linear fixation of the injected antibodies to the glomerular capillary wall, accompanied by immediate binding of C3 in a fine granular pattern. Fibrin deposits appeared at 2 h in some glomeruli, increased thereafter, and were present after one day in more than 90% of the glomeruli in mice that had received 4 mg of antibody. This new reproducible model in the mouse is suited for the study of the relationship between activation of mediator systems, histological lesions, and proteinuria.

Membranous glomerulonephritis in the mouse.

Glomerulonephritis was induced in C57. B110 mice by a single injection of rabbit IgG against homologous, pronase-digested, renal tubular antigens. The heterologous phase was characterized by a transient increase of glomerular permeability with fixation of rabbit IgG to the capillary walls, in a linear or fine-granular pattern, and to the brush borders of the proximal tubuli. The autologous phase was marked by the immune response to the injected protein, during which subepithelial immune deposits, consisting of mouse IgG1, rabbit IgG, and mouse C3 developed. Small amounts were still present at 1 year after the injection of antiserum. The antibody response of the mice correlated with the development and resolution of the deposits. None of the mice developed a nephrotic syndrome. Control mice treated with normal rabbit IgG did not show immune deposits in their kidneys at any stage despite a comparable antibody response to rabbit IgG. Immunoelectronmicroscopy showed that the rabbit antibodies fixed directly to an antigen in the cell membrane of the glomerular visceral epithelium. It seems, therefore, likely that in situ formation of subepithelial immune complexes occurred in the autologous phase by fixation of mouse immunoglobulins to rabbit IgG already present in the glomerular wall.