Lipopolysaccharide-induced glomerulonephritis develops in the absence of interferon-gamma signaling

IFN gamma is a costimulator of macrophage activation and it plays an important role as a proinflammatory cytokine by upregulation of adhesion molecules and MHC antigens. In this study we tested the role of IFN gamma in a model of endotoxin-induced glomerulonephritis. A systemic lupus-like disease was induced by injection of 50 micrograms bacterial LPS twice a week for 4 weeks in wild-type and in IFN gamma receptor-deficient (IFN gamma R-/-) mice. The renal cortex was examined by immunofluorescence and by light microscopy. LPS treatment induced an increase in serum levels of IgG and anti-dsDNA antibodies. A mild glomerulonephritis was characterized morphologically, but proteinuria was not observed. The main histological features of glomerulonephritis were an increase in ICAM-1 expression, deposition of immune complexes and of complement in the glomeruli, increased mesangial matrix and mesangial hypercellularity. The number of intraglomerular leukocytes, detected by MHC class-II and LFA-1 expression increased roughly 4-fold. All those alterations took place in a similar manner in wild-type and in IFN gamma R-/-mice. Therefore it is concluded that IFN gamma does not play an important role in the development of endotoxic glomerulonephritis.

In vivo treatment of Heymann's Nephritis using a cytotoxic protein-toxin conjugate

In this study we investigated the possibility of treating Heymann's Nephritis (HN) by destroying antibody producing cells by targetting a toxin, gelonin--conjugated to gp330, the renal brush border antigen. HN was induced in rats by immunizing them with purified gp330. The gelonin-gp330 conjugate was administered 12 days after the antigenic challenge. Serum was screened for circulating antibodies. Proteinurea was estimated. The gp330-gelonin conjugate-treated animals had a circulating antibody titre in the serum much lower than that of diseased (untreated) animals. Proteinurea seen in diseased animals was not observed in treated animals. This work suggests the possibility of using a toxin-antigen conjugate for immunomodulating antibody mediated autoimmune renal disease.

Enhancement of renal disease in BXSB lupus prone mice after prior exposure to bacterial lipopolysaccharide

The mechanism, or mechanisms, responsible for enhancement of renal disease after episodes of infection are poorly understood. We used the BXSB mouse as a lupus model of autoimmune disease and we used bacterial lipopolysaccharide (LPS) as a surrogate infectious agent to gain some insight into the mechanism by which infections promote enhancement of autoimmune disease to chronicity. BXSB mice were exposed to LPS for 5 weeks, LPS was withdrawn and various tests and measurements were performed 6 weeks thereafter. Matched BXSB mice exposed to vehicle injections for 5 weeks served as controls. We verified that previous exposure to LPS enhances polyclonal B cell activation, impairs carrier function of blood cells for immune complexes, increases deposition of immune complexes in the microcirculation and promotes glomerular inflammation and sclerosis. These changes occurred at 6 weeks after withdrawal of LPS in the presence of unimpaired function of mononuclear phagocytes. Some of the effects of LPS are reversible, others are partially so and others are irreversible. Altered immune functions elicited by prior exposure to LPS can result in enhanced involvement of various renal compartments and can result in renal insufficiency.

Crescentic glomerulonephritis in interferon-gamma receptor deficient mice

Activation of macrophages by T cells is considered an initiating event in glomerular crescent formation. Since interferon-gamma (INF gamma) is a key mediator in T-cell-mediated activation of macrophages, we decided to test its role in a model of crescentic glomerulonephritis. An anti-glomerular basement membrane (GBM) serum was injected intravenously in presensitized wild-type or IFN gamma receptor deficient (IFN gamma(R)-/-) mice. Glomerulonephritis with glomerular crescents and tubulointerstitial inflammation developed in both strains, even though most evaluated morphological parameters and proteinuria indicated a less severe pathology in the mutant mice compared to the wild type. Thus, IFN gamma is not essential either for glomerular crescent formation or for tubulointerstitial involvement in anti-GBM glomerulonephritis in mice. In conclusion, the role of macrophages in this model might have been overestimated, or other cytokines may compensate for deficient IFN gamma signaling in the activation of macrophages.

Principal cell-specific antigen and hormonal regulatory network in RC.SVtsA58 cell line

We used a dual immunomorphological and physiological approach to demonstrate that the RC.SVtsA58 rabbit cortical cell line exhibits features of highly differentiated cortical collecting tubule (CCT) principal cells (PC). First, we raised monoclonal antibodies against RC.SVtsA58 cells and screened their reactivity with the rabbit kidney: three were specific for the basolateral domain of CCT PC and bound to 100% of RC.SVtsA58 cells. Second, we showed that bradykinin, atrial natriuretic peptide, and prostaglandin E2 increased intracellular Ca2+, guanosine 3',5'-cyclic monophosphate, and adenosine 3',5'-cyclic monophosphate (cAMP), respectively. In addition, 10 nM bradykinin inhibited desmopressin-elicited cAMP production by > or = 40%; this effect was suppressed by 10 microM of indomethacin and was reproduced with 1 nM of prostaglandin E2, indicating the conservation of arginine vasopressin-related regulatory loops described in microdissected CCT and freshly isolated cells. However, RC.SVtsA58 cells also express intercalated cell markers even after repeated cloning, which suggests that tsA58, a temperature-sensitive strain of simian virus-40, has transformed a multipotent type of PC in keeping with the cell interconversion hypothesis.

Endogenous complement C3 synthesis in immune complex nephritis

Human renal epithelial and mesangial cells have been shown to synthesise complement C3 in culture, but the relevance of this finding to the development of complement-mediated nephritis is uncertain. We investigated C3 gene expression in tissue biopsies that showed three main categories of renal injury. By semiquantitative polymerase chain reaction, biopsies from patients with immune-complex glomerulonephritis and those with cell-mediated interstitial nephritis showed increased C3 expression (p < 0.05), but biopsies from patients with non-immune glomerular injury did not. These findings suggest that local C3 production is enhanced in immune-mediated nephritis and are consistent with the hypothesis that locally synthesised complement components are involved in the pathogenesis of tissue injury.

Interferon-gamma regulation of human renal cortical epithelial cell-derived monocyte chemotactic peptide-1

The chemoattractant signal(s) that results in the transmigration of monocytes/macrophage into the tubulointerstitium during acute inflammation is not known. Monocyte chemotactic peptide-1 (MCP-1), a recently described chemotactic cytokine, may function as both a potent monocyte chemotaxin and activator in renal inflammation. We have studied the proinflammatory conditions in which cultured human renal cortical epithelial cells (RCEC) of tubular origin may be stimulated to produce MCP-1. RCEC were stimulated in a dose-time dependent manner with: IL-1 beta (0.01 to 1.0 ng/ml), TNF (0.1 to 10 ng/ml), LPS (0.1 to 10 micrograms/ml) or INF-gamma (10-1000 U/ml). Conditioned media from RCEC stimulated with either IL-1 beta or INF-gamma produced a monocyte chemoattractant activity which was significantly suppressed with neutralizing antibody to MCP-1. Stimulation of RCEC with either IL-1 beta or INF-gamma resulted in a significant (4- to 5-fold) increase in steady state levels of MCP-1 mRNA. MCP-1 antigenic peptide in RCEC conditioned media was significantly increased over control (2- to 2.5-fold) after stimulation with either IL-1 beta or IFN-gamma. In contrast, production of interleukin-8 (IL-8), a neutrophil chemotactic cytokine, was not stimulated by IFN-gamma in RCEC. Thus, the chemokine signaling repertoire of renal tubule cells may be selectively controlled by IFN-gamma.

Identification and epitope analysis of the renal Na+/Pi cotransport protein using monoclonal antibodies

Seven monoclonal antibodies (mAbs) were raised against a rabbit renal brush-border glycoprotein (molecular mass, 63-66 kDa), presumably involved in Na+/Pi cotransport, which we had previously purified and reconstituted in active form in proteoliposomes (Debiec, H., Lorenc, R., and Ronco, P. M. (1992) Biochem. J. 286, 97-102). Antibody specificity for the 63-66-kDa protein was analyzed by enzyme-linked immunosorbent assay and confirmed by Western blotting and immunoaffinity chromatography of solubilized brush-border membranes (BBM), which both yielded a single 63-66-kDa band. Enzyme-linked immunosorbent assay and immunoblotting of renal cortical cell subfractions localized the immunoreactive protein to the brush-border membrane. This location was confirmed by indirect immunofluorescence of kidney cortex sections. Binding of two of the seven mAbs (63A20 and 206A126) to native BBM only occurred when the related epitope was exposed in the presence or absence of Na+, respectively; the other mAbs did not react with native BBM probably because of intramembranous orientation of the epitopes. mAb 63A20 inhibited dose-dependently Na+/Pi cotransport when preincubation of BBM was carried out in the presence of Na+ but did not affect Na+/D-glucose cotransport. Proteoliposomes formed from BBM proteins depleted of the 63-66-kDa protein by affinity chromatography with mAb 63A20 showed an 85% reduction in Na+/Pi cotransport, whereas Na+/D-glucose cotransport was not modified. These results thus establish that the 63-66-kDa BBM protein is the essential component of the Na+/Pi cotransport system. The present study also provides the first immunologic tools available for immunohistochemical localization of the Na+/Pi cotransporter. Finally, the identification of a functional epitope by mAb 63A20 opens up new ways to explore the molecular aspects of Pi uptake.

Expression of a monoclonal antibody (3G5) defined ganglioside antigen in the renal cortex

The monoclonal antibody (mAb) 3G5 was found, by indirect immunofluorescence, to bind to renal cortical structures in frozen sections of human, rat and calf kidneys. Double indirect immunofluorescence studies on frozen sections of rat kidneys showed that 3G5 stained only the glomerulus and the distribution of the 3G5 antigen on the glomerulus was more extensive than the staining observed with antibodies to Factor VIII antigen. 3G5 stained the proximal convoluted tubules and collecting tubules in bovine renal sections but glomeruli did not stain with 3G5. The 3G5 mAb did not stain tissue cultured bovine glomerular endothelial cells or mesangial cells, but did stain bovine glomerular epithelial cell cultures. 3G5 did not stain MDCK cell cultures. The binding of mAb 3G5 to glomeruli was investigated by immunoelectron microscopy of rat renal tissue. In contrast to the podocyte specificity on bovine glomerular cells in vitro, it was found that the specificity of 3G5 expression on rat glomerular cells in vivo was broader. No binding of mAb 3G5 was found outside the glomerulus in the rat renal cortex. Podocytes, endothelial cells and capsular epithelial cells expressed the 3G5 antigen most strongly. A lesser amount of binding was found in the glomerular basement membrane. The mesangium showed a little binding of mAb 3G5 and no binding at all was found to other cortical structures. The 3G5 antigen in rat renal tissue was found to be a glycolipid that migrated between the ganglioside markers GM2 and GM1 by immunostaining of thin layer chromatograms.(ABSTRACT TRUNCATED AT 250 WORDS)

Equine glomerulonephritis and renal failure associated with complexes of group-C streptococcal antigen and IgG antibody

A 12-year-old thoroughbred gelding died from diffuse global glomerulonephritis, 3 months after a lower respiratory infection from which Streptococcus zooepidemicus was isolated. Immunopathological studies (immunofluorescence, immunodiffusion, immunoperoxidase testing and immunoblotting) indicated the presence of an immune reactant renal disease associated with IgG antibody and streptococcal antigens.

In vitro and in vivo interleukin-8 production in human renal cortical epithelia

The signals resulting in leukocytes infiltrating the tubulointerstitial compartment during renal inflammatory disease are not well understood. A recently described cytokine, interleukin-8 (IL-8), has been demonstrated to be chemotactic for lymphocytes and neutrophils at picomolar and nanomolar concentrations, respectively. Cytokeratin positive, renal cortical epithelial cells (RCEC) with tubular attributes were cultured from kidney tissue from six human subjects. We report that these human renal cortical epithelial cells in primary cell culture respond to either IL-1 beta, TNF or LPS in both a time- and dose-dependent manner by expressing IL-8 mRNA and secreting antigenic IL-8 peptide. In addition, RCEC were found to be strongly positive for cell-associated antigenic IL-8 peptide by immunostaining after 24 hour incubation with IL-1 beta, TNF and LPS. To ascertain whether IL-8 was present in renal disease associated with infiltrating leukocytes, we performed immunohistochemistry on renal biopsy specimens from patients with acute allograft rejection. Both proximal and distal tubular epithelial cells were found to be strongly positive for cell-associated antigenic IL-8. These findings suggest that the human renal tubule epithelial cell may actively participate in acute inflammatory processes in the kidney, including allograft rejection, by effecting and directing leukocyte chemotaxis via the production of IL-8.

Immunological recognition of sodium/D-glucose cotransporter from renal brush border membranes by polyclonal antibodies

Antisera prepared in rabbit to a D-glucose-inhibitable phlorizin binding component of the pig kidney brush border membrane precipitated more than 90 percent of the D-glucose-inhibitable phlorizin binding activity from a Triton extract. These antibodies also stimulated D-glucose uptake by native brush border membranes at low D-glucose concentrations (1 mM) and inhibited it at higher D-glucose concentrations. Immunoblotting was used to locate polypeptide subunits of the glucose transporter in polyacrylamide gels of proteins extracted from the brush border membranes. The antibodies labelled the Mr 70,000 phlorizin-binding component in both reducing and non reducing conditions. Two additional polypeptides with relative molecular mass of 120,000 and 45,000 were also recognized under the same conditions; they might correspond, respectively, to another Na+/D-glucose cotransport unit and to a post mortem degradation product.

The complement-inhibiting protein, protectin (CD59 antigen), is present and functionally active on glomerular epithelial cells

Protectin (CD59 antigen) is a 20-kD phosphatidyl-inositol-linked membrane protein that inhibits formation of the membrane attack complex (MAC) of complement on homologous cells. Although the antigen has been identified in a number of human tissues, until recently a functional role had been demonstrated only in circulating cells. Using immunofluorescence techniques we have shown the presence of protectin on human glomerular epithelial cells (GEC) in culture and on GEC, tubular epithelial cells and endothelial cells in frozen sections of normal human renal cortex. In addition, we present evidence that this protein functions in protection of GEC from homologous complement: cultured cells incubated with the Fab2 fragment of a monoclonal anti-protein antibody were markedly more susceptible to killing by homologous serum than were cells in the absence of Fab2 anti-protectin. These findings suggest that this protein may be important in the maintenance of glomerular integrity in vivo, and may be of relevance in certain renal diseases.

Tubulointerstitial nephritis during the heterologous phase of nephrotoxic serum nephritis

This study was designed to characterize the immunopathology of acute tubulointerstitial disease in nephrotoxic serum nephritis in nonsensitized rats. Groups of Lewis rats were studied at 12 time periods ranging from 10 min to 28 days after nephrotoxic serum injection. Nephritic rats developed interstitial nephritis during the acute heterologous phase of renal injury. Coincident with the focal deposition of nephrotoxic antibodies along tubular basement membranes at 24 h, an influx of polymorphonuclear cells and macrophages was evident. The most prominent infiltrate, present between days 3 and 7, was dominated by macrophages with smaller numbers of lymphocytes that were mainly cytotoxic T cells. Dual-labeling studies demonstrated the colocalization of linear tubular basement membrane deposits of the nephrotoxic antibody with focal clusters of interstitial lymphohemopoietic cells. Increased complement deposition was not evident along the tubular basement membranes; moreover, C3 depletion with cobra venom factor failed to attenuate the interstitial inflammation. During the late autologous phase of glomerulonephritis, tubular basement membrane deposits of rat IgG did not appear and the interstitial disease resolved. The results of this study demonstrate that the heterologous phase of nephrotoxic serum nephritis is an antibody-mediated disease directed against the basement membranes not only of the glomeruli but also of some tubules. Antibody deposition is followed by an acute influx of phagocytic cells to both regions of the kidney. These cells may play an important role in the genesis of acute interstitial injury and chronic interstitial fibrosis associated with antiglomerular basement membrane nephritis.

Characterization of a tubular basement membrane component reactive with autoantibodies associated with tubulointerstitial nephritis

A kidney tubular basement membrane (TBM) component that is bound by antibodies from individuals with anti-TBM antibody-associated tubulointerstitial nephritis (TIN) was purified and characterized (TIN antigen). TIN antigen was prepared from rabbit TBM by extraction with guanidine and purified by ion-exchange, gel filtration, and reversed-phase chromatography. Based upon yields of protein and antibody reactivity, TIN antigen accounts for about 9% of the mass of TBM and thus is a major component of this basement membrane. A predominant 58-kDa form comprises about 90% of purified TIN antigen, and a 50-kDa form accounts for the remainder. The two forms share the amino-terminal sequence Ser-Ile-Phe-Gln-Gly-Gln-Tyr-X-Arg-Ser-Phe-Gly- and give similar tryptic peptide maps, indicating that they are structurally related. Their amino acid compositions overall are similar to laminin and entactin/nidogen. The absence of hydroxyproline and hydroxylysine and the low levels of glycine in TIN antigen indicate that it is noncollagenous. No similarities were found between other known proteins and sequences of tryptic peptides and the amino terminus of TIN antigen, suggesting that it is distinct from other characterized basement membrane components. A goat polyclonal antibody toward rabbit TIN antigen showed the same kidney distribution as human antibodies and was completely inhibited in enzyme-linked immunosorbent assay by purified TIN antigen. These data further support the idea that TIN antigen is the primary target for anti-TBM antibodies associated with TIN. This research presents methods to prepare TIN antigen for biochemical studies and investigations of its role in anti-TBM autoimmune TIN.

Intraglomerular leukocyte recruitment during nephrotoxic serum nephritis in rats

Although circulating phagocytic cells are important mediators of glomerular injury, their recruitment mechanisms are not completely understood. In this study, the intraglomerular trafficking of leukocytes was characterized in a rat model of acute glomerular injury induced by nephrotoxic serum (NTS). Polymorphonuclear (PMN) cells infiltrated, then disappeared rapidly, reaching a peak at 2 hr. By 6 hr the PMN migration had almost reversed but small numbers persisted until Day 7. The monocyte influx began almost simultaneously but was of lesser magnitude. However, the number of ED-1+ monocytes increased progressively from 60 min to reach a plateau by Day 2 and persisted to the end of the study (Day 28). Quantitation of intraglomerular Ia+ cells suggested in situ activation of monocytes within the glomeruli. Increased Ia+ cells were first evident on Day 2. By Day 5, 80% of the intraglomerular macrophages were Ia+. Complement depletion with cobra venom factor abrogated early albuminuria, delayed the initial PMN influx, but failed to attenuate monocyte migration. T lymphocytes appeared briefly between 10 min and 2 hr. In vitro proliferation study failed to demonstrate lymphocyte sensitization to glomerular basement membrane (GBM) antigens. A unique population of cells (OX19 OX8+), possibly representing natural killer cells, was present from Day 1 to Day 14. During the secondary wave of proteinuria (autologous phase), all leukocytes had disappeared except for macrophages and a small number of OX19-, OX8+ cells. A complex intraglomerular migration of leukocytes was triggered by the binding of nephrotoxic antibodies to GBM antigens. We speculate that this cascade involves several cell-to-cell interactions necessary for the full expression of glomerular injury.

Definition of glomerular antigens by monoclonal antibodies produced against a human glomerular membrane fraction

Experimental animal models of glomerulonephritis (GN) produced by direct antibody binding to non-basement membrane glomerular capillary wall antigens do not to date have human parallels. To examine the potential for this form of humoral glomerular injury in man, we sought to define discrete human non-GBM glomerular antigenic targets using hybridoma technology. Mice were immunised intraperitoneally with 20-100 micrograms of a human glomerular membrane fraction (HGMF). Six fusions have yielded 12 stable reagents defined by positive glomerular indirect immunofluorescence (IF) and microELISA using HGMF as the screening antigen. Subclass analysis of ascitic McAbs indicated several IgG1, one IgG2b, and three IgM reagents. Distinctive IF patterns of reactivity with epithelial, endothelial or mesangial structures have been observed, with or without peritubular capillary, tubular basement membrane and vessel wall reactivity. Seven normal non-renal human organs and the kidneys of rat, rabbit and sheep have shown patterns characteristic of each individual McAb, restricted to human or with species cross reactivity. To partially characterise McAb-reactive antigens, detergent-solubilised renal cortex and collagenase-solubilised GBM (CS-GBM) extracts have been probed by immunoblot. A unique McAb 7-5Q, reactive with glomerular and tubular epithelial structures, binds major bands of approximately 107 KD and 93 KD in detergent solubilised cortex and a single band of similar size by immunoprecipitation (110 KD). 5-3A (a human-restricted linear-reacting McAb) binds bands of 20-200 KD (major band 58 KD) in CS-GBM. In conclusion, distinct species-restricted and more broadly disposed glomerular epitopes are definable in man by McAbs and are potential targets for humoral injury. Purification of these antigens will allow assay for circulating putative nephritogenic auto-antibody and potentially, McAbs may be useful in screening urine for evidence of occult structural renal disease.

Postnatal development of the interstitial tissue of the rat kidney

To study the ontogenetic development of the interstitial tissue of the kidney, rats were investigated 1, 3, 7, 14, 21 and 28 days after birth. Kidneys perfusion-fixed with glutaraldehyde were studied with light- and electron microscopy. Cryostate sections from kidneys immediately frozen in liquid nitrogen were studied with respect to the expression of MHC class II antigen using the monoclonal antibody OX6. The interstitial space of both the renal cortex and the outer and inner medulla was prominent during the first days postnatally. The relative interstitial volume of the cortex and outer part of the medulla then decreased in conjunction with the outgrowth and maturation of the superficial nephrons while the inner medullary interstitium remained wide. During the first postnatal days, the abundant interstitial cells of the cortex were connected via cytoplasmic processes to form a loose network which later became less well defined. The lipid-laden interstitial cells of the inner medulla showed essentially the same ultrastructure in the newborn as in the adult animal. Strong expression of class II antigen first appeared on epithelial cells of the thick ascending limb of Henle's loop about 7 days postnatally, and became weak at 28 days. From 21 days, a weak staining of the proximal tubules was also observed. While interstitial cells in the inner medulla were always negative, cortical and outer medullary interstitial cells became strongly positive for class II antigen from day 21 post partum.

Chronic serum sickness glomerulonephritis: heparin enhances the removal of glomerular antigen

Chronic serum sickness glomerulonephritis was induced in rats using 125I-labelled cationic bovine serum albumin as antigen. During the recovery period the animals were given protamine or polyethyleneimine (PEI), both of which are cationic, or heparin, which is anionic. A control group received saline. The cationic molecules were not shown to influence the rate of removal of antigen from the glomeruli, but heparin increased removal. In subsequent experiments this effect of heparin was confirmed, and a similar effect was demonstrated using low molecular weight heparin. These results indicate that large doses of heparin can enhance the removal of antigen from well-established glomerular deposits. Fibrin is not detectable in the glomeruli in this model, so this effect of heparin may be independent of its anticoagulant properties.

The effect of cyclosporin A on the interstitial mononuclear cell infiltration and the induction of Heymann's nephritis

Heymann's nephritis was induced with brush-border (BB) antigen. Interstitial mononuclear cell infiltration was studied with cytological examinations of fine-needle aspiration biopsies (FNAB), and with immunoperoxidase stains of frozen sections with monoclonal antisera. The effect of cyclosporin A (CyA), 20 mg/kg when administered intraperitoneally for 8 days in association with both initial immunization, and with the booster 4 weeks later, on the interstitial leukocyte infiltration and on the development of membranous glomerulonephritis (MGN) and proteinuria were investigated. Another group of rats was immunized, but not given CyA. Experimental animals were killed in groups 3, 6 and 20 weeks after initial immunization. CyA inhibited significantly the initial interstitial lymphocyte and blast cell response at 3 weeks (FNAB), but did not inhibit the secondary response after the booster. The anti-BB titre reacted in a similar fashion. Immunoperoxidase stains indicated a clearly suppressed T suppressor/cytolytic (T s/c) cell response. Glomerular basement membrane (GBM) deposits of IgG developed more slowly and were more scarce in the CyA-treated rats, when compared with the untreated group. Only one out of 15 CyA treated rats developed C3 deposits in the GBM during the course of the study, and none developed proteinuria, when most untreated rats (10/17) had C3 deposits and were nephrotic at 20 weeks. Thus, CyA depressed the initial interstitial cellular response after immunization with BB antigen, and also inhibited the development of antibody response, C3 deposits and proteinuria of Heymann nephritis. These effects of CyA may be contributed to an inhibited amplification of the autoimmune response associated with interstitial damage and continuous release of autoantigen.

Characterization of a polyreactive monoclonal antibody to dsDNA, F x 1A, and heparan sulfate generated from BALB/c mice immunized with rat renal homogenates

Monoclonal antibodies (MoAb) were prepared by fusing spleen cells from BALB/c mice immunized with rat renal cortical homogenates to the mouse myeloma cell. One of them, designated MoAb26-3, revealed a positive antinuclear activity by screening an indirect immunofluorescence test on kidney cryostat sections. The reactivity of MoAb26-3 with double-stranded deoxyribonucleic acid (dsDNA) was confirmed by the Crithidia luciliae assay. The isotype of MoAb26-3 was determined to be IgM-kappa. To test the nephritogenicity of MoAb26-3, the hybridomas were grafted intraperitoneally into BALB/c mice. A deposition of IgM was observed along the base of the epithelial foot processes and on the luminal surface of the endothelium by immunoelectron microscopy. By direct enzyme-linked immunosorbent assay (ELISA), MoAb26-3 was shown to react not only with dsDNA but also with fraction 1A of renal cortical supernatant (F x 1A) and heparan sulfate. On the basis of inhibition ELISA, the dsDNA inhibited F x 1A and heparan sulfate binding of MoAb26-3 and F x 1A blocked the reactivity of Mo26-3 with dsDNA and heparan sulfate, while heparan sulfate showed a less inhibition on the binding of MoAb26-3 with F x 1A, dsDNA, and even with heparan sulfate. Using immunoprecipitation with radiolabeled F x 1A, MoAb26-3 was shown to react with MW 330,000, 440,000, and 700,000 bands which were the same with those which polyclonal Heymann nephritis serum could react. An intravenous injection of MoAb26-3 to rats resulted in the deposition of IgM along the glomerular capillary wall, but resulted in an only transient appearance of proteinuria.

Sequential localization of antibody to multiple regions of the glomerular capillary wall in passive Heymann nephritis

Passive Heymann nephritis was produced in rats by injection of the multispecific anti-Fx1A antibody. At time points 1 hour, 1 day, 2 days, 3 days, and 4 days groups of rats were sacrificed and their kidneys fixed by retrograde perfusion with paraformaldehyde lysine periodate. The antibody was visualized by direct immunofluorescence and by 125I-Protein-A electron microscopic autoradiography. Localization of the antibody in the lamina rara interna, lamina densa, lamina rara externa and the glomerular epithelial cell was determined by electron microscopic autoradiography according to the method of Saltpeter, Fertuck, and Saltpeter (Saltpeter MM, Fertuck MC, Saltpeter EE: J Cell Biol 72:161, 1977). At least 100 grains/kidney were analyzed. At one hour the antibody was localized in a linear, discontinuous pattern by immunofluorescent microscopy. Ultrastructurally, the antibody was present in all regions of the capillary wall although predominantly in the lamina rara interna. At later time points the immunofluorescence staining changed to the typical granular pattern with majority of the grains localizing to the lamina rara externa and the cell body of the glomerular epithelial cell. The importance of these observations is several-fold. (a) It suggests the involvement of multiple antigens in the pathogenesis of Heymann nephritis. (b) The initial reaction to the lamina rara interna may be potentiating the eventual formation of deposits in the lamina rara externa by locally permeabilizing the capillary wall and allowing passage to other antibodies. (c) The immune complexes formed at the various sites in the capillary may be getting shed and trapped in the lamina rara externa resulting in coalescence and genesis of the nephritogenic electron-dense deposits.