Anti-Fx1A produces complement-dependent cytotoxicity of glomerular epithelial cells

Glomerular injury in passive Heymann nephritis (PHN) in rats is mediated by the C5b-9 membrane attack complex (MAC) and is associated with morphologic changes in glomerular visceral epithelial cells (GEC). We determined if the nephritogenic antibody of PHN (gamma 1 sheep anti-Fx1A IgG) directs insertion of the MAC into GEC plasma membranes with consequent cytotoxicity. Antibody-sensitized GEC were exposed to various sera serving as sources of complement. Loss of cell viability was determined by trypan blue uptake and/or by release of cellular lactate dehydrogenase (LDH). Incubation of antibody-sensitized primary and passaged GEC in fresh human serum (FHS) resulted in sigmoidal relationships between cytotoxicity and complement dose (r = 0.97 and 0.94, respectively) such that cytolysis approached 100% with FHS (10% vol/vol). Cytotoxicity was not evident if C8-deficient (C8D) plasma was substituted for FHS, but was restored in a dose-dependent manner by reconstitution with purified rat C8. Sublytic injury was demonstrated by wide separation between simultaneous release curves of cell-incorporated biscarboxyethyl carboxyfluorescein (BCECF; mol wt approximately equal to 520) and LDH at limiting doses of complement (at 2% FHS, BCECF release was 51.1 +/- 0.6% of maximum vs. 3.2 +/- 1.3% for LDH; N = 3) and by blebbing of the plasma membrane on electron microscopy. Thus, the pathogenic antibody of PHN produces complement-mediated sublytic as well as lytic cytotoxicity of GEC.

Effect of diet, age and sex on the renal response to immune injury in the rat

We investigated the effect of three factors, namely dietary protein intake, age and sex, on the susceptibility of the renal glomerulus to the binding of antiglomerular basement membrane antibody (anti-GBM) in the early (heterologous) phase of anti-GBM nephritis, and the consequent reduction in glomerular filtration rate (GFR) as measured by inulin clearance (CIn). The effect of diet was examined in approximately equal to 8 week-old female Munich-Wistar rats fed a 40% high (HP) or a 6% low (LP) protein diet, and that of sex and age in male and female rats, 6 week or 10 month old. Following an intravenous dose (3 to 20 micrograms/g body wt) of radiolabeled nephritogenic anti-GBM, assessment of glomerular function was followed by quantitation of anti-GBM binding (values corrected for GBM surface area) in isolated glomeruli. At a given plasma level of antibody, the degree of binding of anti-GBM was slightly but significantly higher in HP than LP-fed rats; the decrease in GFR was significantly more pronounced in HP than LP-fed animals. The amount of anti-GBM binding was significantly greater in adult than young animals; however, the consequent decrease in GFR was more pronounced in the young than adult animals. Sex dependency was not discernible in anti-GBM binding or reduction in GFR. In all of the above experimental groups, the degree of anti-GBM binding was closely correlated with the plasma level of anti-GBM, but not with effective renal plasma flow rate, measured by PAH clearance. Separate groups of rats were subjected to experimental manipulation of single nephron GFR, glomerular capillary hydraulic pressure and glomerular plasma flow rate, by partial aortic constriction and saralasin administration. This set of experiments, using a tracer amount of non-nephritogenic anti-GBM, revealed that glomerular anti-GBM binding is independent of any of the above parameters. The studies indicate that dietary protein intake and age, but not sex, are among the factors determining the susceptibility of the glomerulus to acute immune injury. Since the binding of anti-GBM is determined by the affinity property of the glomerulus per se, and not by the prevailing hemodynamic pattern, the observed dependence of susceptibility to functional impairment on age and protein intake appears to also reflect a property of the glomerulus, which is influenced by age and the degree of dietary protein intake.

Anti-Fx1A induces association of Heymann nephritis antigens with microfilaments of cultured glomerular visceral epithelial cells

Binding of anti-Fx1A to Heymann nephritis antigens (HA) on rat glomerular epithelial cells (GECs) in culture leads to capping and disappearance of antigens from the cell surface. This process may contribute to the formation of glomerular subepithelial immune deposits in vivo. The authors differentially extracted GECs to determine whether HA redistribution is mediated by cytoskeletal components. Observations were made by phase-contrast and immunofluorescence microscopy on primary and passaged GECs in monolayer culture and by spectrofluorimetry on GECs in suspension. GEC-bound sheep anti-Fx1A IgG was detected by fluoresceinated anti-sheep IgG. Microfilaments were identified by rhodamine-phalloidin staining of F-actin. After cross-linking HA on GECs by anti-Fx1A IgG at 0 C, GECs remained polygonal in shape and had diffuse granular IgG staining of their plasma membranes. Treatment of GECs at 0 C with hypotonic buffer containing 0.5% Triton X-100 produced microfilament-rich cytoskeletons that retained the shape of unextracted GECs. Further incubation with DNase I at 37 C removed microfilaments (mean fluorescence declined by 90%) and resulted in the rounding of cytoskeletons. After Triton X-100 treatment, 85% of initial GEC-bound anti-Fx1A IgG remained, but only 29% remained after DNase I. In contrast to intact IgG, detergent-extraction resulted in the complete loss of GEC-bound anti-Fx1A Fab'. Anti-Fx1A IgG did not bind to GECs pretreated with Triton X-100. Thus, cross-linking of HA by anti-Fx1A converts HA from a detergent-soluble, membrane-associated form to an insoluble, cytoskeleton-bound form. Attachment of cross-linked HA to the cytoskeleton is mediated by microfilaments.

Role of abnormally high transmural pressure in the permselectivity defect of glomerular capillary wall: a study in early passive Heymann nephritis

To explore the mechanism of glomerular permselectivity defect in passive Heymann nephritis, an experimental model of human membranous glomerulopathy, Munich-Wistar rats were subjected to both micropuncture assessment of glomerular hemodynamics and whole kidney clearance measurements of graded size dextrans 10 days after injection of sheep anti-rat tubular antigen (anti-Fx1A). Compared with normal control rats, anti-Fx1A-treated animals were characterized by marked proteinuria (65 +/- 8 micrograms/min versus 6 +/- 1, p less than 0.001), markedly and significantly higher glomerular transcapillary hydraulic pressure difference (40 +/- 1 mm Hg versus 33 +/- 1, p less than 0.001), depressed ultrafiltration coefficient and impaired glomerular size-selective function as determined by fractional clearance of dextrans. Calculation of membrane parameters based on a recently defined heteroporous membrane model revealed abnormally high availability of non-size selective, large pore pathways in the glomerular capillary wall of the rats with passive Heymann nephritis. To ascertain the role of the altered hemodynamic pattern in the observed defect in the size-selective function of the glomerular capillary wall, glomerular transcapillary hydraulic pressure difference was manipulated experimentally in these proteinuric rats by intra-aortic infusion of acetylcholine or angiotensin II. These agents respectively suppressed and augmented glomerular transcapillary hydraulic pressure difference and brought about a decline of and a further rise in fractional clearance of larger dextrans along with parallel changes in both urine protein excretion rate and availability of nonselective channels. These results indicate that the permselectivity defect in passive Heymann nephritis is attributable, at least in part, to impaired size selectivity of the glomerular capillary wall caused by a prevailing abnormally high transcapillary hydraulic pressure difference.

A role for thromboxane in complement-mediated glomerular injury

The membrane attack complex (MAC) of complement (C) has been shown to stimulate prostaglandin (PG) and thromboxane (Tx) synthesis in nucleated cells. Because glomerular epithelial cell injury and altered permeability in rat membranous nephropathy are mediated by the MAC, the authors examined whether MAC-induced proteinuria is linked to glomerular prostanoid synthesis. In kidneys containing non-nephritogenic, non-C-fixing gamma 2 sheep anti-Fx1A (planted antigen) that were perfused in vitro with C-fixing guinea pig anti-sheep IgG and a C source (fresh human plasma, 50% vol/vol in buffered bovine albumin), heavy proteinuria developed, reaching 4.27 +/- 1.20 mg/min/g at 100-120 minutes (n = 8). Cyclooxygenase blockade with 10(-4) M indomethacin (n = 6) inhibited urinary PGE2 excretion (569 +/- 47 to 124 +/- 18 pg/min/g, P less than 0.001) and lowered proteinuria (1.06 +/- 0.42 mg/min/g, P less than 0.001). Reduced protein excretion (0.88 +/- 0.12 mg/min/g, n = 6, P less than 0.001) also occurred with inhibition of Tx synthetase by OKY-046, 10(-4) M, a dose that was shown in separate perfusions to inhibit urinary TxB2 excretion by greater than 85%. Control kidneys, without planted antigen and perfused with anti-sheep IgG and plasma, excreted 0.30 +/- 0.05 mg protein/min/g (n = 6). Because inulin clearance was reduced by indomethacin, renal hemodynamic factors may have contributed to the reduction in proteinuria observed with this drug. However, insulin clearance was not significantly affected by OKY-046, implying that inhibition of Tx synthetase reduced proteinuria independently of changes in renal hemodynamics. Thus, proteinuria in rat membranous nephropathy is due to MAC-dependent glomerular epithelial injury and is mediated, in part, by Tx.

The membrane attack complex in complement-mediated glomerular epithelial cell injury: formation and stability of C5b-9 and C5b-7 in rat membranous nephropathy

Using a model of rat membranous nephropathy (MN), we examined the relationship between the development of glomerular epithelial cell injury and the formation and stability of the membrane attack complex (MAC) of complement. Isolated rat kidneys were perfused with buffered bovine albumin (BSA) or various plasmas (complement source). Kidneys containing nephritogenic amounts of complement-fixing sheep antibody to glomerular epithelial antigens (aFx1A) perfused with BSA (n = 5), and normal kidneys perfused with normal human plasma in BSA (50% v/v, n = 6) excreted 0.30 +/- 0.02 mg protein/min/g during 90 min perfusion (control groups). When normal plasma was added to the perfusate of aFx1A kidneys at concentrations of 12.5, 25, and 50% v/v, protein excretion rose in a time- and concentration-dependent manner. Perfusions with 25% plasma resulted in baseline proteinuria from 0 to 20 min that increased to 2.8 +/- 0.9 mg/min/g at 20 to 40 min and 8.6 +/- 2.1 at 40 to 60 min (n = 4, p less than 0.01 vs control groups). Removal of plasma at 20 min did not prevent this rise in protein excretion (3.9 +/- 2.4 and 5.8 +/- 2.6 mg/min/g at 30 to 40 and 55 to 65 min respectively, p less than 0.01, n = 4). Perfusion of aFx1A kidneys with C8-deficient (C8D) human plasma (25% v/v, n = 4) or C6D rabbit serum (25% v/v, n = 2) independently produced low levels of proteinuria comparable with BSA, but in combination, the two reagents restored enhanced protein excretion (n = 2). In aFx1A kidneys containing C5b-7, addition of C8 and C9 (C6D serum) after intervals of 20, 60, or 90 min immediately reconstituted heavy proteinuria. Thus, the magnitude of MAC-induced glomerular epithelial injury in rat MN is related to the complement dose. Altered glomerular permeability is delayed with respect to the onset of complement activation. Once sufficient C5b-9 is formed, proteinuria can develop despite cessation of new MAC assembly, implying that C5b-9 persists after formation. Moreover, the C5b-7 MAC intermediate is not eliminated rapidly in this model.

The membrane attack complex in complement-mediated glomerular epithelial cell injury: formation and stability of C5b-9 and C5b-7 in rat membranous nephropathy

Using a model of rat membranous nephropathy (MN), we examined the relationship between the development of glomerular epithelial cell injury and the formation and stability of the membrane attack complex (MAC) of complement. Isolated rat kidneys were perfused with buffered bovine albumin (BSA) or various plasmas (complement source). Kidneys containing nephritogenic amounts of complement-fixing sheep antibody to glomerular epithelial antigens (aFx1A) perfused with BSA (n = 5), and normal kidneys perfused with normal human plasma in BSA (50% v/v, n = 6) excreted 0.30 +/- 0.02 mg protein/min/g during 90 min perfusion (control groups). When normal plasma was added to the perfusate of aFx1A kidneys at concentrations of 12.5, 25, and 50% v/v, protein excretion rose in a time- and concentration-dependent manner. Perfusions with 25% plasma resulted in baseline proteinuria from 0 to 20 min that increased to 2.8 +/- 0.9 mg/min/g at 20 to 40 min and 8.6 +/- 2.1 at 40 to 60 min (n = 4, p less than 0.01 vs control groups). Removal of plasma at 20 min did not prevent this rise in protein excretion (3.9 +/- 2.4 and 5.8 +/- 2.6 mg/min/g at 30 to 40 and 55 to 65 min respectively, p less than 0.01, n = 4). Perfusion of aFx1A kidneys with C8-deficient (C8D) human plasma (25% v/v, n = 4) or C6D rabbit serum (25% v/v, n = 2) independently produced low levels of proteinuria comparable with BSA, but in combination, the two reagents restored enhanced protein excretion (n = 2). In aFx1A kidneys containing C5b-7, addition of C8 and C9 (C6D serum) after intervals of 20, 60, or 90 min immediately reconstituted heavy proteinuria. Thus, the magnitude of MAC-induced glomerular epithelial injury in rat MN is related to the complement dose. Altered glomerular permeability is delayed with respect to the onset of complement activation. Once sufficient C5b-9 is formed, proteinuria can develop despite cessation of new MAC assembly, implying that C5b-9 persists after formation. Moreover, the C5b-7 MAC intermediate is not eliminated rapidly in this model.

Nephritogenic potential of sheep antibodies against glomerular basement membrane laminin in the rat

Antilaminin antibodies have been shown to bind to laminin within the glomerular basement membrane (GBM) and mesangium of experimental animals but have induced little or no glomerular injury. We used a sheep antiserum to murine Englebreth-Holm-Swarm sarcoma laminin (sheep antilaminin) to further study the potential of antilaminin antibodies to cause glomerular injury. Intravenous injections of sheep antilaminin into rats produced intense linear GBM deposits of sheep IgG but consistently failed to induce heterologous phase proteinuria as previously shown. In addition, no autologous phase injury appeared even after preimmunization with sheep IgG (N = 4) or passive administration of rat anti-sheep IgG (N = 3) (mean urine protein less than 4 mg/24 hours up to 16 days). GBM deposits of rat C3 in vivo were absent despite the ability of both sheep antilaminin and rat anti-sheep IgG to fix human and rat C3 in vitro as determined by an indirect immunofluorescent assay. In contrast, when kidneys containing sheep antilaminin were transplanted into naive recipients that were passively immunized with rat anti-sheep IgG, severe proteinuria occurred (range 7 to 109 mg/24 hours on day 2; 49 to 350 mg/24 hours on day 5 posttransplantation) in association with glomerular deposition of C3. Histological evaluation at day 5 showed a severe proliferative glomerulonephritis with infiltrating polymorphonuclear and mononuclear leukocytes. Electron microscopy showed endothelial and epithelial cell detachment from the GBM and inflammatory cell adherence to denuded GBM. Epithelial foot process effacement and cytoplasmic absorption droplets were also noted. Identical kidneys transplanted into nonimmunized recipients or immunized recipients depleted of complement had significantly less (p less than 0.05) proteinuria (nonimmunized: 5 to 18 mg/24 hours on day 2, 4 to 9 mg/24 hours on day 5; complement-depleted: 6 to 13 mg/24 hours on day 2, 4 to 27 mg/24 hours on day 5) and no glomerular complement fixation was seen in these animals. Thus, severe glomerular injury can be induced by a focused, amplified, complement-dependent immune attack on glomerular laminin. In contrast, the widespread distribution of laminin and antilaminin probably dilutes the total glomerular immune reaction and precludes effective complement fixation and glomerular injury during the autologous phase in nontransplanted kidneys. A similar explanation might account for the lack of glomerular injury in previous studies that utilized antisera to known GBM constituents.

Complement-induced glomerular epithelial cell injury. Role of the membrane attack complex in rat membranous nephropathy

In passive Heymann nephritis (PHN) in rats, antibody (anti-Fx1A) reacts in situ with a glomerular epithelial antigen and induces complement (C)-mediated cell-independent proteinuria. To assess the role of the membrane attack complex (MAC), we determined the need for C8 in the pathogenesis of proteinuria in an autologous-phase model of PHN. Isolated rat kidneys, containing nonnephritogenic, non-C-fixing gamma 2 sheep anti-Fx1A (planted antigen), when perfused in vitro with C-fixing guinea pig anti-sheep IgG and a source of C (fresh human plasma 50% vol/vol in buffer containing bovine serum albumin), developed marked proteinuria after 20 min (0.58 +/- 0.08 mg/min X g, n = 8) that increased further to 3.20 +/- 0.93 mg/min X g after 80 min. In contrast, identical kidneys perfused with antibody and heat-inactivated or C8-deficient human plasma and normal kidneys perfused with antibody and fresh plasma excreted only 0.27 +/- 0.03 (n = 6), 0.27 +/- 0.04 (n = 5), and 0.40 +/- 0.05 mg/min X g (n = 6) after 20 min, and 0.13 +/- 0.02, 0.22 +/- 0.03, and 0.32 +/- 0.05 mg/min X g after 80 min, respectively. When C8-deficient plasma was reconstituted with sources of C8 (n = 3), proteinuria was restored to the level observed with fresh normal plasma. Differences in protein excretion could not be explained by quantitative differences in glomerular antigen or antibody content. Extensive ultrastructural damage to glomerular visceral epithelial cells was exclusively seen in antigen-containing kidneys perfused with antibody and C8-replete plasma. Thus, glomerular injury in this model results from an antigen-specific, antibody-directed, C8-dependent reaction involving assembly of the MAC. The ultrastructural findings argue in favor of MAC-induced cytotoxicity of the glomerular visceral epithelial cells.

Charge selective properties of the glomerular capillary wall influence antibody binding in rat membranous nephropathy

IgG antibodies, eluted from kidneys of rats with Heymann nephritis were separated into cationic and anionic fractions, labeled with 125I and 131I, respectively, mixed in equal amounts, and then injected in incremental doses into 10 rats. Glomerular antibody binding was highly correlated with blood concentration of antibody at 24 hr, however, significantly more cationic antibody bound to glomeruli than did anionic antibody at all blood levels studied. The differences were not due to greater antibody content and/or avidity of the cationic preparation, as measured by binding to isolated glomeruli in vitro. These studies demonstrate the influence of glomerular permselectivity and antibody charge on subepithelial antibody deposition.

Antibody, antigen, and glomerular capillary wall charge interactions: influence of antigen location on in situ immune complex formation

These studies examined the charge interactions between the glomerular capillary wall, antibody and antigen at different sites in the glomerulus. Sheep IgG was separated into differently charged subclasses and immunologically placed in one of two glomerular locations (subepithelial or subendothelial) to serve as planted antigen. Single kidneys with planted antigen were transplanted into uninephrectomized recipients that received affinity-purified, cationic and anionic rat anti-sheep IgG labelled with 125I and 131I, respectively. Glomerular bound antibody was determined and corrected for antibody delivery. Specificity of antibody binding was confirmed by comparison of kidneys with or without planted antigen. The results indicate that the influence of charge on glomerular antibody binding depends on the site of the antigen. When antigen was planted in the subepithelial space, significantly more (15 to 25%) cationic than anionic antibody bound despite the fact that the antigen was cationic. Conversely, when the antigen was planted subendothelially, significantly more anionic (13 to 22%) antibody bound when the antigen was cationic, and significantly more cationic (7 to 16%) antibody bound when the antigen was anionic. Thus, the negatively-charged glomerular filtration barrier retards the permeation of anionic antibodies that complex with antigens located in the subepithelial space, but antigen-antibody charge interactions appear to predominate when the antigen is more proximally located.

Anti-GBM antibody-induced proteinuria in isolated perfused rat kidney

The effect of anti-GBM antibody on protein excretion was studied in isolated rat kidneys perfused with 20 mg of sheep anti-rat GBM (experimental) or nonantibody sheep IgG (control). Six control kidneys excreted 176 +/- 31 micrograms/min of BSA initially, rising to 296 +/- 111 micrograms/min at 2 h. Fractional clearance of BSA rose from 0.51 to 1.70%. Eight experimental kidneys excreted 211 +/- 56 micrograms/min of BSA, increasing to 1,924 +/- 804 micrograms/min at 2 h. Fractional BSA clearance increased from 0.56 to 11.49%. After 60 min, BSA excretion in anti-GBM-perfused kidneys exceeded controls by a factor of 6.5-7.9 (P less than 0.05) and fractional BSA clearance exceeded controls by a factor of 5.8-7.1 (P less than 0.05). Studies with fluorescent markers indicated proteinuria to be of glomerular origin in antibody-perfused kidneys. There were no significant differences between anti-GBM-perfused and control kidneys in perfusion pressures, perfusate flow rates, urine flow rates, inulin clearance, or sodium reabsorption. Antibody to GBM can induce a marked increase in glomerular permeability to BSA and IgG without participation of other systemic humoral or cellular mediation systems.

Influence of antigen distribution on the mediation of immunological glomerular injury

To determine if the site of immune reaction could influence the mediation and morphological expression of glomerular injury in experimental anti-glomerular basement membrane (anti-GBM) nephritis and membranous nephropathy, we studied the events that followed the in situ reaction of rat antibody with antigen planted in either the GBM (especially the lamina rara interna) or in the subepithelial space (SE). Non-nephritogenic amounts of noncomplement-fixing sheep anti-GBM or anti-tubular brushborder antibody were injected into separate groups of rats to plant sheep IgG in the GBM and SE, respectively. Kidneys containing sheep IgG were then transplanted into naive recipients that were passively immunized with rat anti-sheep IgG. There was marked proteinuria after 2 days (antigen in GBM: 226 +/- 50.7; antigen in SE: 69 +/- 50.7 mg/24 hr) that was abrogated by prior depletion of complement in both groups (antigen in GBM: 10.2 +/- 1.7; antigen in SE: 14.3 +/- 8.7 mg/24 hr). When antigen was planted in SE, inflammatory-cell depletion with either anti-neutrophil (PMN) serum or lethal irradiation had no effect on proteinuria. In contrast, anti-PMN abolished proteinuria (12.0 +/- 5.6 mg/24 hr) and irradiation reduced it by 60% when antigen was in GBM. Glomeruli of kidneys with antigen in GBM were significantly larger and more hypercellular than those with antigen in SE after transplantation into immunized recipients. Endothelial cell injury and adherence of inflammatory cells to denuded GBM were prominent in the former (antigen in GBM), while glomeruli with antigen in SE showed only subepithelial deposits, adjacent slit-diaphragm displacement, and epithelial cell foot-process effacement. Thus, the reaction of antigen and antibody in glomeruli produced complement-mediated injury which was cell-independent when complex formation occurred on the outer aspect of the GBM but was cell-dependent when the same reagents reacted more proximally to the circulation. We therefore conclude that antigen distribution can critically influence the mediation and morphologic expression of immune glomerular injury and may, in part, account for variations in the clinical and histological manifestations of antibody-induced glomerular disease in humans.

Role of terminal complement pathway in the heterologous phase of antiglomerular basement membrane nephritis

Terminal complement components, including the membrane attack complex, have been demonstrated in glomeruli of patients with immune complex and anti-GBM nephritis. We recently demonstrated the functional significance of C6 in the mediation of experimental membranous nephropathy in rabbits. In the present study, the role of C6 was examined in the heterologous phase of rabbit anti-GBM nephritis by studying normal and C6-deficient (C6D) rabbits. In C6D rabbits, C6 hemolytic activity was less than 0.01% of control. All control rabbits became heavily proteinuric in the first 24 hr following injection of a standard dose of sheep anti-rabbit GBM antibody (mean, 42.0 +/- 26.3; range, 18.4 to 83.5 mg protein/mg creatinine, N = 5). In contrast, C6D rabbits excreted a mean of only 5.1 +/- 5.5 mg/mg creatinine (range, 0.06 to 14.4, N = 6, P = 0.002). Protein excretion in normal rabbits was less than 0.06 mg/mg creatinine. Both control and C6D rabbits had similar deposits of sheep anti-rabbit GBM IgG in glomeruli when measured by radiolabeling techniques (control 15.8 +/- 2.71, N = 5; C6D 18.7 +/- 1.99 micrograms of sheep IgG/10(4) glomeruli, N = 6, P greater than 0.05). Control rabbits had a greater rise in serum creatinine in the first 24 hr (1.74 +/- 1.15 vs. 0.53 +/- 0.44 mg/dl, P less than 0.05). Both groups had similar deposits of sheep IgG and rabbit C3 by IF. By light microscopy at 4 and 24 hr, both groups had qualitatively similar proliferative changes and similar numbers of neutrophils infiltrating glomeruli.(ABSTRACT TRUNCATED AT 250 WORDS)

Anuric renal failure precipitated by indomethacin and triamterene

We report a patient with compensated congestive heart failure who developed acute anuric renal failure immediately after indomethacin and triamterene had been added to the treatment regimen. Renal function failed to improve promptly with discontinuation of these medications, anuria persisting for 11 days. While it is well known that patients suffering from edematous states are prone to develop renal insufficiency when given nonsteroidal anti-inflammatory agents, it is not generally appreciated that the specific combination of prostaglandin inhibitors with triamterene may carry a particularly high risk of acute renal failure, even in euvolemic subjects.

Effect of antibody charge and concentration on deposition of antibody to glomerular basement membrane

Fixed anionic sites within the glomerular capillary wall influence the permeation of serum proteins, the localization of various antigens, and the deposition of antibody in the subepithelial space. In anti-GBM nephritis antibody deposition occurs very rapidly to antigenic sites located relatively proximal in the glomerular capillary wall. We examined the influence of the glomerular charge barrier on anti-GBM antibody deposition by comparing the rate of deposition of antibodies with cationic and anionic isoelectric points. Purified sheep anti-rat GBM IgG was isolated from acid eluates of kidneys obtained 24 hr after rats were injected with sheep antiserum to rat GBM. Anti-GBM IgG was separated into cationic (pI 6.4-8.5) and anionic (pI 4.2-6.8) fractions, which were radiolabelled with 131I and 125I, respectively, shown to have equal antibody contents measured by in vitro binding to normal glomeruli, mixed in equal amounts, and injected in incremental doses to ten rats. At 1 hr the glomerular antibody binding of each fraction was directly related to the blood level (r = 0.95, r = 0.97) and delivery of antibody (r = 0.98, r = 0.98). Glomerular binding of cationic antibody was four times greater than anionic antibody over the entire range of deliveries studied (P less than 0.001). We conclude that glomerular deposition of anti-GBM antibody is directly related to blood concentration and delivery of antibody. Furthermore, the deposition of cationic antibodies to GBM antigens was significantly greater than the deposition of anionic antibodies. The charge-selective glomerular filtration barrier may be an important determinant of the quantity and subclass composition of anti-GBM IgG deposits in glomeruli, and therefore of the severity of tissue injury produced.

Role of the terminal complement pathway in experimental membranous nephropathy in the rabbit

Our recent observations of a complement-mediated, cell-independent mechanism of altered glomerular permeability in rat membranous nephropathy suggested a possible role for the terminal complement pathway in the mediation of proteinuria in certain forms of glomerular disease. To directly determine whether the membranolytic terminal complement components (C5b-C9) are involved in glomerular injury, we studied the development of proteinuria in normal and C6-deficient (C6D) rabbits, in both of which a membranous nephropathy-like lesion develops early in the course of immunization with cationized bovine serum albumin (cBSA) (pI 8.9-9.2). C6 hemolytic activity of C6D was 0.01% that of control rabbits. After 1 wk of daily intravenous injections of cBSA, proteinuria developed in 71% of controls (median 154, range 1-3,010 mg/24 h, n = 24), whereas none of C6D were proteinuric (median 6, range 2-12 mg/24 h, n = 12, P less than 0.01). After 1 wk of cBSA, both groups had qualitatively identical glomerular deposits of BSA, rabbit IgG, and C3 on immunofluorescence microscopy, predominantly subepithelial electron-dense deposits on electron microscopy, and minimal glomerular inflammatory cell infiltration of glomeruli. Glomeruli were isolated from individual animals after 1 wk of cBSA and deposits of rabbit IgG antibody were quantitated by a standardized in vitro assay using anti-rabbit IgG-125I. Rabbit IgG deposits were found to be similar in control (29.8 +/- 13.2, range 12.7-48.6 micrograms anti-IgG/2,000 glomeruli, n = 6) and C6D rabbits (32.6 +/- 13.8, range 16.8-48.8 micrograms anti-IgG/2,000 glomeruli, n = 5, P greater than 0.05). After 2 wk, coincident with a prominent influx of mononuclear cells and neutrophils, proteinuria developed in C6D rabbits. These results document, for the first time, a requirement for a terminal complement component in the development of immunologic glomerular injury. Since the only known action of C6 is in the assembly of the membrane attack complex, these observations suggest that the membranolytic properties of complement may contribute to glomerular damage.

Specific uptake of Heymann's nephritic kidney eluate by rat kidney: studies in vivo and in isolated perfused kidneys

Antiglomerular antibodies have recently been found in immunoglobulin eluted from kidneys of rats with Heymann's nephritis. To demonstrate a role for these antibodies in the pathogenesis of Heymann's nephritis, paired-label radioisotope studies were used in the current study to quantitate binding of the eluted antibody to glomeruli of isolated perfused rat kidneys. In this perfusion situation, which largely excludes the formation of circulating immune complexes, specific binding of 0.9 to 3.2 per cent of the total eluate protein infused was found with 9 to 33 per cent of the bound protein recovered in the glomerular fractions. Specific glomerular binding was also observed after administration of the paired-label mixture to intact rats. Glomerular immunoglobulin deposits and subepithelial electron-dense deposits similar to those found in rats with Heymann's nephritis were produced by intravenous administration of the eluted antibody. Direct bonding of antibody to glomerular capillary wall antigens, in the manner similar to that established for antiglomerular basement membrane antibody, must be considered in the immunopathogenesis of Heymann's nephritis and potentially in some forms of human glomerular injury as well.