Altered glomerular permeability induced by F(ab')2 and Fab' antibodies to rat renal tubular epithelial antigen

Rats injected with F(ab')2 and Fab' antibody fragments directed against an antigen in the rat proximal tubular epithelial brushborder (Fx1A) developed immediate proteinuria [F(ab')2 43.2 +/- 6.7, N=6; Fab' 9.5 +/- 2.8, N=5; normal 1.6 +/- 0.9 mg/day, N=20]), that subsided after 3 to 5 days' duration. This reaction is in contrast to one exhibited by rats given intact IgG anti-Fx1A; the rats that did not develop immediate proteinuria (2.2 +/- 0.3 mg/day, N=5), and the glomerular binding of 125I-antibody fragments was significantly less than that of intact IgG [F(ab')2 0.11 +/- 0.01; Fab' 0.03 +/- 0.01; IgG 0.17 +/- 0.01% administered equimolar dose] at 24 hr. No proteinuria resulted from equimolar doses of nonantibody F(ab')2 and Fab'. Less than 8% of the proteinuria induced by antibody fragments represented injected material, and 30 to 38% was albumin. Immunofluorescence revealed faint and diffuse glomerular capillary wall deposits of F(ab')2 and Fab' and tubular brushborder staining. Subepithelial, electron-dense deposits and focal, podocyte effacement were seen by electron microscopy in rats given the F(ab')2 antibody. Light microscopy and colloidal iron-staining were normal. In our study antibody fragments appear to interact directly with components of the outer, glomerular capillary wall to alter permeability in the absence of recognized mediators such as complement and inflammatory cells.

A new role for complement in experimental membranous nephropathy in rats

The only established role for complement in mediating immunologic renal disease involves elaboration of leukochemotactic factors and neutrophil-dependent glomerular injury. In the passive Heymann nephritis (PHN) model of experimental membranous nephropathy, rats injected with sheep antibody to rat proximal tubular brush border antigen (Fx1A) form subepithelial deposits of sheep IgG and rat complement (C3), and develop heavy proteinuria after 5 d without glomerular inflammatory changes. To study the role of complement in mediating proteinuria in PHN, 16 rats were treated daily with cobra venom factor from before antibody injection to maintain C3 levels at < 10% of pretreatment values and compared to 16 untreated controls. Proteinuria at 5 d was abolished in C3-depleted rats (4 +/- 1, controls 70 +/- 15 mg/d, P < 0.001), although renal deposition of 125I-labeled antibody ws the same in both groups (188 +/- 35 vs. 191 +/- 22 microgram IgG/2 kidneys, P > 0.5). Nephritogenic doses of both the noncomplement-fixing F(ab')2 portion and the gamma 2 subclass of anti-Fx1A IgG produced subepithelial deposits of immunoglobulin without C3, but proteinuria did not occur despite glomerular deposition of up to 70 microgram/2 kidneys of gamma 2. However, glomerular deposition of as little as 60 microgram of gamma 1 produced C3 fixation in vivo and heavy proteinuria. No neutrophil exudate could be detected histologically in PHN from the time of antibody injection through development of proteinuria. Proteinuria in five PHN rats depleted of neutrophils to < 200/mm3 with antineutrophil serum was not reduced compared to six controls with normal neutrophil counts (34 +/- 9.6 vs. 25 +/- 10.4 mg/d, P > 0.5). These results demonstrate that proteinuria in the PHN model of membranous nephropathy is complement-dependent and strongly suggest a neutrophil-independent mechanism. Thus a new role for the complement system in mediating immunologic glomerular injury is identified.

Experimental membranous glomerulonephritis in rats. Quantitative studies of glomerular immune deposit formation in isolated glomeruli and whole animals

Quantitation of immune deposit formation in glomeruli and correlation with immunohistologic and functional changes has been accomplished only in models of anti-glomerular basement membrane antibody-induced nephritis, or indirectly in immune complex disease by measuring radiolabeled antigen deposition. The kinetics of subepithelial immune deposit formation and the relationship between the quantity of antibody deposited and proteinuria are defined here for the first time in an established model of membranous immune complex nephritis (passive Heymann nephritis) induced by a single intravenous injection of (125)I-labeled sheep immunoglobulin (Ig)G antibody to rat tubular brush border antigen (Fx1A). Measurement of antibody deposition in glomeruli (GAb) isolated from rats injected with 10 mg of anti-Fx1A demonstrated a mean of 12 mug GAb in 4 h, which increased linearly to 48 mug in 5 d. GAb represented only 20 and 44% of total kidney antibody binding at these times. Proteinuria occurred only after 4-5 d of antibody deposition in rats with total kidney antibody binding exceeding approximately 200 mug/2 kidneys. Steroid treatment and vasoactive amine blockade did not significantly alter the quantity or localization of immune deposits. It was also demonstrated that isolated rat glomeruli specifically bound nephritogenic quantities of anti-Fx1A in vitro within hours. Analysis of the quantitative aspects of glomerular antibody deposition in vivo and glomerular antibody binding in vitro provides additional evidence that subepithelial immune deposits in passive Heymann nephritis may form in situ by reaction of free antibody with antigenic constitutents of the normal rat glomerulus. The observed kinetics of deposit formation differ markedly from those in anti-glomerular basement membrane disease and suggest a role for factors in addition to antigen-antibody interaction in determining this unique pattern of glomerular immune deposit formation.

Determinants of glomerular localization of subepithelial immune deposits: effects of altered antigen to antibody ratio, steroids, vasoactive amine antagonists, and aminonucleoside of puromycin on passive Heymann nephritis in rats

The role of circulating immune complex deposition versus in situ complex formation in membranous nephropathy is controversial. Passive Heymann nephritis in rats resembles membranous nephropathy in man and was induced by injection of sheep antibody to rat proximal tubular epithelial cell brush border antigen (anti-Fx1A). Minutes after injection of 1 ml. of anti-Fx1A, subepithelial immune deposits were seen by immunofluorescence and electron microscopy, and proteinuria appeared within 5 days. The effects of alterations in the dose of administered antibody, corticosteroid therapy, and vasoactive amine blockade on the development of subepithelial deposits and consequent proteinura were studied. Variation of the dose of anti-Fx1A from 0.25 ml. to 1 ml. resulted in a progressive increase in the size and number of glomerular capillary wall deposits, but no alterations in their distribution. Only those rats which received 1 ml. became proteinuric within 5 days. Corticosteroid therapy and vasoactive amine blockade, begun 24 hours prior to the induction of passive Heymann nephritis and continued until termination of the study 5 days later, had no effect on the amount or site of immune complex formation, nor on the extent of proteinuria as compared to untreated controls. In contrast, in rats with unilateral proteinuria produced by the selective perfusion of one kidney with aminonucleoside of puromycin 7 days prior to the induction of passive Heymann nephritis, there was a marked reduction of subepithelial deposits in the perfused kidney as compared to the nonperfused contralateral kidney. In this model of membranous nephropathy, systemic factors play little role in the development of subepithelial deposits, whereas local factors are critical. These findings are consistent with the hypothesis that subepithelial immune deposits form locally.

Experimental glomerulonephritis in the isolated perfused rat kidney

The development of immune deposits on the subepithelial surface of the glomerular capillary wall was studied in isolated rat kidneys perfused at controlled perfusion pressure, pH, temperature, and flow rates with recirculating oxygenated perfusate containing bovine serum albumin (BSA) in buffer and sheep antibody to rat proximal tubular epithelial cell brush border antigen (Fx1A). Control kidney were perfused with equal concentrations of non-antibody immunoglobulin (Ig)G. Renal function was monitored by measuring inulin clearance, sodium reabsorption, and urine flow as well as BSA excretion and fractional clearance. Perfused kidneys were studied by light, immunofluorescence, and electron microscopy. All kidneys perfused with anti-Fx1A developed diffuse, finely granular deposits of IgG along the glomerular capillary wall by immunofluorescence. Electron microscopy revealed these deposits to be localized exclusively in the subepithelial space and slit pores. Similar deposits were produced in a nonrecirculating perfusion system, thereby excluding the formation of immune complexes in the perfusate caused by renal release of tubular antigen. Control kidneys perfused with nonantibody IgG did not develop glomerular immune deposits. Renal function and BSA excretion were the same in experimental and control kidneys. Glomerular deposits in antibody perfused kidneys were indistinguishable from deposits in rats injected with anti-Fx1A or immunized with Fx1A to produce autologous immune complex nephropathy. These studies demonstrate that subepithelial immune deposits can be produced in the isolated rat kidney by perfusion with specific antibody to Fx1A in the absence of circulating immune complexes. In this model deposits result from in situ complex formation rather than circulating immune complex deposition.

Evaluation of 125I-DNA for detecting anti-DNA antibodies in the diagnosis of systemic lupus erythematosus

A 125I-DNA preparation for the detection of human anti-DNA antibodies (ADA) was evaluated as a diagnostic test for systemic lupus erythematosus (SLE). A normal range of 0-25 U/ml was established. Serum ADA level greater than 110 U/ml were diagnostic in clinically active SLE and levels greater than 45 U/ml were found in 75% of patients with inactive disease. This value was significantly greater than that found in rheumatoid arthritis, renal disease caused by non-immune mechanisms, post-streptococcal glomerulonephritis and a miscellaneous group of disorders comprising connective tissue diseases, auto-immune disorders and chronic active hepatitis. Anti-nuclear factor (ANF) titres greater than 1/160 and LE cells were found in 85% of these patients. In inactive disease the ADA levels ranged between 25 and 98 U/ml, ANF titres varied from 1/40 to 1/640, and LE cells were detected in only 20% of the cases. In 3 patients investigated during the course of the disease, the ADA levels correlated best with clinical improvement. Two patients with apparent active lupus nephritis showed intermediate ADA levels, which were probably caused by antigen-antibody formation and immune complex deposition in the kidneys.

Depressed neutrophil chemotaxis in patients with chronic renal failure and after renal transplantation

Polymorphonuclear leukocyte chemotaxis, phagocytosis, and bactericidal ability were tested with neutrophlis from patients with chronic renal failure on conservative therapy, from others of regular peritoneal dialysis or hemodialysis, and from a group of patients who had received renal allografts. Chemotaxis was depressed in all groups. Phagocytosis was mildly impaired in the two groups on dialysis. The leukocytes of patients on conservative therapy had mildly decreased killing ability, whereas this function was normal in other groups tested. Sera from all patients, when activated with endotoxin, were poorly chemotactic to normal neutrophils, especially in those on conservative therapy and hemodialysis, but these sera functioned normally as opsonins for phagocytosis. The observed defect in chemotaxis could account, at least partly, for the frequency of bacterial infections in these patients.

Cross-matching assays of cell-mediated immunity for transplant patients

Assays of cell-mediated immunity before transplantation were performed on 34 patients who were defined as being at high risk by the presence of preformed lymphocytotoxic antibodies and/or HL-A incompatibilities at FOUR locus. Assays for cell-mediated lympholysis type I (cml I) were performed in donor serum, and for CML II in recipient serum, to assess the possible effect of blocking factors in the patients' sera. A positive (greater than 5% specific Cr release) and in particular a greater than 10% Cr release correlated strongly with graft rejection. The correlation between CML II and graft survival was unimpressive. No clinically beneficial blocking factor was demonstrable in the patients's sera in that 5 of 6 patients with a positive CML I but a negative CML II rejected their grafts. Conversely, 6 of 8 patients with a positive CML II and a negative CML I had excellent long-term courses. The use of CML I assay in the selection of grafts for patients at high risk is recommended.

Hyperlipidaemia in renal transplant patients

The prevalence, nature and possible aetiology of post-transplantation hyperlipidaemia were studied in 94 renal allograft recipients. Sixty-five per cent of the group had hypercholesterolaemia or hypertriglyceridaemia, and types IIb and IV were the commonest forms of hyperlipoproteinaemia encountered. The pathogenesis of post-transplantation hyperlipidaemia is complex. Hypertriglyceridaemia was maximal in the first year after transplantation and could be correlated with high corticosteroid dosage during this period. Thereafter hypertriglyceridaemia was less marked and was related to obesity, corbohydrate intolerance and basal insulin levels. Mean cholesterol levels were elevated throughout the post-transplantation period, varied little and could not be related to corticosteroid dosage, body weight, carbohydrate intolerance, basal insulin levels or renal dysfunction.

Angiography after renal homotransplantation

The role of angiography in the investigation of problems encountered among 181 patients who received renal transplants at the Johannesburg General Hospital is analysed. In all, 23 patients underwent arteriography or venography after transplantation for the investigation of problems such as renal dysfunction, hypertension and suspected renal vein or iliofemoral venous thrombosis.

Coagulation studies in long-term survivors after renal allograft transplantation

Screening coagulation studies were carried out on 69 long-term survivors who had received renal allografts. Fibrinogen levels were significantly raised in this group. Factor VIII activity was increased in 7 of the 11 patients studied. Six long-term survivors of renal allografts demonstrated arterial thrombotic phenomena. The onset of the thrombotic episode occurred at a relatively young age. It is considered that the hypercoagulable state may contribute to the observed increased tendency towards arterial thrombotic phenomena.

Pregnancy in renal transplant recipients

Of the 48 female patients attending the outpatient clinic of the Johannesburg General Hospital Transplant Unit between January 1971 and December 1974, 10 became pregnant. Fifteen pregnancies were recorded, 6 of which ended in abortions. Ten infants were born from the remaining 9 pregnancies and 4 (40%) died in the neonatal period. The main cause of neonatal death was prematurity. One major congenital anomaly, a diaphragmatic hernia, was found. Maternal complications were mild and easily controlled, urinary infection being the commonest. One patient showed a moderate reduction in renal function. Obstruction of labour by the transplanted kidney was not encountered, and the two Caesarean sections were performed for obstetrical reasons unrelated to the renal transplant.

An unusual hormonal cause of hypertension and hypokalaemia

A patient with primary hyperparathyroidism who presented with hypokalaemia and hypertension is described. Renal potassium wasting was documented and cured by removal of a parathyroid adenoma. Possible mechanisms for this unusual manifestation of hyperparathyroidism are mentioned. Other features of the case were severe anaemia, nephrocalcinosis, pseudogout and postoperative acidosis.