Familial C4B deficiency and immune complex glomerulonephritis.

Homozygous complement C4B deficiency is described in a Southern European young female patient with Membranoproliferative Glomerulonephritis (MPGN) type III characterized by renal biopsies with strong complement C4 and IgG deposits. Low C4 levels were independent of clinical evolution or type of immunosuppression and were found in three other family members without renal disease or infections. HLA typing revealed that the patient has homozygous A*02, Cw*06, B*50 at the class I region, and DRB1*08 and DQB1*03 at the class II region. Genotypic and phenotypic studies demonstrated that the patient has homozygous monomodular RCCX in the HLA class III region, with single long C4A genes coding for C4A3 and complete C4B deficiency. Her father, mother, son and niece have heterozygous C4B deficiency. The patient's deceased brother had a history of Henoch-Schönlein Purpura (HSP), an immune complex-mediated proliferative glomerulonephritis. These findings challenge the putative pathophysiological roles of C4A and C4B and underscore the need to perform functional assays, C4 allotyping and genotyping on patients with persistently low serum levels of a classical pathway complement component and glomerulopathy associated with immune deposits.

Urine N-acetyl-beta-D-glucosaminidase--a marker of tubular damage?

BACKGROUND: Although an indicator of renal tubular dysfunction, an increased urinary N-acetyl-beta-D-glucosaminidase (NAG) activity might reflect increased lysosomal activity in renal tubular cells. METHODS: Puromycin aminonucleoside (PAN) was administered to Sprague Dawley rats to induce proteinuria. Total protein, albumin, NAG activity and protein electrophoretic pattern were assessed in daily urine samples for 33 days. The morphological appearance of the kidneys was examined on days three, four, six, eight and thirty three and the NAG isoenzyme patterns on days zero, four, eight and thirty three. RESULTS: Following intravenous PAN urine volume and urine NAG activity increased significantly by day two, but returned to normal by day four. After day four all treated animals exhibited a marked rise in urine albumin, total protein excretion and NAG activity. Electrophoresis showed a generalised increase in middle and high molecular weight urine proteins from day four onwards. Protein droplets first appeared prominent in tubular cells on day four. Peak urine NAG activity and a change in NAG isoenzyme pattern coincided with both the peak proteinuria and the reduction in intracellular protein and NAG droplets (day six onwards). CONCLUSIONS: This animal model demonstrates that an increase in lysosomal turnover and hence urine NAG activity, occurs when increased protein is presented to the tubular cells. Urine NAG activity is thus a measure of altered function in the renal tubules and not simply an indicator of damage.

Progressive glomerular toxicity of ifosfamide in children.

Glomerular toxicity following ifosfamide (IFO) is not as well recognized as renal tubular damage. Following a case of ifosfamide-induced renal failure with histological evidence of glomerular changes, we undertook a retrospective study of all IFO-treated children to assess the extent and severity of its glomerular toxicity and to identify possible predisposing factors. Thirty-seven children with a follow-up of 6 months or more from the end of chemotherapy were studied. They were a median of 10.8 years old (range 3.25-18.5), had received a median of 54 g/m2 (range 9-135) of IFO, and had a median follow-up of 29 months (range 6-68). The criteria to identify glomerular dysfunction were raised plasma creatinine (Pc) values on two occasions or a low glomerular filtration rate (GFR) measured by Tc-99-DTPA clearance. Detailed assessment was carried out to identify other nephrotoxic influences in these children. Subjects in whom glomerular dysfunction could be causally linked to IFO were compared with the rest of the group for a variety of predisposing factors. Of eight children with glomerular dysfunction, two had other nephrotoxic influences and were excluded from further analysis. In six (17.1%) children, glomerular dysfunction appeared to be causally linked to IFO. Their median GFR was 61.9 ml/min/1.73 m2(range 33-85) and Pc was 123 mumol/l (range 85-216). Five of the six had normal glomerular function at the end of therapy and the raised Pc values were first noted 19, 21, 26, 29, and 36 months later. Children with glomerular toxicity had a significantly longer median follow-up (41.5 vs. 19 months; P = 0.04) than the rest of the group, suggesting late onset of this problem. They were older at the time of the study and had received nearly twice the dose of IFO, though the differences in age and dose did not reach statistical significance. The earliest signs of renal toxicity were seen in the index case, who had had prior nephrectomy. All affected children had coexistent and preceding tubular toxicity. The inadequacies of tests commonly used to assess glomerular function and the possibility of underestimation of dysfunction are discussed. Glomerular dysfunction following IFO is poorly recognized and evidence from this study of its later onset and progressive nature is a cause for concern. The index case is described with histological findings.

Alterations of glomerular basement membrane charge and structure in diabetic nephropathy.

We examined glomerular basement membrane anionic site distribution identified by cationic gold in seven patients with insulin-dependent and four patients with non-insulin-dependent diabetes mellitus, presenting a spectrum of clinical and glomerular changes. Anionic sites were investigated by pretreatment of tissue with glycosaminoglycan-degrading enzymes prior to cationic gold staining. The distribution of chondroitin sulphate proteoglycans--a previously unrecognized glomerular basement membrane component--and type IV collagen was examined by immunoelectron microscopy to identify structural changes in the basement membrane. Findings were compared with those of non-diabetic patients showing minor proteinuria and morphologically normal glomerular basement membranes. Two patients, originally diagnosed as having diabetic nephropathy were also examined at 19 weeks and 5 years after renal transplantation. Characteristic redistribution of type IV collagen and chondroitin sulphate proteoglycans was noted in thickened glomerular basement membrane segments (> 400 nm) of diabetic patients and those with renal transplants. Extension of anionic sites deep into the glomerular basement membrane at pH 2.5, together with loss of interna sites at pH 5.8 is unique to diabetic nephropathy. Reduced charge density was apparent in some patients due to thickening of the glomerular basement membrane, although the number of anionic sites per unit length of membrane was actually increased. Thus, charge aberration in diabetic nephropathy is due to displacement rather than loss of anionic sites. Removal of more than 90% of these sites by heparitinase, confirms their association with heparan sulphate proteoglycans. Similar derangement of anionic sites in all patients with diabetic nephropathy irrespective of the degree of proteinuria, suggests that a heparan sulphate proteoglycan-related charge barrier plays a minor role in controlling permeability of the diabetic glomerular basement membrane.

Cationic gold staining of glomerular anionic sites in archived tissue, reprocessed from paraffin wax into LR gold resin.

Glomerular capillary wall anionic sites have been demonstrated by cationic gold staining of archived renal biopsy tissue (up to 10 years old), obtained from six patients, originally embedded in paraffin wax, and subsequently reprocessed into LR gold resin. The staining patterns at pH 2.5 and pH 7.0, demonstrating different glomerular basement membrane (GBM) anionic constituents, were compared in three patients from whom tissue directly processed into LR gold and reprocessed tissue was available. Ultrastructural preservation was poorer and shrinkage artefact greater in paraformaldehyde-lysine periodate (PLP) as opposed to formol saline-fixed reprocessed tissue. However, GBM anionic site expression was well preserved, or even enhanced (lamina rara externa, pH 7.0) in reprocessed tissue, using either fixative. Although it may not be possible to compare subtle changes in anionic site distribution in variously fixed and processed tissues, due to these artefacts, the technique enables retrospective study of charge status in archived material from disease groups in which there are distinct anionic site aberrations.

Cationic colloidal gold--a novel marker for the demonstration of glomerular polyanion status in routine renal biopsies.

Investigations of glomerular anionic charge status in human renal biopsies have previously been restricted, by the techniques and markers used, to staining of sites in pre-embedded tissue. The introduction of a novel marker, cationic colloidal gold, which demonstrates fixed anionic sites in hydrophilic resin (LR Gold)-embedded, ultrathin tissue sections, has now enabled glomerular charge to be evaluated in routine biopsy material. The cationic gold marker detects components which express anionic charge under different pH conditions. The patterns of staining in tissue showing minor glomerular pathology and low proteinuria, together with enzyme-digestion studies indicate that anionic sites are normally associated with heparan sulphate proteoglycans, glycocalyx sialoproteins, hyaluronic acid, and other GBM components which have not yet been characterised. Several charge aberrations involving different pathological mechanisms have been identified using cationic gold. These aberrations may be categorised according to the pathological basis of the charge pattern defect, rather than glomerular disease classification, as a prelude to the precise identification of the anionic sites and their functional importance in relation to the glomerular charge selectivity barrier. The categories which have been defined are: (1) 'Normal', (2) interrupted, (3) neutralised, (4) structurally disorganised, and (5) depleted. As sites are further characterised sub-categorisation is likely. We anticipate that this approach will help to elucidate both the participation of charged components in disease pathogenesis and their role in relation to glomerular proteinuria.

An ultrastructural morphometric study of membranous glomerulonephritis.

Sixteen cases of membranous glomerulonephritis and 17 controls were studied using electron microscopy and morphometry of whole glomerular cross-sections. It was found that, in relation to controls, in membranous glomerulonephritis the following parameters are increased: total area, total number of cells, all basement membrane parameters, visceral epithelium compartment area and visceral epithelial cell area, area of parietal epithelium, mesangium and urinary space, number of endothelial and mesangial cells; by contrast, the following are decreased: number of visceral epithelial cells, capillary and endothelial volume fractions. Correlation analysis between morphometric and clinical parameters demonstrated significant correlations between capillary basement membrane thickening and duration of disease, proteinuria and renal function; the changes in visceral epithelial cells correlated with serum albumin, proteinuria and inverse of creatinine; changes in relative area of capillary lumina correlated with blood pressure. It is concluded that the ultrastructural morphometric study of renal biopsies will lead to better understanding of glomerular disease.

Uptake and disposal of BSA-coated latex particles by the rat mesangium: reaction with subsequently administered heterologous antiserum.

Mesangial uptake and disposal of antigen-coated latex particles and the ability of subsequently injected antibody to maintain complexed antigen in the rat mesangium has been investigated. Carboxylate-modified latex particles, coated with bovine albumin (BSA) were injected i.v. to 36 Wistar rats. Twenty-two rats (group 1) were not treated further. Fourteen rats (group 2) received rabbit anti-BSA antiserum i.v. and i.p. 24 h later. Control groups were injected with uncoated, unmodified latex particles or soluble BSA with and without subsequent antibody administration. Latex was present in the mesangial matrix of rats in group 1 at 1 h in association with a diffuse mesangial distribution of BSA. At 24 h, BSA staining was markedly reduced and extracellular latex was no longer observed. Intracellular latex aggregates were present in experimental and control groups at 24 h-14 days in cytoplasmic vacuoles of hypertrophic mesangium which showed minor infiltration by macrophage-like cells. Progressive removal of latex aggregates coincided with declining mesangial reactivity. Rapid disappearance of antigen apparently results from local degradation of tracer in the mesangium. Antibody administration preserves BSA in the mesangium due to immune complex formation and is associated with retention of ingested latex by mesangial cells. However, efficient disposal of glomerular immune deposits by the mesangium appears to minimize infiltration by monocytes and prevents aggravation of glomerular inflammation.

Comparison of in vitro demyelination and cytotoxicity of humoral factors in multiple sclerosis and other neurological diseases.

The distribution and nature of serum factors causing in vitro demyelination and glial lysis were investigated in multiple sclerosis (MS), other neurological diseases (OND), ill control and control groups. MS sera were unique in affecting only CNS myelin and glia whereas stroke and Guillain-Barré syndrome (GBS) sera brought changes to both CNS and PNS tissue. Through both visual scoring of myelin damage and the quantitative measurement of radiolabel release from cerebellar cultures, it was evident that the MS and OND groups have similar myelino- and cytotoxic effects. This may reflect MS and OND sera sharing similar humoral factors. 74% MS, 68% OND and 22% of control scores were above a score threshold designed to exclude culture handling trauma effects. When classified by their current disease state MS patients with severe and mild disease yielded higher in vitro scores than did those with moderate disease who comprised an older age group. No other clinical features of MS patients gave any association with in vitro serum effects. The rare demonstration of bound Fab IgG in cultures after MS serum tests indicates that immune mechanisms are unlikely to make a large contribution to serum-induced demyelination and cellular change in vitro.

Renal tubular epithelia ultrastructure in autolysis.

Post-mortem changes in the proximal and distal tubules of rat kidneys left in situ have been studied at the light microscope and ultrastructural levels. The distal tubular nuclei showed distinct changes which were completely different from the usual nuclear appearances after death and resemble the changes seen in apoptosis. These observations suggest that the unusual changes in the autolytic distal tubular nuclei may be due to the activation of endogenous endonucleases.

Retrospective study of histological features of acute rejection in renal allografts and comparison with circulating T cell populations.

The histological severity of acute rejection in renal allografts was determined for 39 rejection episodes in 30 renal transplant recipients. Data were compared with the peripheral blood T cell subset ratios measured before and at the onset of the rejection episode. T cell subset ratios showed no correlation with the histological severity of rejection, nor with the reversibility of the rejection episode. The grade of histological rejection on biopsy was predictive of graft survival. We conclude that renal biopsy remains the best method for determining the severity and outcome of acute allograft rejection episodes.

Long term prognosis of recurrent haematuria.

A long term follow up study of 100 children referred with recurrent haematuria for at least one year to two regional paediatric nephrology units is described. The mean duration of follow up was 8.2 years. An adequate renal biopsy was obtained in 96 and eight cases of Alport's syndrome and 10 of IgA nephropathy were diagnosed (20% and 26% respectively of the biopsies examined by electron microscopy and immunofluorescence). Five patients developed end stage renal failure and six hypertension requiring treatment, with the occurrence of these complications increasing progressively with increasing duration of follow up (1% at five years compared with 12% at 10 years). Adverse prognostic features were persistence of microscopic haematuria, proteinuria at presentation, and appreciable changes on renal biopsy. Eighty four patients had first degree relatives tested for haematuria; 30% of these families had another affected member. With long term follow up recurrent haematuria is associated with considerable morbidity and potential mortality.

In vitro toxicity of MS sera correlates with new clinical signs.

In vitro toxicity of sera from 10 MS patients was followed for up to 3 years. Myelinotoxicity and cytotoxicity measured as radiolabel release from rat cerebellar explants were almost continuously higher in than in controls while peaks of radiolabel release were associated with the emergence of new clinical signs in the MS patients.

Persistence of inert macromolecules (Imposil) in the rat mesangium and glomerular functional disturbance.

Imposil iron-dextran is an inert tracer that has been used to study mesangial uptake and clearance of macromolecular material from the glomerular circulation. Such a tracer may be a useful marker of altered mesangial function in animals with some forms of glomerulonephritis. We have studied mesangial handling of intravenously injected Imposil (50 mg/100 g body weight) in normal rats by light, immunofluorescence and electron microscopy for up to 3 months. Mesangial cell uptake was maximal at 48-54 h. Extrusion and drainage of tracer to the vascular pole and distal tubule was evident at 3 days but iron was still present in mesangial cells at 3 months. Possible functional renal impairment resulting from persistent mesangially sequestered tracer was examined by measuring daily urine protein and iron excretion. A possible relationship between failure of mesangial cells to eliminate inert tracer and increasing glomerular permeability is demonstrated, suggesting that Imposil and similar inert macromolecules cannot be used for long-term studies of mesangial function.

The myelodysplastic syndromes--a study of haemostatic function and platelet ultrastructure.

The myelodysplastic syndromes (MDS) are characterised by dysplastic marrow and cytopenia. Clinically detectable bleeding is uncommon and usually attributed to thrombocytopenia. We have investigated some aspects of haemostatic function in 17 patients with MDS and compared the results with findings from 17 control patients matched for age and sex. No specific disorder of blood coagulation or fibrinolysis was identified. The main abnormalities observed in the patients were: prolongation of the bleeding time which was greater than could be explained on the basis of thrombocytopenia in 13 patients; absent, or severely impaired platelet aggregation in response to collagen in 7 patients; impaired platelet production of malondialydehyde when stimulated with collagen and abnormal release of 14C-5 hydroxytryptamine in 5 patients; and abnormalities of ultrastructure in all 5 patients whose platelets were viewed by electron microscopy.

Role of complement in demyelination in vitro by multiple sclerosis serum and other neurological disease sera.

Multiple sclerosis (MS) sera can demyelinate and cause selective cellular changes to organ cultures of rodent CNS which suggests possible immunoglobulin involvement. The complement dependence of this serum action was investigated using complement-inactivating agents and radiolabelled rat cerebellar cultures. After heat inactivation at 56 degrees C, the in vitro effects of MS, chronic relapsing experimental allergic encephalomyelitis (cr-EAE) and Guillain-Barré syndrome (GBS) sera were severely reduced or eliminated as measured by radiolabel release. On introducing a source of fresh complement, the cr-EAE and GBS serum effects were largely restored whereas MS serum effects remained suppressed. Inactivation of serum complement with mercaptoethanol and Zymosan was associated with marked reduction in serum myelinotoxicity; some restoration of in vitro effects was possible on adding fresh complement although this occurred to a greater extent with cr-EAE and GBS than with MS sera. Inactivation of the alternative complement pathway brought a limited reduction in MS serum activity in vitro which was not restored with fresh complement. It is concluded that complement is involved only to a limited extent in MS serum myelinotoxic effects and that MS serum effects in vitro are due to several components of which thermolabile substances make a significant contribution and are as yet uncharacterised.

New approach to study of in vitro toxicity of multiple sclerosis and other sera.

The in vitro effects of MS and control sera were quantified by the measurement of radiolabel released from myelinated cultures of rat cerebellum and compared with a visual assessment of myelin damage. Radiolabel release gave a sensitive index of serum effects in vitro which was free of the score assignment decisions that are associated with the visual assessment of myelin damage. Examination of the patterns of radiolabel release elicited by MS and control sera on cultures labelled with either L-[5-3H]tryptophan or galacto-D-[6-3H]cerebroside indicates that MS serum effects are not simply a stronger expression of the weak control serum effects.