Activated C3 (C3b) in the nephritic glomerulus

An autoradiographic technique was developed to assess in the nephritic glomerulus the relative amount of C3 which is in the activated form, C3b, compared with the inactivated form, iC3b. Frozen renal biopsy sections from children and young adults with glomerulonephritis were assessed for the C3b fraction of total C3, using a radiolabeled monoclonal anti-C3c. Grain counts with this antibody, before and after reacting the section with 0.0002% typsin, gave the relative amounts of total C3 and C3b, respectively. C3b was found in all diseases studied. To explain its presence, glomerular C3b acceptors which would restrict C3b inactivation were sought by immuno-fluorescence studies. C3b acceptor candidates were: igG in aggregated form, IgA as found in the IgA nephropathies and the C3/C5 convertase, C4b,2a,3b. In acute post-streptococcal glomerulonephritis and membranoproliferative glomerulonephritis type III, diseases in which these acceptors were lacking, it is postulated that the nephritis strain-associated protein and absence of membrane cofactor protein, respectively, may be responsible for C3b deposition. The phlogistic effect of C3b is mediated largely by one of its products, C5b-9. However, the C3b: total C3 ratio failed to correlate with indices of glomerular inflammation. probably in part because the ratio is not a measure of total glomerular C3b.     

Cystatin C as a marker for glomerular filtration rate in pediatric patients

Cystatin C is a non-glycated 13-kilodalton basic protein produced by all nucleated cells. The low molecular mass and the basic nature of cystatin C, in combination with its stable production rate, suggest that the glomerular filtration rate (GFR) is the major determinant of cystatin C concentration in the peripheral circulation. Recently published studies have shown that cystatin C correlates more strongly than creatinine with GFR measured using the ⁵¹Cr-EDTA clearance. The aim of this study was to evaluate serum cystatin C as a marker for GFR in children. GFR was determined on medical indications using the ⁵¹Cr-EDTA technique in pediatric patients (2–16 years) in our renal unit. Simultaneously their cystatin C and creatinine concentrations were also measured. Of our 52 patients, 19 had a reduced renal function (<GFR 89 ml/min per 1.73 m²) based on the ⁵¹Cr-EDTA clearance. The correlation of cystatin C with the isotopic measurement of GFR tended to be stronger (r=0.89, P=0.073) than that of creatinine (r=0.80). Receiver operating characteristic analysis showed that the diagnostic accuracy of cystatin C was better (P=0.037) than that of creatinine in discriminating between subjects with normal renal function and those with reduced GFR. This study demonstrates that serum cystatin C has an increased diagnostic accuracy for reduced GFR when compared with serum creatinine. Hence, cystatin C seems to be an attractive alternative for the estimation of GFR in children. Received: 13 May 1998 / Revised: 22 September 1998 / Accepted: 22 October 1998     

Decreasing hypocomplementemia and membranoproliferative glomerulonephritis in Japan

The number of patients with membranoproliferative glomerulonephritis(MPGN) diagnosed in our institution and the incidence of hypocomplementemia as determined by school urinary screening programs in Japan were investigated retrospectively. Fifty-seven children were diagnosed as having MPGN between 1974 and 1997. Of these, 13 patients were diagnosed during period 1 (1974–1979) and 25 during period 2 (1980– 1985). A decreasing trend was observed during periods 3 (1986–1991) (12 patients) and 4 (1992–1997) (7 patients) compared with period 2 (P<0.05 and P<0.01, respectively). A significant difference was also noted when MPGN was compared between periods 1 and 2 (1974– 1985) and periods 3 and 4 (1986–1997) (P<0.01). Serum C3 was measured in 1,282 school children with abnormal urinary findings between 1980 and 1997. Thirty children had hypocomplementemia. The incidence of hypocomplementemia was significantly lower in period 3 (1986–1991) (9 children) and period 4 (1992–1997) (2 children) compared with period 2 (1980–1985) (19 children) (P<0.05 and P<0.01, respectively). New cases of MPGN in our institution and the incidence of hypocomplementemia as determined by school urinary screening programs are decreasing in Japan. The reason for this trend is unknown. Received: 10 August 1999 / Revised: 22 November 1999 / Accepted: 23 November 1999     

Birth weight has no influence on glomerular number and volume

It has been proposed that low birth weight (LBW) results in a reduction in glomerular number that may, in turn, predispose an individual to develop hypertension in adulthood. Glomerular number is reduced in animal models of intra-uterine malnutrition using a variety of techniques. However, the relevance of such extreme models to man is uncertain. The purpose of this study was to evaluate whether animals with naturally occurring LBW, which have not received any manipulation in utero, have a reduction in glomerular number, altered glomerular volume and abnormal urine albumin excretion. Litters from female rats delivering at term on the same day were weighed and sexed at birth. From each litter 2 males with the lowest birth weight (LBW n=18) and 2 males with a birth weight closest to the litter mean [normal birth weight (NBW) n=18] were selected and cross-fostered onto periparturient lactating dams. LBW rats weighed 6.7±0.6 g compared with 7.2±0.6 g for NBW rats (P=0.03). After weaning all rats were weighed weekly and underwent metabolic studies at 4, 8, 12 and 16 weeks. Following perfusion fixation, glomerular number and mean glomerular volume were estimated using standard stereological techniques. There was no significant difference between LBW and NBW rats with respect to glomerular number (24 499±2 078 vs. 24 825±1 818), mean glomerular volume and urine albumin excretion, and no rats had a glomerular number outside the normal range. This study suggests that naturally occurring LBW has little influence on renal development, glomerular number and volume. Received: 29 August 2000 / Revised: 8 December 2000 / Accepted: 11 December 2000     

Vascular C3 deposits on renal biopsy in pediatric patients with hematuria

Isolated deposition of the third component of complement (C3) in the renal arterioles has been noted on biopsy specimens in patients with hematuria. This entity is of little known significance and reports of this finding in pediatric patients with hematuria are rare. We reviewed the clinical histories and biopsies of 17 children with hematuria and vascular C3 deposition on biopsy at Texas Children’s Hospital over an 14-year period. The mean age of presentation was 10.8 (range 4.5–16.6) years with a male preponderance (71%). Family history for hematuria was positive in 6 of 17 patients (35%). Light microscopy was normal or showed only minor abnormalities. Immunofluorescence was negative for IgA and IgG in all patients. Seven patients (41.1%) were noted to have diffuse or focally thin basement membranes on electron microscopy in addition to positive C3 immunofluorescence. The mean follow-up time was 23.8 months, during which 2 of 17 patients (12%) developed worsening proteinuria. The etiopathogenesis of this condition remains unclear, but an underlying immunological process cannot be ruled out. It is possible that this condition represents a stage of an acute glomerulonephritis. Clinical follow-up of these patients is warranted, as the long-term prognosis remains unclear. Received: 30 April 1999 / Revised: 3 December 1999 / Accepted: 7 December 1999     

MPGN II – genetically determined by defective complement regulation?

MPGN II is a rare disease which is characterized by complement containing deposits within the GBM. The disease is characterized by functional impairment of the GBM causing progressive loss of renal function eventually resulting in end stage renal disease.It now becomes evident that in addition to C3NeF, which inhibits the inactivation of the alternative C3 convertase C3bBb, different genetically determined factors are also involved in the pathogenesis of MPGN II. These factors though different from C3NeF also result in defective complement regulation acting either through separate pathways or synergistically with C3NeF. Following the finding of MPGN II in Factor H deficient animals, patients with MPGN II were identified presenting with an activated complement system caused by Factor H deficiency. Factor H gene mutations result in a lack of plasma Factor H or in a functional defect of Factor H protein. Loss of Factor H function can also be caused by inactivating Factor H autoantibodies, C3 mutations preventing interaction between C3 and Factor H, or autoantibodies against C3. Identification of patients with MPGN II caused by defective complement control may allow treatment by replacement of the missing factor via plasma infusion, thus possibly preventing or at least delaying disease progress.     

The interaction of glomerular mesangial cells and epithelial cells

The interaction of cells within the glomerulus plays an important role in the development and progression of glomerular disease. To investigate the interaction of glomerular mesangial cells (GMC) and epithelial cells (GEC), and mediator(s) of this interaction, we investigated the effect of Adriamycin (doxorubicin hydrochloride)-induced (ADR) rat GMC-conditioned medium (GMC-CM) on the incorporation of ³⁵S, ³H-leucine, and ³H-thymidine in normal rat GEC, as well as ³H-thymidine uptake by normal rat GMC in response to ADR-rat GEC-CM. In addition, changes in the responsiveness to interleukin-6 (IL-6) and the products of IL-6 were assessed in ADR-rat GMC. The results showed that: (1) GMC-CM of ADR-rat with heavy proteinuria stimulated GEC proliferation and the synthesis of sulfated compounds and protein, while the GEC-CM of ADR-rat from the same nephrotic period increased GMC proliferation; (2) the ADR-rat GMC had altered responsiveness to IL-6 and its products. The stimulation index results demonstrated the interaction of GMC and GEC in the ADR-induced rat model, and that this interaction related closely to the degree of proteinuria and was mediated by soluble products of the damaged glomerular cell. Received March 29, 1996; received in revised form July 1, 1997; accepted July 2, 1997     

Interferon treatment on glomerulonephritis associated with hepatitis C virus

We report on a 10-year-old girl with glomerulonephritis associated with hepatitis C virus infection, who was treated with interferon-α. On the first renal biopsy at 8 years of age, mild mesangial hypercellularity in a segmental to semiglobal pattern was present in all glomeruli. After 6 months interferon-α therapy, proteinuria diminished completely. However, mesangial proliferation was advanced on the second biopsy at 10 years of age. We concluded that the interferon-α was effective in the treatment of proteinuria despite the lack of pathological improvement. Received: 15 March 2000 / Revised: 11 July 2000 / Accepted: 14 July 2000     

Cutaneous telangiectasias, sparse hair, and type I membranoproliferative glomerulonephritis

 We report the unusual association of normocomplementemic type I membranoproliferative glomerulonephritis in a 10-year-old girl with sparse red hair, absent eyebrows and eyelashes, cutaneous telangiectasias, and an atrial septal defect. Received: 29 December 1997 / Revised: 6 May 1998 / Accepted: 21 May 1998     

C3 nephritic factor and mesangiocapillary glomerulonephritis

The association of a C3 splitting activity, known as C3 nephritic factor (C3NeF), with mesangiocapillary glomerulonephritis (MCGN), especially MCGN type II, has long been known. Several forms of C3NeF are now recognised, the main one being an IgG which acts as an autoantibody binding to factor H, a normally occurring component of the complement system. Complement is in a continuous state of activation with inbuilt checks and controls, and factor H plays a very important part in the controlling mechanisms by preventing the overwhelming activation of complement at the stage of C3 conversion. C3NeF binds to factor H, thus preventing its inhibitory action, and allowing complement activation to proceed with, in vivo, the well-known consequences in MCGN of very low serum levels of C3. The question naturally arose whether C3NeF causes MCGN. Complex relationships between MCGN, C3NeF and partial lipodystrophy, also characterised by C3NeF and hypocomplementaemia, but preceding the development of MCGN, suggest that hypocomplementaemia predisposes to MCGN. Another possibility is that C3NeF acts directly within glomeruli to cause local complement activation and ensuing damage. Neither possibility could be resolved, but some recent observations have restimulated interest in a possible causative role for C3NeF in MCGN. First, factor H deficiency, by mechanisms other than blocking by C3NeF, in animals and man is associated with MCGN. Second, adipocytes, now known themselves to produce complement system proteins, are lysed in vitro by C3NeF, thus suggesting a mechanism for partial lipodystrophy. By analogy, the C3NeF may produce glomerular damage, as glomerular cells produce complement components. Received July 18, 1996; accepted July 24, 1996     

Mesangiocapillary glomerulonephritis associated with meningococcal meningitis,C3 nephritis factor and persistently low complement C3 and C5

We report two unusual cases in which mesangiocapillary glomerulonephritis occurred in association with meningococcal infection. C3 nephritic factor, an autoantibody to alternate pathway C3 convertase, was present. Low serum complement C3 and C5 levels were also noted. The depressed complement levels, in conjuction with terminal complement complexes at the upper limit of normal, suggest activation of the early and late complement cascade. We suggest that children presenting with meningococcal infection should have a regular urine examination, as well as full complement measurements performed, in view of the association with hypocomplementaemic mesangiocapillary glomerulonephritis. Similarly, prophylactic penicillin should be prescribed for patients with mesangiocapillary glomerulonephritis and persistently low C5 levels to prevent meningococcal complications.     

Reference intervals for cystatin C in pre- and full-term infants and children

Cystatin C is a non-glycated, 13-kDa basic protein produced by all nucleated cells. Recent studies have indicated that the plasma concentration of cystatin C is a better marker for glomerular filtration rate (GFR) than plasma creatinine, which is most commonly used for this purpose. We established reference values for plasma cystatin C in pre- or full-term infants and children. For comparison we also measured the creatinine concentration in the same samples. Cystatin C was measured by a commercially available immunoturbidimetric method with a Hitachi 704 analyzer in sera obtained from 58 pre-term infants, 50 full-term infants and 299 older children (132 girls, 167 boys, median age 4.17 years, range 8 days to 16 years). No sex differences were found. The pre-term infants had higher cystatin C concentrations (mean 1.88 mg/l, SD 0.36 mg/l) than the full-term (mean 1.70 mg/l, SD 0.26 mg/l, P=0.0145). The reference interval for pre-term infants calculated non-parametrically was 1.34–2.57 mg/l and for full-term infants 1.36–2.23 mg/l. The cystatin C concentration decreased rapidly after birth, and above 3 years of age did not depend on age. The reference interval for children 3–16 years of age calculated non-parametrically was 0.51–1.31 mg/l. Younger children (<1 year: 0.75–1.87 mg/l; 1–3 years: 0.68 –1.60 mg/l) had slightly, but significantly, higher plasma cystatin C levels. Received: 26 January 2000 / Revised: 12 April 2000 / Accepted: 17 April 2000     

Binding of monofluorophosphate to α2-macroglobulin and C3

After administering an oral dose of monofluorophosphate (MFP) to human beings or rats, a fraction of the drug appears in plasma that is bound to proteins, establishing a previously undetected compartment of nondiffusible fluoride. This article documents experiments performed in vitro, describing the binding of MFP to two plasma globulins: α₂-macroglobulin and C3 (a β-globulin). MFP binds irreversibly to these proteins through a stable bond. MFP binds to purified α₂-macroglobulin or to C3 with a molar ratio MFP: protein close to unity. MFP binding reduces significantly the biological activity of these proteins, which share in common a macrocyclic 4-residue ring thiolactone (Cys—Gly—Glu—Glu). The binding site of MFP is as yet unknown. Protein-bound MFP appeared in the plasma of volunteers during the 5–7 hours following intake. Peak concentration of protein-bound MFP and maximal reduction of α₂-macroglobulin activity was observed 2 hours after intake. Clearance of protein-bound MFP coincided with the return of α₂-macroglobulin to basal levels. Received: 1 September 1995 / Accepted: 8 May 1996     

C3肾小球肾炎的诊断和中西医结合治疗

C3肾小球肾炎(C3GN)是指免疫荧光仅见C3沉积而免疫球蛋白和C1q阴性,电镜下见内皮下和(或)系膜区电子致密物沉积的一种肾小球病。随着病理学、免疫学的逐步发展,我们对C3GN的认识不断提高。目前临床医生主要通过临床表现、实验室检查(补体成分异常)及病理三方面来对C3GN进行诊断。C3GN作为一种最近提出的疾病,现有资料有限,在诊断上需要慎重鉴别。C3GN尚无特效的治疗方法,作用于C5的人造单克隆抗体依库丽单抗、补体调节剂CR1以及以雷公藤甲苷为代表的中西医结合对症治疗有望获得良好的疗效。本病预后呈多样性,在对症支持的基础上,中西医结合治疗通过免疫抑制等机制有望控制疾病的进展,而更加有效的药物亟待研发。     

Bone Response to In Vivo Mechanical Loading in C3H/HeJ Mice

Bone, being sensitive to mechanical stimulus, adapts to mechanical loads in response to bending or deformation. Although the signal/receptor mechanism for bone adaptation to deformation is still under investigation, the mechanical signal is related to the amount of bone deformation or strain. Adaptation to changes in physical activity depends on both the magnitude of increase in strain above average daily levels for maintaining current bone density and the Minimum Effective Strain (MES) for initiating adaptive bone formation. Given the variation of peak bone density that exists in any human population, it is likely that variation in levels for MES is, to a considerable degree, inherited and varies among animal species and breeds. This study showed a dose-related periosteal response to loading in C3H/HeJ mice. The extent of active formation surface, the rate of periosteal bone formation, and area of bone formation increased with increasing peak periosteal strain. In these mice, the loaded tibia consistently showed lower endocortical formation surface and mineral apposition rate than the nonloaded bones at every load level. Although periosteal expansion is the most efficient means of increasing moment of inertia in adaptation to bending, a dose response increase in endocortical formation would have been predicted. Our characterization of the mouse bone formation response to increasing bending loads will be useful in the design of experiments to study the tibial adaptive response to known loads in different mouse breeds. Received: 17 February 1998 / Accepted: 9 December 1998     

Acute non-proliferative glomerulitis: a cause of renal failure unique to children

Over a 31-year period, we have encountered 13 children with a disease entity not reported by other clinics that leads to rapidly progressive crescentic glomerulonephritis. Gross hematuria, rapidly declining renal function, and a serum C3 level at the lower limit of normal or slightly depressed usually characterized the disease onset; hypertension and nephrotic syndrome were absent. Glomerular IgG was absent, but large C3-containing subepithelial deposits on the paramesangial basement membrane (GBM) were always present. Because of these deposits and because dense alteration of the GBM was found in 3 patients, the disease may resemble membranoproliferative glomerulonephritis type II, but is distinguishable on other morphological and clinical grounds. The absence of anti-neutrophil cytoplasmic antibody, tested for in 5 of 13 patients, is one of several ways the disease differs from the pauci-immune glomerulonephritis of adults. Clinically and by glomerular morphology, it also differs from severe poststreptococcal acute glomerulonephritis. Treatment with high-dose corticosteroids has been highly successful. Because in this series the disease occurred only in children under age 12 years and the amount of silver-positive mesangial matrix was normal, indicating absence of mesangial proliferation, it has been designated juvenile acute non-proliferative glomerulitis. Received: 31 March 1999 / Revised: 15 October 1999 / Accepted: 20 October 1999     

Correlation between serum C3 and glomerular microthrombosis in patients with lupus nephritis

Objective To investigate the correlation between serum C3 and glomerular microthrombosis in patients with lupus nephritis (LN). Methods Patients who were diagnosed as LN by renal biopsy hospitalized in Department of Nephrology, the First Affiliated Hospital of Shenzhen University from January 2010 to February 2019 were retrospectively analyzed and they were divided into glomerular microthrombosis group (GMT group) and non-glomerular microthrombosis group (non-GMT group). The demographic data, clinical characteristics, pathology and prognosis of the two groups were compared. Logistic regression and smooth curve fitting of generalized additive mixed model analysis were used to explore the correlation between serum C3 and glomerular microthrombosis. Renal prognosis of the two groups were compared by the Kaplan-Meier survival curve. Results A total of 116 patients were enrolled, aged (32.79±11.43) years old, in which 108 cases (93.10%) were female. Thirty-seven patients (31.90%) were confirmed to be combined with GMT (GMT group) and 79 cases were not (non-GMT group). Compared with the non-GMT group, patients in the GMT group were relatively older (t=-2.876, P=0.002), with higher proportion of hypertension ( χ2=7.492, P=0.006)，higher urine protein quantitation (Z=-2.115, P=0.003), lower levels of eGFR and serum complement C3 (Z=3.469, P＜0.001; t=1.744, P＜0.001), higher systemic lupus erythematosus disease activity index (t=-2.758, P=0.007). As to the pathological characteristics, type IV LN patients were the majority (72.97%). Proportion of crescents and pathological activity indicators of the GMT group were higher (Z=-1.866, P=0.002; t=-5.005, P＜0.001), nuclear fragmentation, endothelial hyperplasia and renal tubular atrophy were more serious ( χ2=14.987, P＜0.001; χ2=15.695, P＜0.001; χ2=4.130, P=0.042). Multivariate logistic regression analysis indicated that serum complement C3 was a relational factor of the formation of GMT in LN patients (OR=0.966, 95％CI 0.938-0.995, P=0.023). Smooth curve fitting of generalized additive mixed model analysis indicated that level of complement C3 had a linear relationship with the changing trend of GMT. The Kaplan-Meier curve showed that there were statistical differences between the two groups in terms of complete remission of urine protein (Log-rank χ2=5.858, P=0.016) and doubled serum creatinine /end-stage renal disease (Log-rank χ2=3.945, P=0.047). Conclusions Serum C3 is closely related to the formation of GMT in LN patients, and statistical differences were demonstrated in the renal prognosis of GMT group and non-GMT group.