C3D deposition in peritubular capillaries indicates a variant of acute renal allograft rejection characterized by a worse clinical outcome

BACKGROUND: C4d deposition in peritubular capillaries (PTCs) is a sign of humoral renal allograft rejection and an independent predictor of graft survival. Few investigators have focused on the meaning of capillary C3 deposition in rejecting grafts. Because C3 production can result from both classic and alternative pathway activation of the complement cascade, it is not clear whether C3 deposition indicates a distinct entity of acute rejection (AR) or merely represents a separate form of C4d-positive AR. METHODS: We examined the deposition of C3d in the PTCs of recipients with AR in the first year posttransplantation (n=30). Clinical outcome variables and histology were compared with C3d-negative control patients (n=82). RESULTS: C3d-positive patients demonstrated more frequent preexisting T-cell antibodies (57%) and more re-transplants (37%), and they received more blood transfusions (mean 10.3 units). C3d-positive patients experienced more frequent multiple AR episodes (57%) and delayed graft function (36.7%). All nine C3d-positive recipients screened for posttransplantation donor-specific human leukocyte antigen antibodies demonstrated positive results. Graft failure occurred in 23% of C3d-positive recipients (7.3% in the control group) (P=0.03). C3d-positive biopsies showed significantly less tubulitis (P=0.03), whereas congestive PTCs with intraluminal accumulation of polymorphonuclear leukocytes were conspicuous. Thrombi, fibrinoid necrosis, and acute tubular necrosis were not more pronounced. In 19% of rejection biopsies, C3d deposition in PTCs was present without C4d deposition. In the remaining biopsies, C3d and C4d deposition was found simultaneously. CONCLUSIONS: The deposition of complement factor C3d in PTCs indicates a variant type of AR characterized by a worse clinical outcome.     

Afferent arteriolar C3 disease--a distinct pathological entity

Afferent arteriolar C3 deposition was the sole histological abnormality in 79 and the major histological abnormality in an additional 39 of 959 renal biopsies performed over a 10-year period. Of these 79 patients, hematuria was the presenting symptom in 90%, with coincident loin pain in 49%. Urine microscopy of asymptomatic first-degree relatives revealed hematuria in 44% of children and siblings and 54% of parents, suggesting autosomal dominant inheritance. Arteriolar C3 deposition was confirmed by biopsy in four asymptomatic relatives with hematuria. Generalized thinning of glomerular basement membrane (less than 200 nm) was observed in five patients and focal thinning was observed in six patients with coincident afferent arteriolar C3 deposition. Seven other patients were identified as having generalized thinning of glomerular basement membrane in the absence of afferent arteriolar C3 deposition. Renal function was stable and similar in all groups studied over 37.9 +/- 23.7 months. No difference in clinical presentation or urinary abnormalities was evident between the groups. No arteriolar C3 deposition was evident in eight autopsy specimens with no known renal disease. It was concluded that afferent arteriolar C3 deposition is a marker of a distinct hereditary pathological entity, with differentiation from thin basement membrane disease not possible on clinical grounds. The medium- and long-term prognoses with respect to renal function are excellent.     

Evolution of immunoglobulin deposition in C3-dominant membranoproliferative glomerulopathy

Background

Complement 3 glomerulopathy (C3GN) is a newly proposed subcategory of glomerular disease with features including membranoproliferative glomerulonephritis (MPGN), C3-dominant immunofluorescent staining without appreciable immunoglobulin deposition, and electron-dense deposits. Aberrations of alternative complement pathway (AP) have been found in many C3GN patients.

Case-diagnosis/treatment

A 13-year-old boy presented with edema in association with an upper respiratory infection. Studies demonstrated nephrotic syndrome with hematuria and markedly low C3 and C4. Initial renal biopsy showed MPGN with strong C3 and immunoglobulin deposition. The patient partially responded to immunosuppression. Follow-up biopsies at 10 months and 3 years demonstrated MPGN with strong C3, with little to no immunoglobulin deposition. Based on this and elevated SC5b-9, treatment was changed to eculizumab with further decrease in proteinuria.

Conclusions

Serial biopsies illustrated marked variability in immunoglobulin deposition in MPGN with persistently strong C3 deposition. Whether this evolution was related to the course of disease or to therapeutic intervention, the pathologic progression documented in this series of biopsies challenges the newly proposed subcategories of MPGN.     

Mesangial deposition of IgA2 subclass and lectin pathway-mediated complement activation in IgA glomerulonephritis

Three pathways are recognized in the complement activation cascade. The aim of our study was to elucidate immunohistologically which complement pathway is associated with the activation in IgA glomerulonephritis (GN) and the relation of IgA subclass to the complement activation. Immunohistological staining was performed on biopsied renal specimens from 36 patients with IgA GN, 10 with systemic lupus erythematosus (SLE) and 16 with other glomerulonephritides using polyclonal antibodies of IgG, IgA, IgM, C3c, C4, C1q and monoclonal antibodies of IgA1, IgA2, mannose-binding lectin (MBL) and MBL-associated serine protease-1 (MASP-1). Mesangial deposits of IgA1, IgA2, C3c, C4, MBL and MASP-1 were detected in 19 of the 36 patients with IgA GN, and IgA2 and MBL/MASP-1 were colocalized in the mesangium in these 19 patients. The remaining 17 patients showed mesangial deposition of IgA1 alone. Twelve of these 17 patients presented mesangial deposition of C3c without deposition of C4, MBL and MASP-1. No deposition of C1q was evident in IgA GN patients. Three of the 10 SLE patients showed glomerular deposition of MBL and MASP-1 without deposition of IgA2. No patient with other glomerulonephritides showed glomerular deposition of IgA1, IgA2, MBL and MASP-1. There was no correlation in clinical and pathological indicators between IgA2-positive and IgA2-negative patients with IgA GN. In conclusion, alternative pathway-mediated complement activation is associated in patients with mesangial deposition of IgA1 alone in IgA GN. In those with the deposition of both IgA1 and IgA2, both alternative and lectin pathways are activated, and mesangial deposition of IgA2 is associated with the lectin pathway-mediated complement activation in IgA GN.     

Incidence of latent mesangial IgA deposition in renal allograft donors in Japan

BACKGROUND: Mesangial immunoglobulin A (IgA) deposition is incidentally encountered in asymptomatic individuals, but its precise frequency and significance had not been clarified. The background of the latent IgA deposition is related to the epidemiology and pathogenesis of IgA nephropathy. METHODS: Zero-hour allograft biopsies were performed in 510 renal transplantations (446 living donors, and 64 cadaveric donors) at the Kidney Center of Tokyo Women's Medical University. Mesangial IgA and C3 deposition were analyzed immunohistochemically, and the frequency and clinicopathologic features of mesangial IgA deposition were investigated. RESULTS: Mesangial IgA deposition was present in 82 (16.1%) of the total 510 allografts with no statistical difference between living donors (72/446, 16.1%) and cadaveric donors (10/64, 15.6%) or between blood-related donors (66/392, 16.8%) and nonblood-related donors (16/110, 14.5%). Mesangial C3 deposition was present in 16 (19.5%) of the 82 allografts with mesangial IgA deposition. The grade of hematuria in IgA(+) donors was significantly higher than IgA(-) donors (1.30 +/- 1.17 vs. 0.86 +/- 0.89, P = 0.025). Histologic investigation of IgA(+) allografts revealed the frequency of mesangioproliferative glomerulonephritis (PGN) was significantly higher in IgA(+)/C3(+) allografts (8/16, 50%) than in IgA(+)/C3(-) allografts (11/66, 16.7%) (P = 0.0084). Moreover, the number of infiltrated macrophages to glomerulus (cells/glomerular cross section) was significantly higher in the IgA(+)/C3(+) allografts than in IgA(+)/C3(-), IgA(-)/C3(+) and IgA(-)/C3(-) allografts (1.10 +/- 0.62 vs. 0.61 +/- 0.42, P = 0.0008; 0.47 +/- 0.34, P = 0.023; and 0.37 +/- 0.23, P = 0.002, respectively). CONCLUSION: The latent mesangial IgA deposition was a relatively common phenomenon in the healthy Japanese donors. This phenomenon was associated with mild degree of microhematuria, mesangial proliferation and glomerular macrophage infiltration in some of the affected individuals, especially with combined IgA and C3 deposition.     

Complement deposition in early cardiac transplant biopsies is associated with ischemic injury and subsequent rejection episodes.

BACKGROUND: Prolonged warm or cold ischemia is associated with poor survival of cardiac transplants, and ischemic changes in early posttransplantation endomyocardial biopsies correlate with the later development of chronic rejection. In animal models, tissue ischemia has been shown to activate complement. METHODS: To determine whether ischemic changes in endomyocardial biopsies were associated with complement deposition, biopsies obtained 1-3 weeks after transplantation from 33 patients were evaluated immunohistologically for C4d and C3d deposition as well as for IgM, IgG, and IgA. The histological changes associated with ischemic injury were scored independently, using previously reported criteria without knowledge of the immunohistochemical results. RESULTS: Diffuse capillary and pericapillary deposition of C4d or C3d were detected in endomyocardial biopsies of 14 of the 33 patients. The majority of biopsies (79%) with C4d or C3d deposits had histological evidence of ischemic injury, including eight of the nine biopsies containing both C4d and C3d deposition. In contrast, only 8 of 18 (45%) of the biopsies without C4d or C3d deposition had ischemic injury. Only trace amounts of IgM and no IgG or IgA were demonstrable in the biopsies. Only 2 of the 14 biopsies with C4d or C3d deposition had evidence of moderate acute rejection, whereas 5 of the 18 biopsies without C4d or C3d deposition had moderate acute rejection. However, C4d and C3d deposition did correlate with repeated acute rejection episodes on subsequent biopsies. CONCLUSIONS: Thus, ischemic changes are associated with the activation of complement. Complement activation may in turn promote tissue injury and provide a potential target for future treatment.     

Participation of complement components in glomerular deposition in IgA nephropathy

To clarify the role of complement components in glomerular deposition in IgA nephropathy, clinicopathological and immunohistological studies were performed on 299 patients (171 males and 128 females; age, 9-71 years). Glomerular IgA deposition with IgG and/or IgM was observed more frequently in patients with Clq and/or C4 than in those with only C3 deposition (P less than 0.001). Patients with glomerular deposition of Clq and/or C4 showed more severe proteinuria (1 g/24 hr less than), a lower glomerular filtration rate (GFR), a higher incidence of duplication of capillary walls and more severe proliferation of mesangial cells and an increase in mesangial matrix (P less than 0.05), as compared to those without both Clq and C4. Patients with glomerular C3 deposition had significantly lower serum CH50 levels at the time of renal biopsy (P less than 0.02) and a significantly higher incidence of sclerotic lesions (P less than 0.05). Patients with C3 deposition in the mesangium and peripheral capillaries had significantly higher serum IgA levels (P less than 0.02), a significantly higher incidence of adhesion (P less than 0.01), duplication and endocapillary proliferation (P less than 0.05) and a more severe increase in mesangial cells (P less than 0.01) than those with C3 deposition only in the mesangium. The above findings demonstrate that analysis of the complement system in glomeruli is important for the evaluation of glomerular damage, clinical findings and prognosis.     

Human leukocyte antigen antibodies and human complement activation: role of IgG subclass, specificity, and cytotoxic potential

BACKGROUND: Human leukocyte antigen (HLA) antibodies are defined as complement (C) fixing and clinically relevant based upon the complement-dependent cytotoxicity (CDC) test. However, the sub-lytic activation of individual C components is of critical biologic significance. The requirements of HLA antibodies to activate human C are not known. METHODS: IgG, IgM, IgG subclasses, and human C3b deposition upon T cells were evaluated by flow cytometry with sera from HLA-sensitized patients and human monoclonal HLA antibodies. RESULTS: Comparative studies showed that there was poor correlation between the amount of IgG on target cells and their ability to produce CDC. Human C3b deposition was influenced more by the particular serum/cell combination under study than by the amount of IgG, with some combinations showing high IgG and low C3b and others showing low IgG and high C3b. IgG1 was the predominant IgG subclass in all patients. The other subclasses were low or undetectable and did not correlate with C3b deposition. Human monoclonal HLA antibodies, mostly IgG1, did not activate human C efficiently despite high IgG binding. However, combinations of two monoclonal antibodies to different epitopes of the same antigen did produce significant C3b deposition. CONCLUSIONS: Contrary to common assumptions, CDC, IgG binding, and IgG subclass are poor predictors of human C activation by HLA antibodies. The mix of specificities in a given serum and the antigens of a particular target cell appear to determine the efficiency of C activation. Measuring both antibody and C3b deposition (or other C component) may improve the assessment of donor-recipient compatibility.     

Complement activation in early protocol kidney graft biopsies after living-donor transplantation

BACKGROUND: To gain insight into complement activation in kidney grafts, we studied the deposition of components from all complement pathways in protocol biopsies from living-donor recipients that were taken 1 week (median 7 days) after transplantation. METHODS: Graft protocol biopsies (n=37) were taken consecutively and stained for two-color immunofluorescence, with antibodies to C4d, C3, C1q, factor B, C6, terminal C5b-9 complement complex, mannose-binding lectin (MBL), and MBL-associated serine protease-1, combined with an endothelial marker. Light and electron microscopy were performed in all cases. Clinical acute rejection (AR), graft loss, and long-term kidney function were recorded. Baseline biopsies from 15 of the patients served as controls. RESULTS: Endothelial C4d deposition was demonstrated in peritubular capillaries in 11 of 37 cases (30%), of which 9 of 11 (82%) experienced clinical AR but only 6 of 11 (55%) experienced AR as defined by histopathologic criteria. Biopsies from three patients, two with early graft loss, showed diffuse global C4d in the glomerular endothelium with codeposition of C3 in all patients and MBL-associated serine protease-1 in one patient. Focal peritubular capillary C3 deposition was found in two additional C4d-positive cases with AR. No posttransplant deposition was demonstrated for the other components. CONCLUSIONS: Early diffuse C4d deposition in the kidney graft capillaries is closely related to acute humoral rejection, whereas focal staining may occur with mild AR or, rarely, without rejection. Codeposition of C3 indicates early AR with a higher risk of graft loss. In most cases, activation was limited to C4d, indicating efficient in situ regulation of complement activation.     

The effect of pH and nucleophiles on complement activation by human proximal tubular epithelial cells.

BACKGROUND: Activation of urinary complement proteins in situ by proximal tubular epithelial cells (PTEC) may contribute to the mediation of tubulointerstitial injury in patients with significant proteinuria. However, the mechanism involved is unclear, and the role of changes in urinary pH and in the concentrations of urea or ammonia requires further clarification. METHODS: The protein fraction of urine samples from nine patients with proteinuria >1.5 g/day was purified. A cell ELISA involving cultured HK-2 PTEC was used to investigate the capacity of urinary protein to promote the deposition of both C3 and C9 on the cell surface. The effect of variations in pH (5.5-8.0) and in the concentration of urea and ammonia was also examined. C3 was purified and used to further investigate the mechanism of complement deposition. RESULTS: Urine samples from the majority of patients induced deposition of C3 and C9 on the surface of HK-2 cells via the alternative pathway. This process was maximal at acidic pH values. Preincubation of urinary complement or serum with urea or ammonia inhibited C3 deposition. Purified C3 incubated with HK-2 cells showed no evidence of activation in the absence of other complement components. CONCLUSIONS: These data suggest that bicarbonate protects against complement-mediated damage in the lumen by increasing the local pH, rather than by inhibiting the generation of ammonia. PTEC appear to activate complement through provision of a 'protected site' on their surface, rather than by the activation of C3 by convertase-like protease(s).     

Role of CXCR3 in cellular but not humoral renal allograft rejection

CXCR3, a chemokine receptor mainly expressed by T cells, is involved in animal transplant models and in human allograft rejection. CXCR3 expression was localized in formalin-fixed, paraffin-embedded renal allograft biopsies without signs of rejection (C4d-negative, Banff 0, n = 16), with C4d deposits as a sign of humoral rejection (C4d-positive, Banff 0, n = 8), with cellular rejection (C4d-negative, Banff I, n = 7) and with signs of both cellular and humoral rejection (C4d-positive, Banff 1, n = 5). Small, round infiltrating cells were CXCR3-positive. A high number of these cells was present in biopsies with cellular rejection (independent of C4d deposition). CXCR3-positive cells diffusely infiltrated the interstitium, including the tubular epithelium (tubulitis). CXCR3 scores and the area of CXCR3 staining were significantly higher in cellular rejection, when compared to biopsies without rejection, and with deposition of C4d alone. CXCR3-positive cells infiltrate renal allografts during cellular rejection, whereas C4d deposition is not associated with the recruitment of these cells.     

Clinico-pathological characterization and outcome of primary focal segmental glomerular sclerosis with deposition of IgM

Objective To explore the clinico-pathological features and outcomes of primary focal segmental glomerular sclerosis with IgM deposition. Methods One hundred and two patients with primary focal segmental glomerular sclerosis (pFSGS) in Hangzhou hospital of traditional Chinese medicine between 1996 and 2012 were retrospectively studied. The patients were divided into IgM deposition group (n=66) with IgM deposition in glomeruli and none-IgM deposition group (n=36)without IgM deposition. Baseline and clinical characteristics of all FSGS patients were assessed and outcomes were reviewed. The survival rates of the patients were analyzed using theKaplan-Meiermethod. Results (1) There were not difference in age, sex ratio, incidence of microscopic hematuria, hypertension, renal insufficiency, eGFR, Ccr and Scr between two groups. However, proteinuria, incidence of nephrotic syndrome, urine microalbumin, urine NAG, serum cholesterol, serum high-density lipoprotein, and serum IgM in IgM deposition group were significantly higher than those in none-IgM deposition group (P＜0.05), serum albumin and serum IgA in IgM deposition group were significantly lower than those in none-IgM deposition group (P＜0.05). (2) The IgM deposition group had a significantly higher incidence of glomerular deposition of IgA, IgG, C3, C1q and fibrinogen than none-IgM deposition group (P＜0.05). The score of mesangial matrix proliferation in the IgM deposition group was lower than that in none-IgM deposition group (P＜0.05). (3) fifty-four patients (35 patients in IgM deposition group and 19 patients in none-IgM deposition group） were followed-up for a median of 64.6 (22.8, 103.8) months. Progression to renal failure was observed in 5 patients of IgM deposition group and none in none-IgM deposition group. Compared with the none-IgM deposition, the survival rates in the IgM deposition group were statistically lower (P＜0.05).Conclusions PFSGS patients with IgM deposition were severer in proteinuria, higher incidence ofIgA, IgG, C3, C1q and fibrinogen deposition in glomeruli and worse outcome than those without IgM deposition.     

Clearance of complement by human vascular endothelial cells: effects of hypoxia/reoxygenation and IL-1β activation

Antibody-mediated rejection is characterized by deposits of complement (C) C4 and C3 split products on endothelial cells (ECs). C3 split products are critical mechanistically and diagnostically because they are deposited in amplified quantities, bind covalently to ECs and act as ligands for leukocytes. This study was designed to determine whether cultured vascular human ECs could clear covalently bound C3 split products from their surface. An immunoglobulin M (IgM) antibody against beta(2)-microglobulin of major histocompatibility complex class I antigens was used to activate C in human serum. Some cells were exposed to hypoxia/reoxygenation and/or interleukin 1beta (IL-1beta) prior to incubation with antibody. C3b/iC3b and C3d deposition on the cell surface was measured by flow cytometry. Incubation with antibody followed by human serum caused a dose-dependent deposition of C3b/iC3b and C3d. Over half of deposited C3b/iC3b and one-third of C3d were cleared from the cell surface during a 3-7-h incubation period with human serum. Neither hypoxia/reoxygenation nor IL-1beta further increased the deposition of C3b/iC3b and C3d, and only slightly modulated their rates of clearance. In summary, human ECs rapidly clear iC3b and C3d from their surface. This finding may have important diagnostic and mechanistic implications to transplantation because C3d is used as a marker of antibody-mediated rejection.     

Subclinical C1q Nephropathy Combined with Possible Donor-Derived IgA Deposition in a 1-Year Kidney Allograft Biopsy: A Case Report

Few previous studies have reported immune-complex nephropathy that has not been classified as a specific phenotype in kidney allografts. We report a case of a de novo subclinical “full-house” pattern of deposition in a pediatric transplantation recipient with possible donor-derived IgA deposition. A five-year-old boy underwent living kidney transplantation due to congenital kidney and urinary tract anomalies. A one-hour implantation biopsy revealed IgA deposition. A four-month protocol biopsy finding showed less intense IgA deposition, in contrast with the one-hour biopsy, and trace para-mesangial deposits. A one-year protocol biopsy demonstrated a full-house deposition pattern and massive electron-dense deposits with minor glomerular changes. At the time of the one-year biopsy, kidney function was stable, with no urinalysis abnormalities. No evidence of systemic lupus erythematosus was observed in clinical and serologic examinations. Mesangial IgG, IgM, C3, and C1q deposition was codominant, and IgA deposition was weaker. We diagnosed this case as C1q nephropathy combined with remaining donor-derived IgA deposition. Few studies have reported C1q nephropathy in kidney allograft; further accumulation of cases is required. To distinguish between donor-derived and de novo glomerular lesions, it is important to assess the serial histologic findings of immunofluorescence and electron microscopy. Here, we report a rare case of subclinical C1q nephropathy with possible donor-derived IgA nephropathy.     

New knowledge on the calcium pyrophosphate dihydrate (CPPD) crystal deposition disease in the cervical ligamentum flavum

A case of 64-year-old Japanese woman with cervical radiculomyelopathy caused by the deposition of both calcium pyrophosphate dihydrate (CPPD) and hydroxyapatite crystals in the cervical ligamentum flavum is reported. The patient developed paresthesia in her both hands and gait disturbance in the previous six months. Neurological examination revealed generalized hyperreflexia and hypesthesia in the C7 region. Neuroradiologically, two nodular opacifications were shown in the C3-4 and C5-6 level. CT scan revealed linear and symmetrical calcifications in the C3-4 and nodular calcifications in the C5-6 level. En bloc laminectomy was performed and the patient was discharged from the hospital with improvements of neurological symptoms. Specimens of the spinal laminae and ligamenta flava were studied by light microscopy, scanning electron microscopy (SEM), energy dispersive X-ray microanalysis (X-MA) on SEM, and an X-ray diffraction study was carried out on the crystals. The results showed A. CPPD crystal depositions throughout the ligamenta flava together with a minimal thickening of the ligaments. The deposition was seen in the midzone of the ligaments forming a plate-like distribution and forming lines in the cut surface, the latter coincided well with the CT finding at the C3-4 level. B. The nodule (7 X 6 X 6 mm in size) at the C5-6 level was composed of two crystals, CPPD and hydroxyapatite, the latter being encased by the former. The thickness of the CPPD layer was quite thin varying from 10 to 100 mu. Myelographically, the spinal cord was most severely compressed by the C5-6 nodule. C. Because of the absence of family histories and predisposing factors, the case was considered one of primary or idiopathic CPPD crystal deposition disease. The origin of the deposition of mixed crystals was discussed and it appeared likely that the central part of CPPD crystal deposition had transformed to hydroxyapatite at the C5-6 level. In the literature a considerable number of cases have been reported under the title, "Calcification of the Ligamentum Flavum", and some of them have been shown to have hydroxyapatite deposition. Considering the great similarities in clinical, radiological and histological findings between the so-called "calcification of the lig. fl." and CPPD crystal deposition disease, the present case was the first to clearly indicate that these two conditions belong to a single category, i.e. CPPD crystal deposition disease.(ABSTRACT TRUNCATED AT 400 WORDS)     

Efficacy of Targeted Complement Inhibition in Experimental C3 Glomerulopathy

C3 glomerulopathy refers to renal disorders characterized by abnormal accumulation of C3 within the kidney, commonly along the glomerular basement membrane (GBM). C3 glomerulopathy is associated with complement alternative pathway dysregulation, which includes functional defects in complement regulator factor H (FH). There is no effective treatment for C3 glomerulopathy. We investigated the efficacy of a recombinant mouse protein composed of domains from complement receptor 2 (CR2) and FH (CR2-FH) in two models of C3 glomerulopathy with either preexisting or triggered C3 deposition along the GBM. FH-deficient mice spontaneously develop renal pathology associated with abnormal C3 accumulation along the GBM and secondary plasma C3 deficiency. CR2-FH partially restored plasma C3 levels in FH-deficient mice 2 hours after intravenous injection. CR2-FH specifically targeted glomerular C3 deposits, reduced the linear C3 reactivity assessed with anti-C3 and anti-C3b/iC3b/C3c antibodies, and prevented further spontaneous accumulation of C3 fragments along the GBM. Reduction in glomerular C3d and C9/C5b-9 reactivity was observed after daily administration of CR2-FH for 1 week. In a second mouse model with combined deficiency of FH and complement factor I, CR2-FH prevented de novo C3 deposition along the GBM. These data show that CR2-FH protects the GBM from both spontaneous and triggered C3 deposition in vivo and indicate that this approach should be tested in C3 glomerulopathy.     

Mesangial C3 deposition and decreased serum C3levels in patients with IgA nephropathy

Objective To explore theclinical significance of complementactivation in IgA nephropathy (IgAN) patients and provide new potential therapy targets. Methods Biopsy-proven IgAN patients admitted in our renal center were retrospectively recruited. Demographic, baseline clinical and pathological data were recorded as well as the follow-up results. Patients were divided into three groups, negative, weak positive and strong positive group, according to the intensity of C3 deposition in mesangial area of glomurili. Decreased serum C3 level was defined as C3＜85 mg/dl. Results In this study, 528 IgAN patients were recruited and meanfollow-up time was3 years. There were 119 (22.5%), 164(31.1%), 245(46.4%) patients in the negative, weak positive and strong positive group respectively; 93(21.7%) patients had decreased serum C3 level and 335(78.3%) patients had normal serum C3 level; Significant negative correlation was found between mesangial area of C3 deposition and serum level of C3(r＝-0.209, P＜0.01). Theage or sex were similar among different groups of mesangial C3 deposition. In univariate analysis, higher baselineserum creatinine,uric acid and IgAlevels, and lower estimated glomerular filtration rate(eGFR), body mass index (BMI) levels were associated with a higher grade of mesangial C3 deposition (P＜0.05). Endocapillary hypercellularity and tubular atrophy or interstitial fibrosis were more prominent in patients with higher grade mesangial deposition of C3. Compared with the patients with normal serum C3 level, patients with decreased serum C3 level had lowerwhite blood cells,hemoglobin,triglyceride, cholesterol, eGFR level and higher serum creatinine level(P＜0.05). During the follow-up,a total of 54 patients developed to end stage renal disease (ESRD), the incidence of ESRD was 23.7% in patients with decreased serum C3 level and 8.4% with normal C3 level.Kaplan-Meieranalysis showed that median outcome-free survival timeof patients with decreased serum C3 levelwas significantshorter than patients with normal serum C3 level [(145.0±22.5) months vs (150.8±17.0) months, P＜0.01]. Cox regression proportional hazards models showed that after adjusting by sex, ageand clinical indicators (MAP, eGFR, serum albumin, urine protein and hemoglobin level), decreased serum C3level (HR＝0.97, 95%CI 0.96, 0.99, P＜0.01) remained be an independent riskfactor of ESRD. Conclusions There are different levels of complement activation in patients with IgAN. Complement activation is associated with baseline renal function and clinical outcomes, and decreased serum C3level is an independent riskfactor of ESRD in IgAN patients. Complement activation may be involved in the progression of IgAN.     

Inhibition of complement factor C5 protects against renal ischemia-reperfusion injury: inhibition of late apoptosis and inflammation

BACKGROUND: Complement has been implicated in the pathophysiology of renal ischemia-reperfusion (I/R) injury. However, the mechanism underlying complement-mediated renal I/R injury is thus far unknown. To investigate the involvement of complement in I/R injury, we studied the activation and deposition of complement in a murine model of renal I/R injury. Furthermore, we examined the effect of inhibition of complement-factor C5 on renal I/R injury. METHODS: Mice were subjected to 45 min of unilateral ischemia and subsequent contralateral nephrectomy and reperfusion for 2, 12, or 24 hr. Mice were control treated or treated with BB5.1, a monoclonal antibody that prevents cleavage of complement factor C5, thereby preventing C5a generation and formation of the membrane attack complex (MAC). RESULTS: Renal I/R induced extensive deposition of C3 early after reperfusion, whereas C6 and C9 deposition (MAC formation) occurred relatively late. I/R-induced complement deposition was mainly localized to tubular epithelium. Treatment with BB5.1 totally prevented MAC formation but also reduced C3 deposition. Inhibition of C5 strongly inhibited late inflammation, as measured by neutrophil influx and induction of the murine CXC chemokines macrophage inflammatory protein-2, KC, and lipopolysaccharide-induced CXC chemokine. Anti-C5 treatment furthermore abrogated late I/R-induced apoptosis, whereas early apoptosis was not affected. Moreover, BB5.1 treatment significantly protected against I/R-induced renal dysfunction. CONCLUSIONS: Renal I/R is followed by activation of the complement system and intrarenal deposition of C3 and MAC. Complement activation plays a crucial role in the regulation of inflammation and late apoptosis. Complement inhibition, by preventing C5 activation, abrogates late apoptosis and inflammation, being strongly protective against renal function loss.     

Intraprostatic antibody deposition in chronic abacterial prostatitis

Sixty patients with chronic abacterial prostatitis and 21 men without prostatitis were studied. Transperineal prostatic biopsies taken under transrectal ultrasound control were examined for antibody, complement (C3) and fibrinogen deposition using a direct immunofluorescence (IF) technique; 34 patients (57%) had prostatic tissue that displayed IF staining compared with only 1 (5%) in the non-prostatitis group. IF staining for IgM was found in 85%, for C3 in 44%, for IgA in 35% and for fibrinogen in 24%, but the IgG subclass was not detected. Antibody deposition was mainly periglandular and glandular and in the wall of vessels. Five symptoms, particularly poor urinary flow, irritative voiding and urgency, were significantly correlated with IgM and C3 deposition and, to a lesser extent, fibrinogen deposition. The aetiology of chronic abacterial prostatitis remains obscure but several possible mechanisms are discussed. The link between symptomatology and immunology could rest with functional outflow obstruction causing intraprostatic reflux of urine, this in turn inciting an immunological response, the inducing antigens being organism remnants or products, urinary constituents or autoantibodies.     

C5b-9 and adhesion molecules in human idiopathic membranous nephropathy.

BACKGROUND: Cellular immune responses and C5b-9 seem to play an important role in the pathogenesis and progression of idiopathic membranous nephropathy (IMN). The aim of the study was to investigate the role of C5b-9 and adhesion molecules in the pathogenesis of the disease. METHODS: The clinical and pathological data of 35 patients with biopsy-proven IMN were correlated with immunohistochemical findings using monoclonal antibodies against T lymphocytes, monocytes/macrophages (MM), HLA-DR antigens, C5b-9, and adhesion molecules such as alpha3beta1, LFA-1beta, and ICAM-1. RESULTS: In the glomeruli, C5b-9 deposits showed a significant correlation with the intensity of IgG and C3 deposition. The stage of the disease had a significant negative relationship with the glomerular alpha3beta1 expression. In the tubulointerstitium (TIN), the number of HLA-DR(+) cells was highly correlated with the numbers of total T lymphocytes, MM, and LFA-1beta(+) cells, as well as with the percentage of tubules with C5b-9 deposits. The extent of ICAM-1 expression in the TIN was significantly correlated with the numbers of interstitial MM, HLA-DR(+), and LFA-1beta(+) cells, as well as with the extent of tubular C5b-9 deposition. The severity of tubular atrophy and interstitial fibrosis had a relationship with the numbers of total T lymphocytes, MM, HLA-DR(+), and LFA-1beta(+) cells and with the extent of tubular C5b-9 deposition and ICAM-1 expression in the TIN. Serum creatinine (Scr) was highly correlated with the numbers of interstitial total T lymphocytes, MM, HLA-DR(+), and LFA-1beta(+) cells. Moreover, Scr had a significant relationship with the severity of tubular atrophy and interstitial fibrosis, as well as with the extent of tubular C5b-9 deposition and ICAM-1 expression in the TIN. Proteinuria was significantly correlated with the extent of tubular alpha3beta1 expression. CONCLUSIONS: In IMN, C5b-9 formation may be secondary to IgG and C3 deposition. Proteinuria may contribute to the TIN damage by altering the expression of alpha3beta1 integrins in tubular cells. De novo ICAM-1 and C5b-9 expression within the TIN as well as the activated interstitial cells may be important factors leading to renal damage and renal function impairment.