Glomerular C4d Deposition Research Articles

Urinary C4d and progression of kidney disease in IgA vasculitis.

Immunoglobulin A (IgA) vasculitis nephritis (IgAVN) is the most common secondary IgA nephropathy (IgAN). Urinary C4d have been identified associated with the development and progression in primary IgAN; however, its role in kidney disease progression of IgAVN is still unclear. This study enrolled 139 patients with IgAVN, 18 healthy subjects, 23 focal segmental glomerulosclerosis patients and 38 IgAN patients. Urinary C4d levels at kidney biopsy were measured using enzyme-linked immunosorbent assay. The association between urinary C4d/creatinine and kidney disease progression event, defined as 40% estimated glomerular filtration rate decline or end-stage kidney disease, was assessed using Cox proportional hazards models and restricted cubic splines. The levels of urinary C4d/creatinine (Cr) in IgAVN and IgAN patients were higher than in healthy controls. Higher levels of urinary C4d/Cr were associated with higher proteinuria and severe Oxford C lesions, and glomerular C4d deposition. After a median follow-up of 52.79 months, 18 (12.95%) participants reached composite kidney disease progression event. The risk of kidney disease progression event was higher with higher levels of Ln(urinary C4d/Cr). After adjustment for clinical data, higher levels of urinary C4d/Cr were associated with kidney disease progression in IgAVN [per Ln-transformed urinary C4d/Cr, hazard ratio 1.573, 95% confidence interval (CI) 1.101-2.245; P=.013]. Compared with the lower C4d/Cr group, the hazard ratio was 5.539 (95% CI 1.135-27.035; P=.034) for the higher levels group. Higher levels of urinary C4d/Cr were associated with kidney disease progression event in patients with IgAVN.

Association between glomerular C4d deposition, proteinuria, and disease severity in children with IgA nephropathy.

C4d may be used as a marker to evaluate the condition and prognosis of adults with IgA nephropathy, but there have been few studies of children with IgA nephropathy. C4d immunohistochemical staining was performed on samples from children with IgA nephropathy with C1q-negative immunofluorescence. The clinical and pathological treatment and prognostic characteristics of children in the C4d-positive and -negative groups were compared. A total of sixty-five children with IgA nephropathy were included in the study and were followed up for an average of 37months. C4d was mainly deposited along the capillary loops. The urinary protein-to-creatinine ratio (UPCR) in the C4d-positive group was significantly higher than that in the C4d-negative group (3.97 vs. 0.81, P < 0.001), and the average integrated optical density value of each child was positively correlated with the UPCR (r = 0.441, P < 0.001). There was a significant difference in the proportions of children with mesangial hypercellularity (M1) (68.97% vs. 44.44%, P = 0.048) and segmental glomerulosclerosis (S1) (65.52% vs. 33.33%, P = 0.010) between the C4d-positive group and the C4d-negative group. The proportion of children who received immunosuppressants in the C4d-positive group was higher than that in the C4d-negative group (86.21% vs. 36.11%, P < 0.001). There was no significant difference in the proportion of children developing kidney failure between the two groups. C4d was found to be associated with proteinuria, segmental lesions, and immunosuppressant treatment. Activation of the lectin pathway may reflect the severity of clinical and pathological manifestations of IgA nephropathy in children. A higher resolution version of the Graphical abstract is available as Supplementary information.

Clinical relevance of glomerular C4d deposition in children with early IgA nephropathy or Henoch-Schönlein purpura nephropathy.

Both IgA nephropathy (IgAN) and Henoch-Schönlein purpura nephropathy (HSPN) are characterized by glomerular mesangial IgA deposition. Several large studies on adults have suggested that glomerular C4d deposition has prognostic value in IgAN. However, there are few relevant studies on the clinical value of C4d deposition in children with IgAN or HSPN. We performed a retrospective cohort study in pediatric patients with IgAN or HSPN. Clinicopathological data were collected at the time of kidney biopsy. Kidney C4d deposition was analyzed by immunohistochemistry. The end point was defined as a ≥ 20% decrease in estimated glomerular filtration from baseline. We enrolled 75 children, including 36 children with IgAN and 39 with HSPN. The prevalence of C4d deposition was 36% (27/75). C4d deposition was more abundant in children with proteinuria ≥ 50mg/kg/day (51.9% versus 20.8%, P = 0.006) or nephrotic syndrome (37.0% versus 10.4%, P = 0.006). Mesangial hypercellularity (hazard ratio [HR], 5.745, 95% confidence interval [CI], 1.670-19.761, P = 0.006) and IgM deposition (HR, 4.522, 95% CI, 1.321-15.478, P = 0.016) were associated with C4d deposition. After a median follow-up of 22months, seven (19.4%) IgAN patients and one (2.6%) HSPN patient had decreased kidney function. In children with IgAN, positive C4d was associated with decreased kidney function (P = 0.047). Glomerular C4d deposition was associated with mesangial hypercellularity and glomerular IgM deposition in IgAN and HSPN. Glomerular C4d deposition may be a risk factor for eGFR decline in children with IgAN. A higher resolution version of the Graphical abstract is available as Supplementary information.

Prognostic Value of C4d Immunolabelling in Adult Patients With IgA Vasculitis.

Background and Objectives: Glomerular C4d deposits are associated the severity and outcomes of IgA nephropathy. Whether this holds true in immunoglobulin A vasculitis (IgAV) is not known. The main objective of the study was to analyze the prognostic value of glomerular C4d immunolabelling on kidney impairment in adults with IgAV.Design, Setting, Participants, Measurements: This retrospective cohort study included 120 adults with IgAV and a kidney biopsy performed between 1995 and 2018 in two French university hospital centers. All paraffin-embedded biopsies were reassessed according to Oxford classification. Immunofluorescence for C4d was performed in all cases. For analysis, patients were grouped according to positivity for C4d in the glomerular area. The main outcome was a composite endpoint of 50% increase in 24 h-proteinuria, or eGFR decrease by 50%, or kidney replacement therapy.Results: The median follow-up was 28.3 months. Twenty-three patients met the composite endpoint, 12 for kidney replacement therapy, 6 for an eGFR decrease >50% and 5 for a >50% increase in proteinuria. At time of biopsy, the median proteinuria was 1.9 g/24 h and the median eGFR 73.5 mL/min/1.73 m2. Among the 102 patients evaluable for C4d, 24 were positive on >30% glomeruli, mainly with a parieto-mesangial pattern. In this group, the initial proteinuria was more frequently nephrotic than in the C4d– group (60% vs. 33%, P = 0.039). Mesangial hypercellularity was more frequent in the C4d+ group (42% vs. 13%; P = 0.006) whereas macroscopic hematuria was more frequent in the C4d– group (18% vs. 0%; P = 0.03). After a median follow-up of 28 months, kidney survival did not differ according to C4d status.Conclusion: In a population of adult IgAV patients, glomerular positivity for C4d was associated with the severity of the kidney disease at presentation, but not with subsequent renal function deterioration.

Complement Activation Is Associated With Crescents in IgA Nephropathy.

IntroductionCrescents, especially those found at a percentage greater than 50%, are often associated with rapid progression of kidney disease in IgA nephropathy (IgAN). The mechanism of crescents forming in IgAN is still unclear. In this study, we aimed to evaluate whether excess complement activation participates in the formation of crescents in IgAN.MethodsOne hundred IgAN patients with various proportions of crescents—24 with 1%–24%, 27 with 25%–49%, 21 with 50%–74% 12 with more than 75%, and 16 without crescents—were included. Urinary concentrations of mannose-binding lectin (MBL), Bb, C4d, C3a, C5a, and soluble C5b-9 (sC5b-9) were measured at the time of biopsy. Receiver operating characteristic (ROC) curves were performed to evaluate predictive ability of renal survival for urine complement activation. In addition, historical C4d, C5b-9, and C3d were stained by immunohistochemistry.ResultsIgAN patients with more than 50% crescent formation showed higher complement activation levels than the other patients (urinary C3a/creatinine (C3a/Cr): 6.7295 ng/mg, interquartile range (IQR) 1.4652–62.1086 ng/mg vs. 0.1055 ng/mg, IQR 0–1.4089 ng/mg; urinary C5a/Cr: 15.6202 ng/mg, 4.3127–66.7347 ng/mg vs. 0.3280 ng/mg, IQR 0.0859–2.4439 ng/mg; urinary sC5b-9/Cr: 98.6357 ng/mg, 8.8058–1,087.4578 ng/mg vs. 1.4262 ng/mg, 0.0916–11.0858 ng/mg, all p-values <0.001). The levels of urinary MBL and C4d representing lectin complement pathway showed a linear association with the proportion of crescents (r = 0.457 and 0.562, respectively, both p-values <0.001). Combined urine complement products could increase the predictive ability compared with crescents alone from 0.904 to 0.944 (p = 0.062) with borderline significance. Moreover, the glomerular C4d deposition rate elevated with the increase of proportions of crescents.ConclusionExcess complement activation may be involved in the formation of crescents, especially diffuse crescent formation, in patients with IgAN. Urinary C4d correlated with the proportion of crescents and was a potential biomarker for disease monitoring in crescentic IgAN.

Glomerular C4d Deposition and Kidney Disease Progression in IgA Nephropathy: A Systematic Review and Meta-analysis

BackgroundGlomerular deposition of C4d is a widely used biomarker for activation of the lectin pathway in the complement system and is reported to be associated with kidney progression in immunoglobulin A nephropathy (IgAN). The aim of this study was to evaluate whether glomerular C4d deposition, as a new biomarker, improves the prediction of kidney prognosis in IgAN.Study DesignSystematic review and meta-analysis.Setting & PopulationPatients with biopsy-proven primary IgAN without age limitations.Selection Criteria for Studies: Cross-sectional or cohort studies reporting the prevalence of glomerular C4d deposition or evaluating its association with IgAN progression.PredictorGlomerular C4d deposition.OutcomeComposite progression event of a >30% decline in estimated glomerular filtration rate or end-stage kidney disease.Results12 studies with 1,251 patients were included. The prevalence of glomerular C4d deposition was 34% (95% CI, 27%-41%), with large heterogeneity (I2 = 86%; P < 0.001). Patients with C4d deposition had lower estimated glomerular filtration rates (mean difference [MD], −11.48; 95% CI, −18.27 to −4.70; P < 0.001) as well as higher urinary protein-creatinine ratios (MD, 0.87; 95% CI, 0.53-1.21; P < 0.001) or 24-hour urinary protein excretion (MD, 0.99; 95% CI, 0.50-1.47; P < 0.001) and higher risk for hypertension (relative risk [RR], 1.45; 95% CI, 1.06-1.99; P = 0.02) than patients without C4d deposition. Glomerular C4d deposition was associated with a high Oxford classification score, including M1, E1, S1, and T1/2 lesions (all P ≤ 0.006). Patients with C4d deposition had higher rates of use of renin-angiotensin system blockers and immunosuppressants. Glomerular C4d was found to be a risk factor for the composite kidney event (RR, 3.17; 95% CI, 2.29-4.40; P < 0.001; adjusted HR, 2.05; 95% CI, 1.53-2.76; P < 0.001) and end-stage kidney disease (RR, 4.37; 95% CI, 3.15-6.07; P < 0.001) without evidence of heterogeneity.LimitationsThe definition of positive C4d was not uniform and not all studies provided data about kidney outcomes.ConclusionsGlomerular C4d deposition is associated with an adverse prognosis and may be a useful biomarker of disease prediction in IgAN.

Relevance of glomerular C4d deposition in pediatric patients with Henoch-Schönlein Purpura compared to IgA nephritis

Introduction: IgA nephropathy (IgAN) is the most common primary glomerulonephritis (GN) in western countries and Henoch-Schonlein purpura nephritis (HSPN) is the most common form of vasculitis in childhood. Renal biopsy findings in both nephropathies are often similar and are characterized by mesangioproliferative GN with mesangial or mesangiocapillary IgA and C3c deposits. Objectives: The aim of this study was to investigate the significance of glomerular C4d-deposition as a discriminating factor between pediatric HSPN and IgAN. Patients and Methods: We retrospectively analyzed patient records and renal biopsies from 53 pediatric patients from one single center with a median age of 10.5 years (range 2.3-18 years). Twenty-two patients suffered from IgAN and 31 from HSPN. Work-up of all renal biopsies was performed using standard protocols including immunohistochemistry for C4d. Results: Pediatric IgAN patients presented significantly more often with gross hematuria, higher serum creatinine, lower glomerular filtration rate, lower serum C3 and proteinuria and on histology less endocapillary hypercellularity compared to HSPN patients. However, the rate of glomerular C4d-positivity was not different between IgAN (36%) and HSPN (42%). Comparing all cases with positive versus negative glomerular C4d-staining, pediatric patients with glomerular C4d-positivity showed significantly lesser gross hematuria and received significantly more often cyclophosphamide. This was in line with a tendency towards more proteinuria, hypertension and renal insufficiency at last follow-up in C4d-positive compared to C4d-negative patients. Conclusion: In conclusion, in our monocentric study glomerular C4d does not differ between pediatric HSPN and IgAN, but was associated with a tendency to a more severe course of the disease that needs to be confirmed in larger multicentric studies.

Glomerular C4d in Post-Transplant IgA Nephropathy is associated with decreased allograft survival

BackgroundGlomerulonephritis (GN), including post-transplant IgAN (post-Tx IgAN) is an important contributor to decreased long-term allograft survival. The immunopathological detection of the complement degradation product C4d in glomeruli (C4dG) has been recently described as a risk factor in native kidney IgAN, however little is known about C4dG deposition in post-Tx IgAN. We hypothesized that glomerular C4d may indicate a more aggressive disease course and worse allograft survival in patients with post-Tx IgAN.MethodsIn this retrospective study we assessed the presence and clinical relevance of C4dG in patients with post-transplant IgAN. We analyzed 885 renal allograft recipients, including 84 patients with post-transplant GN. All patients were transplanted between January 1999 and April 2006 and underwent at least one biopsy for differnt causes. The primary endpoint was death-censored graft survival, with a median follow-up of 9.6 (IQR 3.8–13.2) years.ResultsThe prevalence of post-Tx GN was 9.5%. Twenty-seven patients with post-Tx IgAN were included. C4dG positive patients (N = 18, 66.7%) had significantly worse allograft survival compared to C4dG negative post-Tx IgAN patients and patients without post-Tx IgAN [C4dG positive: 27.8% vs. 55.6% and 66.0%; log-rank: p = 0.01]. C4dG remained a significant risk factor (HR 2.22, 95% CI 1.27–3.87) for allograft loss even after adjustment for T cell mediated rejection (TCMR) and antibody mediated rejection.ConclusionGlomerular C4d deposition is an independent risk factor for worse graft-survival in patients with post-Tx IgAN, even after adjusting for other risk factors such as antibody mediated rejection. Assessment of glomerular C4d deposition may provide a valuable prognostic risk assessment tool to identify high risk patients in post-Tx IgAN.Graphic abstract

Mesangial C4d deposition at diagnosis in childhood immunoglobulin A nephropathy.

Immunoglobulin A nephropathy (IgAN) is a major cause of end-stage renal disease. Complement activation via the lectin pathway influences outcomes in IgAN. We examined the association of glomerular C4d deposition with clinicopathological severity at diagnosis and the disappearance of proteinuria in Japanese pediatric IgAN patients. We retrospectively analyzed 25 children newly diagnosed with IgAN at Hokkaido University Hospital. We evaluated glomerular C4d immunofluorescent staining at diagnosis. We compared clinical findings, pathological findings (based on Oxford classification), and the disappearance of proteinuria within 24months after renal biopsy between C4d-positive and C4d-negative patients. Glomerular C4d staining was observed in 14 patients (56.0%). C4d-positive patients had significantly higher proteinuria at diagnosis than C4d-negative patients (2.03g/gCr vs 0.78g/gCr; P = 0.005). The number of glomeruli with segmental glomerulosclerosis or adhesion (8.0% vs 0.0%; P = 0.046) and the extent of tubular atrophy/interstitial fibrosis (9.46% vs 2.86%; P = 0.031) were significantly increased in C4d-positive patients compared with C4d-negative patients. Further, the proportion of patients with modified T1 (>10%) was significantly higher in the C4d-positive group than the C4d-negative group. There was no significant difference, however, in the disappearance rate of proteinuria at 24months after renal biopsy between groups (64% vs 82%; P = 0.149). Glomerular C4d deposition was associated with clinicopathological severity at diagnosis in Japanese pediatric patients with IgAN. Glomerular C4d deposition, however, was not a predictor of the disappearance of proteinuria within 24months after diagnosis in Japanese pediatric patients with IgAN.

Combination of Glomerular C4d and Morphologic Glomerular Lesions as a Possible Indicator in the Diagnosis of Acute or Chronic Active Antibody-Mediated Rejection

BackgroundLinear C4d staining in the peritubular capillaries is considered a sensitive and useful marker of active or chronic active antibody-mediated rejection (ABMR) in transplanted kidneys. However, the diagnostic significance of glomerular C4d deposits (gC4d) is still undetermined. The aim of this study is to evaluate the association of gC4d with clinicopathologic features and to assess its diagnostic value. MethodsFrom 2013 to 2018, a total of 158 cases of allograft kidney biopsy specimens were obtained from the Korea University Anam Hospital. The histologic features were evaluated according to the Banff classification. The gC4d were determined through immunohistochemical analyses and classified based on scores of 0 to 3 according to the extent of gC4d. ResultsA total of 73 cases (46.2%) showed gC4d, and 37 cases (23.4%), 23 cases (14.6%), and 13 cases (8.2%) were classified with a score of 1+, 2+, and 3+, respectively. The gC4d showed a significant correlation with antibody-associated histologic lesions, including peritubular capillaritis, glomerulitis, and transplant glomerulopathy (P < .001). However, gC4d showed no significant association with cell-mediated injuries such as tubulitis, interstitial inflammation, acute tubular necrosis, and thrombotic microangiopathy. Although positive gC4d alone was associated with nonspecific findings without ABMR, most cases of gC4d combined with glomerulitis or transplant glomerulopathy showed typical histologic features of ABMR, clinically with higher antibody titers and severe functional deterioration. ConclusionsGlomerular C4d deposits may be an alternate useful marker in the diagnosis of active or chronic active ABMR when combined with histologic features of glomerular lesions.

Glomerular C4d deposition can precede the development of focal segmental glomerulosclerosis

Recent studies suggest that complement plays a role in the pathogenesis of focal segmental glomerulosclerosis (FSGS). Moreover, co-localization of IgM and C3 deposits with FSGS lesions has frequently been reported. Here, we investigated whether glomerular complement deposition precedes the development of FSGS and whether it represents local complement activation. Renal biopsies from 40 patients with primary FSGS, 84 patients with minimal change disease, and 10 healthy individuals were stained for C4d, C1q, and mannose-binding lectin. C4d deposits were also measured in renal allograft biopsies from 34 patients with native primary FSGS, 18 of whom subsequently developed recurrent FSGS. Lastly, we measured C4d deposits in the Munich Wistar Frömter rat model of FSGS. The prevalence of C4d-positive glomeruli was significantly higher among patients with FSGS (73%) compared to patients with minimal change disease (21%) and healthy individuals (10%). Moreover, segmental sclerosis was absent in 42% of C4d-positive glomeruli. Glomerular C1q was significantly more prevalent in FSGS compared to minimal change disease or healthy individuals, while mannose-binding lectin was infrequently observed. C4d deposition was significantly more prevalent in recurrent FSGS (72%) before the development of sclerotic lesions compared to control transplant samples (27%). Finally, at the onset of albuminuria but before the development of FSGS lesions, Munich Wistar Frömter rats had a significantly higher percentage of C4d-positive glomeruli (31%) compared to control rats (4%). Thus, glomerular C4d deposition can precede the development of FSGS, suggesting that complement activation may play a pathogenic role in the development of FSGS.

Utility of C4D deposits in native renal diseases and relation with disease progression

INTRODUCTION: C4D is a well-known biomarker of complement cascade. The utility of C4D in identification of antibody-mediated rejection has been known since its incorporation in Banff classification in 2003. Recently, many researchers have turned their attention to C4D deposition in native renal diseases. The present study was done at our tertiary care center to adjudge the significance of C4D deposits in native renal diseases across Indian cohort of patients. MATERIALS AND METHODS: A retrospective study was done on fifty cases of native renal diseases and followed up at 6 months. C4D immunohistochemical analysis was performed on formalin-fixed paraffin-embedded renal tissue sections with antibody against C4D (polyclonal rabbit immunoglobulin G antihuman C4D antibody). RESULTS: All cases of membranous nephropathy, immunoglobulin A nephropathy, and hypertensive nephropathy showed glomerular C4D positivity ranging from 2+ to 3+. Nearly 50%, 50%, 43%, and 40% cases of diabetic nephropathy, membranoproliferative glomerulonephritis, lupus nephritis, and postinfectious glomerulonephritis, respectively, demonstrated positive glomerular C4D deposits. Increased intensity expression of glomerular C4D deposits was in significant concordance with presenting 24 h urinary protein level at the time of biopsy and in follow-up trends; C4D positive cases were noted to have slowed recovery process as evidenced by delay in returning to normal range proteinuria. Higher histological grades in respective native diseases' classification correlated with increased glomerular C4D intensity expression. C4D positivity in other renal compartments did not yield any significant results. CONCLUSION: C4D positivity can be explored as a diagnostic and prognostic tool in native renal diseases as well, apart from transplant biopsies' evaluation

Erythrocyte and glomerular C4d deposits as a biomarker for active lupus nephritis

IntroductionLupus nephritis (LN) is a serious manifestation of systemic lupus erythematosus (SLE) and histologically evident even in those without clinical manifestations of renal disease. Aim of the workTo assess C4d on erythrocytes (E-C4d) and glomerular deposits (G-C4d) in SLE patients and study its association to LN and disease activity. Patients and methods: 61 subjects were enrolled including 15 with LN (study group); 15 with renal disease not due to SLE (control A group); 16 SLE patients with no renal affection (control B group) and 15 healthy individuals (control C group). Flow cytometry system was used for C4d immunohistochemical staining. SLE disease activity index (SLEDAI) was assessed for SLE patients. ResultsThe age was comparable among groups; for LN patients was 28.3±8.2years; group A (35.9±13.3); group B (27.1±8.8) and group C (29.4±7.1) (p=.06). Patients were mostly females. The disease duration of LN patients was 1–2years; group A (3–5years) and group B (5–10years). E-C4d and G-C4d deposits were significantly higher in LN patients (8.08±2.93 and 2.3±0.97) in comparison to the control groups (A/B/C) (A: 3.78±0.38 and 0.6±1.12; B: 3.72±0.32; C: 3.55±0.44 p<.001, p<.001, p<.001 MFI respectively). E-C4d and G-C4d significantly correlated with LN activity (r=0.8, p<.001 and r=0.7, p=.005) and with SLEDAI (r=0.9, p=.005 and r=0.8, p=.002, respectively). ConclusionErythrocytic C4d correlated significantly with the LN activity which might serve as a potential biomarker for renal activity in the future instead of biopsy and may further help in the optimum follow up of LN patients.

Complement Activation in Patients With Diabetic Nephropathy

IntroductionComplement activation plays a role in various organs in patients with diabetes. However, in diabetic nephropathy (DN), the role of complement activation is poorly understood. We examined the prevalence and clinical significance of complement deposits in the renal tissue of cases with type 1 and type 2 diabetes with and without DN.MethodsWe measured the prevalence of glomerular C4d, C1q, mannose-binding lectin (MBL), and C5b-9 deposits in 101 autopsied diabetic cases with DN, 59 autopsied diabetic cases without DN, and 41 autopsied cases without diabetes or kidney disease. The presence of complement deposits was scored by researchers who were blinded with respect to the clinical and histological data.ResultsC4d deposits were more prevalent in cases with DN than in cases without DN in both the glomeruli (46% vs. 26%) and the arterioles (28% vs. 12%). C1q deposits were also increased in the glomerular hili (77% vs. 55%) and arterioles (33% vs.14%), and were correlated with DN (P < 0.01). MBL deposits were only rarely observed. C5b-9 deposits were more prevalent in the cases with diabetes mellitus (DM) than in the cases without DM (69% vs. 32%; P < 0.001). Finally, glomerular C4d and C5b-9 deposits were correlated with the severity of DN (ρ = 0.341 and 0.259, respectively; P < 0.001).ConclusionComplement activation is correlated with both the presence and severity of DN, suggesting that the complement system is involved in the development of renal pathology in patients with diabetes and is a promising target for inhibiting and/or preventing DN in these patients.

Glomerular C4d deposits can mark structural capillary wall remodelling in thrombotic microangiopathy and transplant glomerulopathy: C4d beyond active antibody-mediated injury: a retrospective study.

Peritubular capillary C4d (ptc-C4d) usually marks active antibody-mediated rejection, while pseudolinear glomerular capillary C4d (GBM-C4d) is of undetermined diagnostic significance, especially when seen in isolation without concurrent ptc-C4d. We correlated GBM-C4d with structural GBM abnormalities and active antibody-mediated rejection in 319 renal transplant and 35 control native kidney biopsies. In kidney transplants, ptc-C4d was associated with GBM-C4d in 97% by immunofluorescence microscopy (IF) and 61% by immunohistochemistry (IHC; P < 0.001). Transplant glomerulopathy correlated with GBM-C4d (P < 0.001) and presented with isolated GBM-C4d lacking ptc-C4d in 69% by IF and 40% by IHC. Strong isolated GBM-C4d was found post year-1 in repeat biopsies with transplant glomerulopathy. GBM-C4d staining intensity correlated with Banff cg scores (rs = 0.45, P < 0.001). Stepwise exclusion and multivariate logistic regression corrected for active antibody-mediated rejection showed significant correlations between GBM duplication and GBM-C4d (P = 0.001). Native control biopsies with thrombotic microangiopathies demonstrated GBM-C4d in 92% (IF, P < 0.001) and 35% (IHC). In conclusion, pseudolinear GBM-C4d staining can reflect two phenomena: (i) structural GBM changes with duplication in native and transplant kidneys or (ii) active antibody-mediated rejection typically accompanied by ptc-C4d. While ptc-C4d is a dynamic 'etiologic' marker for active antibody-mediated rejection, isolated strong GBM-C4d can highlight architectural glomerular remodelling.

The clinical implications of the unique glomerular complement deposition pattern in transplant glomerulopathy.

The etiology and treatment of transplant glomerulopathy (TG) is not clear. TG is associated with donor-specific antibodies but the lack of C4d deposition in the peritubular capillaries (ptc-C4d) in some cases has caused the role of complement in the pathogenesis of TG to be debated. There is however, little information on C4d deposition in the glomerulus itself. We retrieved random frozen sections from 25 cases with well-established TG by light microscopy (LM) and 25 cases without TG as controls and reviewed the LM and immunofluorescence (nine biopsies were excluded due to inadequate samples). Glomerular complement deposition was assessed in all included biopsies. Glomerular C3d and C4d deposition occurred in a distinct pattern in all TG biopsies: segmental or global double linear staining of the glomerular capillary wall in 23 (100%). This pattern was not present in any NON-TG biopsies. The distinct glomerular complement deposition patterns in all TG cases are suggestive that TG is a proximal complement-mediated process and therapies should focus on proximal complement inhibition.

IgA nephropathy: association of C4d with clinical and histopathological findings and possible role of IgM

Background: In patients with IgA nephropathy (IgAN) lectin and alternative pathways of the complement can be activated. Our aim was to analyze the association of glomerular and extraglomerular C4d staining—the representative of lectin pathway—with demographic, clinical and histopathological findings in primary IgAN patients. Design: Seventy-three patients were enrolled and after re-evaluation 37 of them were included in this study. Biopsies were analyzed for staining with anti-C4d primary monoclonal antibody by immunohistochemistry. Patients were classified as positive and negative groups based on their glomerular C4d deposition. Groups were compared for their baseline clinical and histopathological findings. Results: Sixteen (43.2%) of 37 patients were C4d-positive. Glomerular C4d-staining was associated with more severe proteinuria (2906 mg/day vs. 1091 mg/day; p = 0.002), lower GFR (54.87 mL/min vs. 95 mL/min; p = 0.023), higher blood pressure (p = 0.022), more severe endocapillary hypercellularity (p < 0.001) and more severe tubular atrophy (p < 0.01). Mesangial IgM deposition was found to be associated with glomerular C4d staining and nephrotic range proteinuria. Conclusions: Glomerular C4d deposition was found to be associated with more unfavorable histopathological and clinical findings at the time of diagnosis. Association of mesangial IgM deposition with the activation of lectin pathway is a novel finding. Mesangial IgM deposition in our patients may reflect the genetic heterology of IgAN between diverse populations. However, since these data are about association, a cause-and-effect about IgM and IgAN cannot be proven solely with these findings.

Clinical Implications

HomeHypertensionVol. 66, No. 1Clinical Implications Free AccessResearch ArticlePDF/EPUBAboutView PDFView EPUBSections ToolsAdd to favoritesDownload citationsTrack citationsPermissions ShareShare onFacebookTwitterLinked InMendeleyReddit Jump toFree AccessResearch ArticlePDF/EPUBClinical Implications Originally published1 Jul 2015https://doi.org/10.1161/HYPERTENSIONAHA.115.05813Hypertension. 2015;66:2Renal Complement Activation in Preeclampsia (page 117)Download figureDownload PowerPointA growing body of evidence suggests that complement dysregulation plays a role in the pathogenesis of preeclampsia. The kidney is one of the major organs affected in preeclampsia. Penning et al hypothesized that complement activation is involved in the kidney damage in preeclampsia. In this issue, they studied autopsied kidneys from 11 women with preeclampsia, 25 pregnant controls, and 14 nonpregnant controls with hypertension. The samples were immunostained for complement factors and immunoglobulins. All of the kidney sections obtained from the preeclamptic women contained glomerular C4d deposits in a predominantly global staining pattern. Furthermore, preeclampsia was associated with glomerular C1q and IgM, but not with mannose-binding lectin or properdin, indicating classical pathway activation. The results were validated in a soluble fms-like tyrosine kinase-1–induced preeclampsia mouse model. These mice developed excess glomerular C4 deposits and increased levels of circulating activated C3, indicating that preeclampsia-related renal complement activation is initiated by endothelial damage caused by angiogenic dysregulation. The results from this study suggest that inhibiting complement activation could be beneficial for preventing the renal manifestations of preeclampsia. The authors previously found increased classical pathway activation in the placentas of preeclamptic women. Inhibiting excessive complement activation may therefore be a promising therapeutic approach affecting multiple organ systems. However, further investigation is needed to establish the safety of complement inhibition during pregnancy.Mineralocorticoid Blockade and Aortic Stiffness (page 99)Women are normally protected against development of cardiovascular disease, but this protection is lost in conditions of insulin resistance, such as obesity and type 2 diabetes mellitus. Data from our laboratory, and that of others, suggest that consumption of a Western diet, high in fat and refined carbohydrates, and associated heightened tissue renin–angiotensin–aldosterone system activity results in attenuated nitric oxide–mediated vasodilation and increased vascular fibrosis and stiffness. This is consistent with clinical observations that obesity, insulin resistance, and diabetes mellitus are predisposing factors for development of vascular stiffness in both men and women. Our current study indicates that low doses of the mineralocorticoid receptor blocker spironolactone, which does not affect blood pressure, prevent Western diet–induced abnormalities in nitric oxide–mediated vasorelaxation and vascular stiffness in women (Figure). These findings have important clinical implications because vascular stiffness is a powerful predictor for the development of cardiovascular disease. Furthermore, these findings suggest that a strategy to reduce mineralocorticoid receptor signaling may be preventative and therapeutic in protecting against development of vascular disease in women.Download figureDownload PowerPointNeutrophil Gelatinase–Associated Lipocalin Mediates Mineralocorticoids Fibrotic Effects (page 158)Download figureDownload PowerPointMineralocorticoid receptor (MR) antagonists showed benefit in cardiovascular diseases, but their mode of action remains poorly understood. Underlying mechanisms may associate diuretic, antifibrotic, and anti-inflammatory effects. Clinical use of MR antagonists presents some limitations related to their renal potassium sparing effect that favors hyperkalemia in patients with renal dysfunction. Understanding the signaling pathways modulated by aldosterone and MR in cardiovascular diseases is required to identify novel targets and biomarkers of MR activation.In this issue, Tarjus et al report that a novel MR target, neutrophil gelatinase–associated lipocalin (NGAL), has a critical role in high blood pressure and cardiovascular remodeling induced by mineralocorticoid activation: preventing NGAL expression in a murine model blunted cardiovascular extracellular matrix deposition and increased blood pressure. In patients with stage B heart failure, plasma levels of the complex between NGAL and matrix metalloproteinase 9 correlated with fibrosis markers, such as procollagen type I N-terminal peptide. NGAL–matrix metalloproteinase 9 complex levels may be useful as biomarkers of MR activation to select patients prone to MR antagonists and therefore increasing the benefit/risk balance of this therapeutic class.These data also uncover a novel role of NGAL that has been considered until now as a marker of renal injury but may also have a mechanistic role in cardiovascular disease and beyond. NGAL may be a novel therapeutic target in hypertension and extracellular matrix deposition. Previous Back to top Next FiguresReferencesRelatedDetails July 2015Vol 66, Issue 1 Advertisement Article InformationMetrics © 2015 American Heart Association, Inc.https://doi.org/10.1161/HYPERTENSIONAHA.115.05813 Originally publishedJuly 1, 2015 PDF download Advertisement

Association of glomerular C4d deposition with various demographic data in IgA nephropathy patients; a preliminary study.

Background: IgA nephropathy (IgAN) is the most prevalent primary chronic glomerulopathy worldwide. Thus, it is of vital importance to search for factors aggravating the disease progress, monitor disease activity and predict disease-specific therapy. C4d is a well-known biomarker of the complement cascade with a potential to meet the above needs. Objectives: The aim of our study was, therefore, to determine whether C4d staining at the time of kidney biopsy had any correlation with the demographic, clinical and biochemical variables in IgAN. Patients and Methods: The definition of IgAN requires the presence of diffuse and global IgA deposits which were graded ≥2+ and weak C1q deposition. C4d immunohistochemical staining was conducted retrospectively on 29 renal biopsies of patients with IgAN, which were selected randomly from all biopsies. C4d immunohistochemical staining was performed on 3-μm deparaffinized and rehydrated sections of formaldehyde-fixed, paraffin-embedded renal tissues. Results: Of 29 selected patients, 68% were male. In this study, 54.2±25 percent of glomeruli in all biopsies were positive for C4d. The mean and standard deviation (SD) of serum creatinine and the magnitude of proteinuria were 1.72±1.2 mg/dl and 1582±1214 mg/day, respectively. In this study, we observed statistically significant correlations of percent C4d positivity with the serum creatinine (r=0.61, p=0.0005), magnitude of proteinuria (r=0.72, p=0.0001), the proportion of globally sclerotic glomeruli (r=0.43, p=0.02) and the proportion of tubulointerstitial fibrosis (r=0.54, p=0.0023). Conclusions: The results from our investigation on C4d positivity in biopsy-proven cases of IgAN are in accord with some of the previous studies. These findings, however, require further validation in larger samples.

Glomerular miRNA Expression in the Fischer to Lewis Rat Model of Acute Humoral Rejection.

Acute humoral rejection is currently the most important diagnostic and therapeutic problem in renal transplantation. The Fischer to Lewis rat model is a well established model of acute humoral rejection due to MHC and non-MHC alloantibodies. In order to identify diagnostically useful glomerular miRNA expression patterns and to identify novel pathogenetic concepts and therapeutic targets we quantififed the glomerular miRNA expression of this model. 6 weeks after life-sustaining transplantation without immunosuppression 8 allografts were harvested for histologic examination and glomerular miRNA quantification by RT-PCR. Histologic changes and miRNA expression patterns were correlated and compared to 8 isografts. Glomerular capillaries contained significantly more monocytes in allografts than in isografts, consistent with transplant glomerulitis. In allograft glomeruli miR-451 and miR-192 were significantly downregulated compared to isografts. Both were inversely correlated with glomerular C4d deposition and monocyte content. With miR-192 and miR-451 we identified two micro-RNAs which are downregulated in the glomeruli of a rat model of acute humoral rejection. Whereas little is known about miR-192, miR-451 is known to be involved in inflammation. Both could be valid target molecules in acute humoral rejection. Our next projects will determine the exact cell type expressing both miRNAs, their relevance for human acute humoral rejection, their function and potential as therapeutic targets.