Complement deposition, C4d, on platelets is associated with vascular events in systemic lupus erythematosus

OBJECTIVE

Complement components, including C4d, can be found on activated platelets, a process associated with vascular disease in SLE. We investigated whether platelet C4d (PC4d) adds additional value to traditional and known lupus-associated risk factors when identifying SLE patients with vascular disease.

METHODS

This cross-sectional study included 308 well-characterized SLE patients and 308 matched general population controls. PC4d deposition was analysed using flow cytometry. Values >95% of controls were considered as PC4d positive (+). aPL were determined by Luminex, and the LA test was performed by DRVVT. History of vascular disease (composite and as separate outcomes) was defined at inclusion.

RESULTS

SLE patients had increased PC4d deposition as compared with population controls (50 vs 5%, P < 0.0001). PC4d+ positively associated with any vascular events, and separately with venous and cerebrovascular events, and also with all investigated aPL profiles. The association for any vascular event remained statistically significant after adjustment for traditional and SLE-associated risk factors (odds ratio: 2.3, 95% CI: 1.3, 4.3, P = 0.008). Compared with patients negative for both PC4d and LA, patients with double positivity were more likely to have vascular disease (odds ratio: 12.3, 95% CI: 5.4, 29.3; attributable proportion due to interaction 0.8, 95% CI: 0.4, 1.1).

CONCLUSION

PC4d+ is associated with vascular events in SLE, independently of traditional and SLE-associated risk factors. Concurrent presence of PC4d and LA seem to interact to further increase the odds for vascular events. Prospective studies should examine whether the aPL/PC4d combination can improve prediction of vascular events in SLE and/or APS.

Rethinking fibrinogen storage disease of the liver: ground glass and globular inclusions do not represent a congenital metabolic disorder but acquired collective retention of proteins

Three types of intracytoplasmic inclusions immunoreactive to fibrinogen are collectively diagnosed as hepatic fibrinogen storage disease. This study aimed to better characterize ground glass (type II) and globular (type III) fibrinogen inclusions by the pathological examination of 3 cases and a literature review. Three adults (age: 32-64 years; male/female = 2:1) were unexpectedly found to have fibrinogen-positive ground glass changes (type II inclusions) by liver needle biopsy, against a background of acute hepatitis E, resolving acute cholangitis, or severe lobular hepatitis of unknown etiology. One patient also had fibrinogen-positive intracytoplasmic globules (type III inclusions) in the first biopsy, but they were not present in a second biopsy. None had coagulation abnormalities or hypofibrinogenemia. On immunostaining, both inclusions were strongly positive for not only fibrinogen but also C-reactive protein and C4d. Ultrastructurally, ground glass changes corresponded to membrane-bound cytoplasmic inclusions containing amorphous, granular material. The pathological features of type II fibrinogen inclusions were identical to those of pale bodies in hepatocellular carcinoma. The literature review suggested that type I fibrinogen inclusions characterized by a polygonal appearance are strongly associated with mutations in fibrinogen genes, coagulopathy, and family history, whereas type II/III inclusions are immunoreactive to multiple proteins and typically develop in cases of other unrelated liver diseases. In conclusion, type II and III fibrinogen inclusions do not represent a true hereditary storage disease but instead the collective retention of multiple proteins. Given the lack of clinical significance, a less specific name (e.g., pale body) may be more appropriate for those inclusions.

Diagostic Accuracy of C4d-IHC in Diagnosis of MGN

INTRODUCTION

Membranous glomerulonephritis (MGN) is the most common cause of nephrotic syndrome in adults. The gold standard techniques for diagnosis of MGN are based on a constellation of findings given by light microscope, electron microscope (EM), and immunofluorescence (IF). Occasionally, only formalin-fixed tissues are available for the analysis by light microscopy, which have limitations in differentiating minimal change diseases from MGN. Recently, the usage of C4d immunohistochemistry (IHC) has been proposed for the diagnosis of MGN. The aim of this study was to evaluate the accuracy of C4d-IHC in diagnosis of MGN.

METHODS

The present investigation conducted on patients with nephrotic syndrome who underwent renal biopsy in Labbafinejad hospital, from 2016 to 2017. The entire specimens were examined by light microscope, immunofluorescence, and electron microscope as a gold standard method for diagnosis of MGN. The samples were then stained for C4d immunohistochemical analysis. Eventually, the sensitivity, specificity, positive, and negative predictive value for C4d-IHC was determined.

RESULTS

The sensitivity and specificity of the C4d-IHC in order to differentiate MGN from other glomerulopathies were 95% and 87.5%, respectively. In addition, the negative and positive predictive values were 97.2% and 79.16%, respectively.

CONCLUSION

It was ultimately attained that C4d-IHC has more accuracy in identification and diagnosis of MGN, in contrary to EM and IF, this method is more usable and cost effective, which requires a lower level of skill and advanced equipment. Indeed, this technique does not require fresh specimen.

Morphological characterization of chronic antibody-mediated rejection in ABO-identical or ABO-compatible pediatric liver graft recipients

This study aims to define the morphological profile associated with the presence of donor-specific antibodies (DSAs) and/or C4d immunostaining in ABO-identical or compatible pediatric liver grafts. Ten-year protocol liver graft biopsies performed at 131.3 ± 15.3 months after transplantation in 53 pediatric liver graft recipients were reviewed. Immunostaining for C4d was systematically performed and semiquantitatively analyzed. DSAs were concurrently quantified, and results were available for 44 patients. All biopsies demonstrated fibrotic changes with a mean liver allograft fibrosis score (LAFSc) of 5.1 ± 2.2. A total of 31 (58%) biopsies exhibited C4d positivity. DSAs were detected in 20 (45%) patients, and mean maximal mean fluorescence intensity was 12,977 ± 6731. LAFSc (6.3 ± 1.3 versus 3.9 ± 2.2; P = 0.008), perivenular fibrosis (2.7 ± 0.5 versus 1.3 ± 1.0; P < 0.001), and portal inflammation (1.4 ± 0.8 versus 0.3 ± 0.5; P = 0.009) were significantly higher in the double-DSA and C4d-positive group versus the double-negative group. We defined a histological scoring system from these results, which was integrated with the 2016 Banff definition and allowed reclassifying patients for the diagnosis of chronic active antibody-mediated rejection (cAMR; 11/53 versus 13/53). Diagnoses of probable cAMR according to Banff 2016 (n = 4) were unchanged, but 2 among the 9 patients classified as possible cAMR according to the 2016 Banff definition were excluded for this diagnostic when using our histological score. In conclusion, our results confirmed that perivenular fibrosis and portal inflammation in late pediatric liver graft biopsies are features of cAMR. Our histological score could improve the accuracy of the 2016 Banff definition for the diagnosis of cAMR. Liver Transplantation 24 897-907 2018 AASLD.

Mesangial C4d Deposits in Early IgA Nephropathy

BACKGROUND AND OBJECTIVES

The prognostic value of mesangial C4d deposits in IgA nephropathy has been analyzed in patients with reduced GFR but has not been analyzed in those with normal kidney function. The main objective of the study was to analyze the prognostic value of C4d deposits and association with response to treatment in patients with IgA nephropathy and normal GFR.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

This retrospective cohort study included 190 patients with idiopathic IgA nephropathy diagnosed by kidney biopsy between 1988 and 2005. The patients had GFR≥80 ml/min per 1.73 m2 at the time of diagnosis, and they had a paraffin-embedded kidney biopsy with eight glomeruli available.

RESULTS

In total, 170 (89%) and 20 (11%) patients were >18 and <18 years old, respectively; median (interquartile range) follow-up was 15 (12-22) years. Mesangial C4d deposit prevalence was 20% (38 of 190). At diagnosis, C4d-positive versus -negative patients had higher protein-to-creatinine ratio (median [interquartile range]: 1.94 g/g [0.9-3.1] versus 1.45 g/g [0.9-2.2]; P=0.04). During follow-up, C4d-positive patients showed a higher number of nephritic flares (median [range]: 1.4 [0-5] versus 0.9 [0-2]; P=0.04), had a higher protein-to-creatinine ratio (median [interquartile range]: 1.32 g/g [0.7-1.7] versus 0.89 g/g [0.1-1.3]; P<0.01), were more prone to receive repeated treatment with corticosteroids (45% versus 24%; P<0.01), and showed a larger reduction in eGFR (-1.6 versus -0.8 ml/min per 1.73 m2 per year; P=0.04). Furthermore, the presence of mesangial C4d deposits was an independent predictor of long-term kidney survival.

CONCLUSIONS

C4d deposits may be one of the earliest poor prognostic variables available for patients with idiopathic IgA nephropathy and normal kidney function at the time of diagnosis. However, Cd4 deposits alone are not associated with the response to angiotensin blockers or corticosteroid treatment.

Evaluation of a new condensed extra-corporeal circuit for cardiac surgery: a prospective randomized clinical pilot study

This prospective randomized clinical pilot study was conducted to evaluate a recently introduced reduced volume CPB system that is coated with the biopassive Xcoating™. Twenty-two patients undergoing coronary artery bypass grafting (CABG) with cardiopulmonary bypass (CPB), either with a fully heparin-coated CPB circuit (control, n=11) or with an Xcoating™ coated condensed extra-corporeal circuit (CondECC, n=11), were included.

We examined activation of the complement system (C3bc and C4bc), activation of neutrophils (BPI), the acute phase response (interleukin (IL)-6, and acute phase proteins (LBP, AGP, and CRP)), myocardial tissue injury (troponin T), hemolysis (free hemoglobin (FHb)), and clinical outcome parameters. Preoperative risk profiles were identical for both patient groups. All patients went through the procedure without major complications and were discharged from the hospital. FHb and BPI levels at the end of pump support ( p <0.01) and at 15 min after the administration of protamine ( p <0.05) were significantly higher in the control group. In addition, FHb levels were still significantly elevated upon arrival on the cardiothoracic intensive care unit (CICU) in the control group ( p <0.05). C3bc and C4bc, acute phase proteins, IL-6, and troponin T concentrations, and clinical outcome variables were identical in both patient groups.

In conclusion, the evaluated condensed extracorporeal circuit is a flexible and multifunctional CPB sytem that offers safe procedures. Furthermore, the results indicate improved biocompatibility of this option for extracorporeal circulation.

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.

Complement activation and effect of eculizumab in scleroderma renal crisis

BACKGROUND

Scleroderma renal crisis (SRC) is a life-threatening complication of systemic sclerosis characterized by abrupt onset of hypertension, thrombotic microangiopathy, and kidney injury. The mechanisms of the disease remain ill-defined, but a growing body of evidence suggests that activation of the complement system may be involved.

METHODS

Here, we report the case of a patient presenting with severe SRC and strong evidence of complement activation, both in serum and in the kidney, in the absence of genetic defect of the complement system.

RESULTS

Immunofluorescence studies on kidney biopsy showed significant deposits of C1q and C4d in the endothelium of renal arterioles, pointing toward activation of the classical pathway. Because of the dramatic clinical and histological severity, and the lack of response to early treatment with angiotensin-converting enzyme inhibitors, calcium channel blockers and plasma exchange, the patient was treated with the specific C5 blocker eculizumab.Contrarily to conventional treatment, eculizumab efficiently blocked C5b-9 deposition ex vivo and maintained hematological remission. Unfortunately, the patient died from heart failure a few weeks later. Postmortem examination of the heart showed diffuse patchy interstitial fibrosis, the typical lesion of systemic sclerosis-related cardiomyopathy, but normal coronary arteries and myocardial microvasculature.

CONCLUSION

SRC may lead to complement system activation through the classical pathway. Early administration of C5 inhibitor eculizumab may have therapeutic potential in patients with life-threatening SRC refractory to conventional treatment using angiotensin-converting enzyme inhibitors.

Complement Factor C4d Is a Common Denominator in Thrombotic Microangiopathy

Complement activation has a major role in thrombotic microangiopathy (TMA), a disorder that can occur in a variety of clinical conditions. Promising results of recent trials with terminal complement-inhibiting drugs call for biomarkers identifying patients who might benefit from this treatment. The primary aim of this study was to determine the prevalence and localization of complement factor C4d in kidneys of patients with TMA. The secondary aims were to determine which complement pathways lead to C4d deposition and to determine whether complement activation results in deposition of the terminal complement complex. We examined 42 renal sections with histologically confirmed TMA obtained from a heterogeneous patient group. Deposits of C4d, mannose-binding lectin, C1q, IgM, and C5b-9 were scored in the glomeruli, peritubular capillaries, and arterioles. Notably, C4d deposits were present in 88.1% of TMA cases, and the various clinical conditions had distinct staining patterns within the various compartments of the renal vasculature. Classical pathway activation was observed in 90.5% of TMA cases. C5b-9 deposits were present in 78.6% of TMA cases and in 39.6% of controls (n=53), but the staining pattern differed between cases and controls. In conclusion, C4d is a common finding in TMA, regardless of the underlying clinical condition. Moreover, C5b-9 was present in >75% of the TMA samples, suggesting that terminal complement inhibitors may have a beneficial effect in these patients. C4d and C5b-9 should be investigated as possible diagnostic biomarkers in the clinical work-up of patients suspected of having complement-mediated TMA.

Expression patterns of B cells in acute kidney transplant rejection

OBJECTIVES

To evaluate B-cell expression patterns and association with function and survival in dysfunctional kidney allografts.

MATERIALS AND METHODS

There were 110 kidney transplant recipients included who had for-cause biopsies. Demographic and transplant data were collected. Immunostaining for B cells, plasma cells, and C4d was performed by the immunoperoxidase technique in paraffin-embedded samples. Circulating antihuman leukocyte antigen donor-specific antibodies were detected in a single-antigen assay at biopsy. The main outcomes were kidney graft survival and function. The patients were evaluated in 3 groups according to the Banff classification: no rejection (40 patients), T-cell-mediated rejection (50 patients), and antibody-mediated rejection (20 patients).

RESULTS

The CD138-positive plasma cell-rich infiltrates predominated in antibody-mediated rejection and were associated with stronger reactivity against panel antibodies (r = 0.41; P ≤ .001) and positive donor-specific antibodies (r = 0.32; P ≤ .006). The CD20-positive lymphocytes were associated with T-cell-mediated rejection, increased human leukocyte antigen mismatch, and frequency of retransplant. The CD138-positive cell infiltrates also were significantly greater in patients who had late than early rejection. There was no correlation between cellular CD20 and CD138 expression, and neither CD20 nor CD138 predicted worse graft function or survival. Other markers of antibody-mediated rejection such as C4d and donor-specific antibodies were associated with worse graft function and survival at 4 years after transplant. In multivariate analysis, C4d was the only risk factor associated with graft loss.

CONCLUSIONS

After kidney transplant, CD20-positive B-cell infiltrates were associated with T-cell-mediated rejection, and CD138-positive plasma cells were associated with antibody-mediated rejection. Graft loss was associated with the presence of C4d.

Prognostic value of glomerular C4d staining in patients with IgA nephritis

INTRODUCTION

Mesangial IgA deposition is the initiative factor in the pathogenesis of IgA nephropathy (IgAN). Glomerular IgA depositon leads to activation local complement system. C4d positivity shows that complement activation occurs via alternative pathway. C4d positivity at the time of renal biopsy can be associated with poor prognosis in IgA nephropathy. We aimed to evaluate C4d deposition and renal outcome in patients with IgA nephritis.

METHODS

Between January 2005 and December 2009, 40 patients with IgA nephritis were enrolled. Renal biopsy specimens of 33 patients have been evaluated. C4d immunohistochemical staining was performed 3-μm deparaffinized and rehydrated sections of formaldehyde-fixed renal tissues, using rabbit polyclonal anti-human C4d as the antibody. Baseline demographical, clinical and laboratory data were recorded retrospectively.

RESULTS

Mean age of the patients was 35.9 ± 12.9 years and female/male ratio was 19/21. Mean duration of follow-up was 32.8 (12-60) months. Baseline glomerular filtration ratio (GFR) and proteinuria were 55.8 ml/min and 2.44 gr/day respectively at the time of renal biopsy. Eleven patients were C4d positive. Presence of hypertension (p=0.133), proteinuria (p=0.007), serum creatinine levels (p=0.056) and glomerulosclerosis (p=0.004), mesengial hypersellularity (p=0.0001) and interstitial fibrosis (p=0.006) at the time of renal biopsy were higher in C4d positive group rather than negative group. Evolution to renal failure were 63.6% in C4d positive group and 13.6% in negative group (p=0.006). Renal survival at 3 years was 39% in C4d-positive patients versus 66.7% in the C4d-negative patients (log rank- p=0.0072).

Re-examination of sinusoidal deposition of complement 4d in liver allografts: experience from a single institution

Complement 4d (C4d) is a marker of complement activation that has been used to evaluate humoral rejection in renal and heart allografts. Studies suggested a role for C4d detection in liver allografts in diagnosing acute cellular and humoral rejection but none correlated this with the pre-transplant liver disease. Our study analyzed the association of C4d deposition in liver allografts with the pre-transplant liver disease. C4d deposition was evaluated by indirect immunofluorescence and correlated with lymphocytotoxic crossmatch results, post-transplant clinicopathological diagnosis and type of pre-transplant liver disease. Allograft biopsies were classified by the native liver disease. After excluding 20 patients with rare liver diseases; C4d deposition was evaluated in 506 biopsies from 310 patients including 25 with PSC, 198 with viral hepatitis and 87 with other diseases. C4d immunereactivity distribution was not different among biopsies from patients with different lymphocytotoxic crossmatch results. Sinusoidal C4d deposition was noted in 11.9% of biopsies and 15.2% of patients (in one or more biopsies). 26% (9/35) of biopsies from patients with PSC had sinusoidal C4d deposition; more frequently than from patients with viral hepatitis 12% (43/348) (p=0.04) and other liver diseases 7% (8/123) (p=0.005). In conclusion, C4d deposition in liver allografts is independent of the crossmatch results. It occurs with a variety of pathologic abnormalities and underlying liver diseases; but is more frequent in patients with PSC. This suggests that mechanisms other than allo-immunity activate complement. The mechanisms and clinical significance of C4d deposition in liver allografts in patients with PSC remain to be determined.

Beyond Criteria and Definitions: Outcome of a Standardized Antibody-Mediated Rejection Protocol with a Diagnostic Schema Different from the Banff 2009 Criteria

A new clinical diagnostic schema is needed for the diagnosis of antibody-mediated rejection (AMR) in kidney transplant recipients due to the limited utility of C4d staining, lack of standardized quantitative tests for donor specific antibodies, and potential new diagnostic markers. The treatment of AMR remains controversial because previous studies included heterogeneous treatment modalities, small sample sizes, and short follow-up time. At the University of Michigan Transplant Center, 26 patients were diagnosed with AMR based on our diagnostic protocol including C4d-negative AMR in thesetting of graft dysfunction and Banff tissue injury type II (capillaritis) or type III (arteritis). After diagnosis, these patients received six sessions of plasmapheresis (PP) and IVIG (100 mg/kg after the first to fifth PP and 500 mg/kg with the last PP). Our novel finding in this analysis was the association between persistent C1q detection and graft loss. We confirmed that C4d positivity at diagnosis is associated with worse outcomes. Also, we found that response to our treatment protocol is dependent on C4d staining and Banff tissue injury type.

Glomerular and tubular C4d depositions in IgA nephropathy: relations with histopathology and with albuminuria

BACKGROUND

C4d has been used as an evaluation marker for antibody-mediated rejection for solid organ transplantation. Although some studies have proposed that complement activation is involved in renal diseases, very little information is available on pathogenesis. This study was conducted to investigate C4d deposition in IgA nephropathy and to find its relations with histopathology and albuminuria.

METHODS

This retrospective study included 23 patients who underwent renal biopsy at our medical center. The WHO grade of IgA nephropathy, interstitial inflammation and fibrosis, C4d staining and medical records including sex, age, and urine albumin were reviewed.

RESULTS

Thirteen patients (56.5%) were positive for C4d staining in the glomerulus and eleven patients (47.8%) were positive in the tubular epithelium. Glomerular C4d deposition was associated with albuminuria (p=0.044), and tubular C4d deposition was associated with a higher grade of IgA nephropathy (p=0.014).

CONCLUSIONS

Activation of the complement system was involved in renal damage and was identified through deposition of C4d in the glomerulus and tubules. Positive C4d staining in the glomerulus and the tubules may be associated with functional damage related to glomerular filtration and poor renal outcome.

Distinct patterns of C4d immunoreactivity in placentas with villitis of unknown etiology, cytomegaloviral placentitis, and infarct

C4d deposition is considered to be evidence of antibody-mediated rejection. This study was conducted to compare C4d immunoreactivity between villitis of unknown etiology (VUE) and cytomegaloviral placentitis. C4d immunohistochemistry was performed in cases with VUE (n = 16) and cytomegaloviral placentitis (n = 5). Distinct, linear C4d immunoreactivity along the syncytiotrophoblast was found in all VUE cases. In cytomegaloviral placentitis, the intensity of C4d immunoreactivity along the syncytiotrophoblast was not prominent, but cytoplasmic C4d immunoreactivity of villous cytotrophoblasts was frequently observed. Further screening of the cases with placental infarcts (n = 5) demonstrated prominent C4d immunoreactivity in the chorionic villi adjacent to the infarct. We report the characteristic co-localization of VUE and C4d immunoreactivity. The overall findings in this study strongly suggest that the complement activation is a common mechanism of diverse placental injuries associated with rejection, infection, and ischemia.

[Enzyme immunoassay of masked complement component C4 deficiency in patients with urogenital Chlamydia infection]

AIM

Development of new method of C4B isotype functional activity evaluation in enzyme immunoassay by using pharmaceutical preparation derinat as a classical pathway complement activator and its use for blood sera isotyping in confirmed urogenital tract chlamydia infection.

MATERIALS AND METHODS

Enzyme immunoassay was used to detect C4A and C4B isotype functional deficiency in blood sera of patients. Chlamydia etiology urogenital infection diagnosis was based on results of standard clinical-instrumental examination methods: vaginal clinical smear analysis, scrape sample light microscopy with consequent treatment by fluorescent monoclonal antibodies against Chlamydia trachomatis and PCR.

RESULTS

In acute form of the disease C4A deficiency frequency of occurrence was 0.36, and C4B deficiency - 0.55. In chronic form of the disease deficiency frequency of occurrence was 0.38 for both isotypes. In the group of healthy people isotype deficiency was 0.08 and 0.25, respectively.

CONCLUSION

Innate masked C4 deficiency interfere with the normal immune defense of organism against chlamydia infection, and antigen carbohydrate pathogenicity may possibly be more significant for the development of immune response to which C4B isotype activity is necessary.

Posttransplantation calcineurin inhibitor-induced hemolytic uremic syndrome: single-center experience

INTRODUCTION

Calcineurin inhibitor (CNI) induced HUS, although rare, can be a serious complication of renal transplantation. Classical syndrome of microangiopathic hemolytic anemia, thrombocytopenia, and acute renal injury may not be fully manifested.

METHODS

We retrospectively analyzed our data in 950 kidney recipients under follow-up in our center (1994-2008). We reviewed the kidney biopsies performed for these patients to exclude conflicting diagnoses like antibody mediated rejection.

RESULTS

HUS was diagnosed in 12 patients (1.26%). None of them had HUS as the original kidney disease. Cyclosporine was the primary immunosuppression in 9 and tacrolimus in 3 patients. The median day of onset was 7 days. Manifestations were anemia (100%), thrombocytopenia (75%), elevated reticulocyte count (62.5%), fragmented red blood cells (8.3%), elevated lactate dehydrogenase (LDH) enzyme (83.3%), increased fibrin degradation product (FDP) (83.3%), reduced haptoglobin level (42.9%) and hyperbilirubinemia (25%). CNI elimination was the first step in the management. Transfusion of fresh frozen plasma (FFP) was used in 10 patients and plasma exchange with FFP in the other two. All grafts recovered function. Cyclosporine or tacrolimus were reintroduction in two patients after complete clinical and laboratory recovery. Both patients developed recurrence of HUS. While the former did not the latter did recover on further treatment of HUS.

CONCLUSION

Anemia, thrombocytopenia, elevated LDH and FDP are the most frequent manifestations of HUS. Early CNI elimination and fresh plasma transfusion can revert CNI induced HUS and save the graft. Reintroduction of CNI may be deleterious to the graft and should be avoided.

Mechanisms of complement activation, C4d deposition, and their contribution to the pathogenesis of antibody-mediated rejection

Complement split products have emerged as useful markers of antibody-mediated rejection in solid organ transplants. One split product, C4d, is now widely accepted as a marker for antibody-mediated rejection in renal and cardiac allografts. This review summarizes the rationale for the use of C4d as a marker of antibody-mediated rejection, along with the clinical evidence supporting its use in the clinical diagnosis of antibody-mediated rejection. Antibody-independent mechanisms by which C4d can be activated by the classical and lectin pathways of complement activation are also identified. Finally, mechanisms by which complement activation stimulates effector cells (neutrophils, monocytes, macrophages, platelets, and B and T lymphocytes) as well as target cells (endothelial cells) are discussed in relation to antibody-mediated allograft rejection.

Specificity and sensitivity of screening for anti-HLA antibodies in kidney allograft dysfunction

BACKGROUND

Prospective testing for posttransplant circulating anti-HLA antibodies seems to be a critical noninvasive tool, but confirmatory data are lacking.

MATERIALS AND METHODS

Over the last 3 years, peritubular capillary (PTC) C4d deposition was prospectively sought by an immunofluorescence technique applied to frozen tissue in biopsies obtained for allograft dysfunction. Screening for circulating anti-HLA class I/II alloantibodies (AlloAb) by the flow cytometric test was performed simultaneously.

RESULTS

We evaluated 132 sets of biopsies and simultaneous serum samples. PTC C4d deposition was demonstrated in 15.9% (21/132) of biopsies. Circulating anti-HLA I/II AlloAb were detected in 25% (33/132) of serum samples. Employing receiver-operator characteristic (ROC) curves for all C4d-positive biopsies, screening for AlloAb showed a global specificity of 82% and sensitivity of 61.9%. When this analysis was restricted to biopsies obtained in the first month posttransplantation, the sensitivity increased to 81.8%, but the specificity decreased to 76.9%. After the first month posttransplantation, we observed sensitivity of 40.0% and a specificity of 86.4%. In the first month posttransplantation, all patients with a diagnosis of acute antibody-mediated rejection displayed circulating anti-HLA class I/II, but not always at the same time as the C4d-positive biopsy.

CONCLUSIONS

In the first month posttransplantation, prospective monitoring of anti-HLA antibodies may be useful. The high sensitivity allows the identification of patients at risk, affording an earlier diagnosis of antibody-mediated rejection. After the first month, the test can be used to evaluate allograft dysfunction episodes, since positivity is highly suggestive of an antibody-mediated process.

C4d-positive interacinar capillaries correlates with donor-specific antibody-mediated rejection in pancreas allografts

BACKGROUND

The deposition of the complement split fragment C4d and its association with acute antibody-mediated rejection (AMR) in pancreas transplant (PTx) is not well defined. To characterize the deposition of C4d in PTx, we analyzed 27 PTx biopsies from 18 patients transplanted between 2004 and 2007 at the University of Wisconsin.

METHODS

The presence of C4d was graded in interacinar capillaries (IAC), islets, interstitium, and small- and medium-size vessels. Sera obtained at the time or within 5 days of the biopsy were tested for antidonor-specific antibodies (DSA).

RESULTS

16 biopsies (59.26%) showed at least 5% C4d+ IAC (range 5%-90%). Of those, five biopsies (18.5%) revealed diffuse labeling (>50% C4d+ IAC) and 11 (40.74%) showed focal staining (5%-50% C4d+ IAC). C4d+ IAC (>5%) was significantly associated with the presence of strong DSA for class I or class II (P<0.018). C4d staining of the media or endothelium of small and medium-size vessels was a common finding in all biopsies without any association with DSA. Similarly, staining of islets and parenchymal interstitium was not statistically associated with AMR. The majority of patients received intravenous corticosteroid bolus and taper, with specific cases requiring thymoglobulin, IVIg, rituximab, or plasmapheresis. Forty-six percent of patients who demonstrated AMR returned to insulin therapy because of chronic graft damage and loss of C-peptide.

CONCLUSION

Our findings support the potential role of C4d labeling of PTx biopsies in the diagnosis of AMR and emphasize the staining of IAC as a valuable histologic tool for the diagnosis.

De novo collapsing glomerulopathy in a renal allograft recipient

Collapsing glomerulopathy (CG), characterized histologically by segmental/global glomerular capillary collapse, podocyte hypertrophy and hypercellularity and tubulo-interstitial injury; is characterized clinically by massive proteinuria and rapid progressive renal failure. CG is known to recur in renal allograft and rarely de novo. We report de novo CG 3 years post-transplant in a patient who received renal allograft from haplo-identical type donor.

Banff 07 classification of renal allograft pathology: updates and future directions

The 9th Banff Conference on Allograft Pathology was held in La Coruna, Spain on June 23-29, 2007. A total of 235 pathologists, clinicians and scientists met to address unsolved issues in transplantation and adapt the Banff schema for renal allograft rejection in response to emerging data and technologies. The outcome of the consensus discussions on renal pathology is provided in this article. Major updates from the 2007 Banff Conference were: inclusion of peritubular capillaritis grading, C4d scoring, interpretation of C4d deposition without morphological evidence of active rejection, application of the Banff criteria to zero-time and protocol biopsies and introduction of a new scoring for total interstitial inflammation (ti-score). In addition, emerging research data led to the establishment of collaborative working groups addressing issues like isolated 'v' lesion and incorporation of omics-technologies, paving the way for future combination of graft biopsy and molecular parameters within the Banff process.

[Chronic transplant nephropathy]

In 2007 there were important scientific contributions in the field of kidney transplant and specifically in chronic transplant nephropathy (interstitial fibrosis and tubular atrophy). A new nomenclature and classification of chronic kidney disease was probably the most important contribution in this entity. Use of the C4d stain has allowed the concepts of glomerulopathy to be updated and to reveal the frequency of this entity and its impact in kidney transplant. Finally, two experimental studies provide new perspectives on the treatment of chronic kidney disease such as the use of statins or the use of pyridoxamine to block glycation end products.

C4d fixing, luminex binding antibodies - a new tool for prediction of graft failure after heart transplantation

The standard method to detect pretransplant antibodies has been the complement dependent cytotoxicity (CDC) test of donor leukocytes. Solid phase assays to detect HLA antibodies in pretransplant serum reveal a greater number of sensitized patients, but their clinical impact is less certain. Here we have developed a method of detecting C4d fixing HLA antibodies on Luminex beads. Pretransplant serum from 565 cardiac transplant patients was retrospectively tested for the presence of HLA antibodies using CDC, HLA coated Luminex beads and C4d deposition on Luminex beads, and the results correlated with graft survival. Whereas 5/565 patients had CDC positive donor specific antibodies (DSA) before their transplant, this number was increased by 19 using Luminex beads. The 1-year survival of CDC -ve/Luminex +ve patients with DSA (n = 19) was 42% compared with 77% for CDC -ve/Luminex +ve without DSA (n = 39, p = 0.0039). Fixation of C4d (22/67 Luminex positive sera) had a negative effect on graft outcome; 1-year graft survival was, C4d +ve/DSA +ve (n = 11) 20%, C4d +ve/DSA -ve (n = 11) 91%, C4d -ve DSA +ve (n = 13) 54%, C4d -ve DSA -ve (n = 32) 75%, compared with 75% for antibody-negative patients (p = 0.0002). In conclusion, detection of Luminex +ve DSA in pretransplant serum provides a powerful negative predictor of graft survival, especially if they bind C4d.

Synergistic deposition of C4d by complement-activating and non-activating antibodies in cardiac transplants

The role of non-complement-activating alloantibodies in humoral graft rejection is unclear. We hypothesized that the non-complement-activating alloantibodies synergistically activate complement in combination with complement-activating antibodies. B10.A hearts were transplanted into immunoglobulin knock out (Ig-KO) mice reconstituted with monoclonal antibodies to MHC class I antigens. In allografts of unreconstituted Ig-KO recipients, no C4d was detected. Similarly, reconstitution with IgG1 or low dose IgG2b alloantibodies did not induce C4d deposition. However, mice administered with a low dose of IgG2b combined with IgG1 had heavy linear deposits of C4d on vascular endothelium. C4d deposits correlated with decreased graft survival. To replicate this synergy in vitro, mononuclear cells from B10.A mice were incubated with antibodies to MHC class I antigens followed by incubation in normal mouse serum. Flow cytometry revealed that both IgG2a and IgG2b synergized with IgG1 to deposit C4d. This synergy was significantly decreased in mouse serum deficient in mannose binding lectin (MBL) and in serum deficient in C1q. Reconstitution of MBL-A/C knock out (MBL-KO) serum with C1q-knock out (C1q-KO) serum reestablished the synergistic activity. This suggests a novel role for non-complement-activating alloantibodies and MBL in humoral rejection.

Acute antibody-mediated rejection of renal transplant: pathogenetic and diagnostic considerations

CONTEXT

Acute antibody-mediated rejection (AMR) has emerged recently as an important cause of graft failure.

OBJECTIVE

To review the pathogenetic, clinicopathologic, and diagnostic considerations of AMR.

DATA SOURCES

Review of literature and the authors' experience.

CONCLUSIONS

Acute antibody-mediated rejection is mediated by antibodies specific for donor antigens, which bind to target antigens and activate the complement system, culminating in tissue injury. The clinical manifestation of AMR is not specific, and transplant biopsy is needed for diagnosis. The glomeruli show thrombosis or neutrophils or mononuclear leukocytes in capillary lumens. The tubulointerstitial compartment shows edema, hemorrhage, necrosis, mild inflammation, and neutrophils or mononuclear leukocytes in the peritubular capillary lumens. The blood vessels show thrombosis, thrombotic microangiopathy, fibrinoid necrosis, or transmural vasculitis. Strong staining for C4d in the peritubular capillaries is characteristic. A definitive diagnosis of AMR requires (1) morphologic evidence of acute tissue injury, (2) immunopathologic evidence for antibody action, and (3) serologic evidence of circulating donor-specific antibodies. Acute antibody-mediated rejection should be suspected if some but not all 3 criteria are met. Since effective treatment is currently available, accurate and timely diagnosis of AMR is essential.

Diagnosis of acute humoral rejection using immunofluorescence in renal allograft biopsies- one step towards better understanding!

Immunofluorescence (IF) studies are important diagnostic tool in understanding pathogenesis involved in graft injury. Acute humoral rejection (AHR) associated with circulating donor-specific cytotoxic antibodies, is a poor prognosticator for graft survival. It can be diagnosed by staining for C4d antibody using indirect IF technique. C4d staining required to diagnose AHR was made mandatory for reporting renal allograft biopsies in 7th Banff conference. We present 2 years experience of IF studies using C4d polyclonal antibody on 546 renal allograft biopsies belonging to two groups of patients; 464 from group A (tolerance induction protocol) and 82 from group B (controls). We observed C4d focal positivity in 4 (0.9%) biopsies from group A and 4 (4.9%) from group B. We conclude that it is advisable to collect simultaneous core biopsy samples for IF studies and light microscopy to give better definition of allograft injury and thereby support in clinical management.

Activation of intrarenal complement system in mouse model for chronic cyclosporine nephrotoxicity

PURPOSE

Local activation of the complement system plays a role in target organ damage. The aim of our study was to investigate the influence of cyclosporine (CsA)- induced renal injury on the complement system in the kidney.

MATERIALS AND METHODS

Mice fed a low salt (0.01%) diet were treated with vehicle (VH, olive oil, 1 mL/kg/day) or CsA (30 mg/kg/day) for one or four weeks. Induction of chronic CsA nephrotoxicity was evaluated with renal function and histomorphology. Activation of the complement system was assessed through analysis of the expression of C3, C4d, and membrane attack complex (MAC), and the regulatory proteins, CD46 and CD55. CsA treatment induced renal dysfunction and typical morphology (tubulointerstitial inflammation and fibrosis) at four weeks.

RESULTS

CsA-induced renal injury was associated with increased the expression of C3, C4d, and MAC (C9 and upregulation of complement regulatory proteins (CD 46 and CD55). Immunohistochemistry revealed that the activated complement components were mainly confined to the injured tubulointerstitium.

CONCLUSION

CsA-induced renal injury is associated with activation of the intrarenal complement system.

Antibody-mediated renal allograft rejection: diagnosis and pathogenesis

Alloantibodies to HLA class I or II and other antigens expressed by endothelium cause a variety of effects on renal transplants, ranging from acute to chronic rejection, and even apparent graft acceptance (accommodation). Recognition of these conditions and appropriate therapy requires demonstration of C4d in biopsies, commonly confirmed by tests for circulating alloantibody. Substantial practical experience by pathologists in the interpretation and pitfalls of C4d stains are reviewed along with considerations of the clinical significance and pathologic mechanisms of the different effects of antibody on the endothelium of the renal allograft. Clinical trials will be needed to ascertain the optimal treatment for the newly appreciated conditions chronic humoral rejection and accommodation.

Subclinical acute antibody-mediated rejection in positive crossmatch renal allografts

Subclinical antibody-mediated rejection (AMR) has been described in renal allograft recipients with stable serum creatinine (SCr), however whether this leads to development of chronic allograft nephropathy (CAN) remains unknown. We retrospectively reviewed data from 83 patients who received HLA-incompatible renal allografts following desensitization to remove donor-specific antibodies (DSA). Ten patients had an allograft biopsy showing subclinical AMR [stable SCr, neutrophil margination in peritubular capillaries (PTC), diffuse PTC C4d, positive DSA] during the first year post-transplantation; 3 patients were treated with plasmapheresis and intravenous immunoglobulin. Three patients had a subsequent rise in SCr and an associated biopsy with AMR; 5 others showed diagnostic or possible subclinical AMR on a later protocol biopsy. One graft was lost, while remaining patients have normal or mildly elevated SCr 8-45 months post-transplantation. However, the mean increase in CAN score (cg + ci + ct + cv) from those biopsies showing subclinical AMR to follow-up biopsies 335 +/- 248 (SD) days later was significantly greater (3.5 +/- 2.5 versus 1.0 +/- 2.0, p = 0.01) than that in 24 recipients of HLA-incompatible grafts with no AMR over a similar interval (360 +/- 117 days), suggesting that subclinical AMR may contribute to development of CAN.

Significance of C4d deposition in the follicular lymphoma and MALT lymphoma and their relationship with follicular dendritic cells

We evaluated the deposition of C4d in follicular lymphomas (FL) and extranodal marginal zone B-cell lymphomas of mucosa-associated lymphoid tissue (MALT lymphoma). Deposition of C4d was detected in 118 lymphoma tissues from patients with lymphoma and in 20 reactive hyperplasia lymphadens (RHL) using immunohistochemistical methods. FL, MALT lymphoma, and RHL were studied using double staining for CD35/C4d and Bcl-2/C4d. We studied 26 FL tissues, 19 of which showed C4d deposition. C4d deposition was detected around the follicular dendritic cells (FDCs) in the neoplastic follicles. There was no significant difference between the positive ratio of C4d and the grades of FL. We studied 12 MALT lymphoma tissues, six of which displayed C4d deposition. In these tissues, C4d deposition was detected in the peripheral region of partially colonized follicles in the form of an irregular ring, but was not found in the central region. C4d deposition was negative in completely colonized follicles. There was no C4d deposition in diffuse large B-cell lymphomas, mantle cell lymphomas, B-small lymphocytic lymphomas, T-lymphoblastic lymphomas, peripheral T-cell lymphomas, and anaplastic large cell lymphomas. C4d around the FDCs in the neoplastic follicles was a specific indicator for FL. C4d deposition in partially colonized follicles of MALT lymphoma was completely different from that in neoplastic follicles of FL, forming a key point for differential diagnosis.

Characterization of CD4, CD8, CD56 positive lymphocytes and C4d deposits to distinguish acute cellular rejection from recurrent hepatitis C in post-liver transplant biopsies

INTRODUCTION

Hepatitis C viral (HCV) infection is the most common cause for liver transplantation (LTx) in USA. Hepatitis C viral recurrence in liver allograft is almost universal, which is often difficult to distinguish from acute cellular rejection (ACR).

AIM

Aim of the present study is to examine the differences between distribution of CD4, CD8, CD56 positive lymphocytes, and C4d deposits in patients with ACR and recurrent HCV.

PATIENTS AND METHODS

As a pilot project, a group of five post-LTx HCV RNA negative patients, strongly suspicious for ACR based on clinical findings and history of medication non-compliance and another group of five post-LTx HCV positive, medication compliant patients with abnormal liver function were retrospectively selected. Liver biopsies of these patients were stained with monoclonal CD4, CD8, CD56, and polyclonal C4d antibodies and compared.

RESULTS

Mean CD4, CD8, and CD56 counts in ACR group were 156.7 +/- 17.6, 35.4 +/- 8.8, and 1.0 +/- 1.8/HPF, respectively and were 89.7 +/- 41.3, 20.3 +/- 23.2, and 0.6 +/- 0.9/HPF, respectively in HCV recurrence group. Biopsies of four of five patients with ACR demonstrated moderate to strong C4d staining, whereas all patients with recurrent HCV had none to mild C4d staining.

CONCLUSION

Mean CD4, CD8, and CD56 were similar for acute rejection and recurrent HCV infection. However, 80% of patients with ACR showed moderate to strong staining for C4d and all recurrent HCV patients showed none to mild C4d staining.

Cutaneous vascular deposition of C5b-9 and its role as a diagnostic adjunct in the setting of diabetes mellitus and porphyria cutanea tarda

BACKGROUND

The cutaneous lesions of diabetes mellitus (DM) and porphyria cutanea tarda (PCT) exhibit distinctive microvascular changes including basement membrane zone thickening and lamellation, morphologically appearing as hyaline-like alterations of the vessel wall. Immunofluorescence demonstrates homogeneous mantles of immunoglobulin in the microvasculature. The staining intensity is variable and in some cases can closely approximate those immunofluorescent changes seen in photoaged skin.

OBJECTIVE

The purpose of this study was to establish an association between the microvascular changes seen in the skin from patients with DM and PCT and the presence of C5b-9 deposition, potentially defining the C5b-9 assay as an additional diagnostic adjunct.

METHODS

Routine light microscopy and immunofluorescence studies were conducted on skin biopsy specimens from 14 patients with cutaneous manifestations of DM and 17 patients with PCT. The immunofluorescence profile included IgG, IgM, IgA, C3, C3d, C4d, and C5b-9.

RESULTS

Fourteen of 14 DM and 17 of 17 PCT skin biopsy specimens revealed extensive granular and homogeneous vascular deposition of C5b-9; a similar pattern was observed for C3d and C4d. Control specimens from patients without DM and PCT, where C5b-9 was not an expected immunoreactant, were negative. Positive controls were cases of vasculitis, scleroderma, and dermatomyositis without DM and PCT where C5b-9 deposition was expected. C5b-9 deposition was observed and was of lesser magnitude than that encountered in patients with PCT or DM.

LIMITATIONS

We were unable to obtain detailed clinical information on some of the diabetic patients in regards to significant extracutaneous vascular complications. In addition, a correlation between hemoglobin 1 Ac levels and the extent of C5b-9 deposition could not be ascertained as the serum levels for hemoglobin 1 Ac were unknown.

CONCLUSION

Granular and homogeneous deposits of C5b-9 in vessels, along with homogeneous deposits of immunoglobulin within the blood vessels, are characteristic immunofluorescence findings in patients with DM and PCT. In regards to potential mechanisms of C5b-9 deposition, decreased metabolism of C5b-9 due to glycosylation of CD59 in the setting of DM and activation of complement by irradiated porphyrins in PCT are proposed. The extent of C5b-9 deposition suggests that this complex may play a pathogenetic role in the evolution of microvascular injury in patients with DM and PCT.

Immunoadsorption in severe C4d-positive acute kidney allograft rejection: a randomized controlled trial

Antibody-mediated rejection (AMR) frequently causes refractory graft dysfunction. This randomized controlled trial was designed to evaluate whether immunoadsorption (IA) is effective in the treatment of severe C4d-positive AMR. Ten out of 756 kidney allograft recipients were included. Patients were randomly assigned to IA with protein A (N = 5) or no such treatment (N = 5) with the option of IA rescue after 3 weeks. Enrolled recipients were subjected to tacrolimus conversion and, if indicated, 'anti-cellular' treatment. All IA-treated patients responded to treatment. One death unrelated to IA occurred after successful reversal of rejection. Four control subjects remained dialysis-dependent. With the exception of one patient who developed graft necrosis, non-responders were subjected to rescue IA, however, without success. Because of a high graft loss rate in the control group the study was terminated after a first interim analysis. Even though limited by small patient numbers, this trial suggests efficiency of IA in reversing severe AMR.

C4d: a marker for hepatic transplant rejection

BACKGROUND

Acute rejection is still a common complication of hepatic transplantation. The diagnosis, based on the histological examination of the graft, may be difficult to confirm in the setting of combined hepatitis C virus infection. The presence of C4d in the portal capillaries could facilitate differentiation between acute rejection and relapsed hepatitis C. The deposit of C4d provides evidence of activation of humoral immunity. To attempt to confirm this hypothesis, we searched for the presence of C4d in posttransplant hepatic biopsies.

METHODS

Thirty-six biopsies from 34 patients were analyzed retrospectively. The samples had been requested for one of the following reasons: suspected rejection, relapsed hepatitis C infection, or systematic check-up 1 year after the transplant.

RESULTS

C4d expression was common in biopsies classified as acute rejection (33%) and chronic rejection (100%). C4d was never detected in the event of recurrent hepatitis C infection without rejection.

CONCLUSION

These results, which are comparable to recently published data, give credence to the theory that C4d could be used as a marker for rejection following hepatic transplantation.

The Presence of B-Cell Nodules Does Not Necessarily Portend a Less Favorable Outcome to Therapy in Patients With Acute Cellular Rejection of a Renal Allograft

The presence of B-cell nodules in kidney biopsies of patients undergoing acute renal allograft rejection has been reported to be associated with glucocorticoid resistance and a high risk of graft failure. In an attempt to corroborate this observation, biopsies of renal transplants that evidenced Banff grade I A acute rejection were examined for the presence of B- or T-cell nodules, the detection of which was correlated with the therapeutic response. Biopsies from 14 consecutive renal transplant recipients with a diagnosis of acute cellular rejection were examined for the presence of T (CD3-positive) or B (CD20-positive) cells by immunohistochemistry. All patients were biopsied because of a rise in serum creatinine. No biopsy showed evidence of acute humoral rejection. Immunofluorescence microscopy was negative for C4d deposition in peritubular capillaries. There were no neutrophils in the peritubular or glomerular capillaries. Five patients had T-cell nodules; four had B-cell nodules; three had both T- and B-cell nodules; two had no nodules. All biopsies contained CD3-positive cells in the tubules and in the interstitium. In all but one of the patients, episodes of acute rejection were treated with steroids (one received thymoglobulin). Furthermore two patients received mycophenolate mofetil and one, sirolimus. There were no significant differences among the groups in either the initial creatinine or the creatinine after therapy. The presence of B-cell nodules in renal allograft biopsies of patients experiencing acute cellular rejection did not portend a less favorable outcome.

Rescue Therapy by Immunoadsorption in Combination With Tacrolimus and Mycophenolate Mofetil for C4d-Positive Acute Humoral Renal Allograft Rejection

The aim of this study was to investigate the efficacy of immunoadsorption (IA) in combination with tacrolimus (TAC; 0.14 to 0.16 mg/kg/d) and mycophenolate mofetil (MMF; 1.5 to 2.0 g/d) rescue therapy for C4d-positive acute humoral rejection in nine cadaveric renal allograft recipients. Initial Panel reactive antibody (PRA-I and PRA-II levels were as high as 28.8% +/- 16.2% and 15.3% +/- 8.9%, IA therapy significantly decreased PRA-I and PRA-II levels to 5.9% +/- 2.9% and 2.2% +/- 0.6%, respectively. Total serum immunoglobulin levels were markedly decreased. Repeated allograft renal biopsy in nine patients revealed remission of acute humoral rejection (AHR), and the deposition of C4d disappeared and reduced. With a mean follow-up of 29.4 +/- 5.4 months, patient and allograft survivals were 100%, and renal function remained stable with a mean serum creatinine of 1.1 +/- 0.3 mg/dL. Our findings suggested that a therapeutic approach combining IA and TAC and MMF rescue improved the outcomes of AHR.

C4d deposits mark sites of meniscal tissue disintegration

Although the frequent occurrence of meniscal degeneration is a well-known fact and its consequences include rupture and even loss of the meniscus, the pathogenetic factors are established insufficiently. Because complement factors and leukocytes are present in synovial fluid, we tried to detect complement deposits and macrophages in menisci, which displayed degenerative changes. We therefore performed a retrospective analysis by immunohistochemical staining of C4d and CD68 in meniscal tissue derived from patients (n=15) who underwent meniscectomy because of meniscal tears and from three autopsy cases (n=3). In this study, focal C4d deposits in the meniscal extracellular matrix in areas of mucoid degeneration or fibrillation were demonstrated for the first time, while no C4d deposits in the avascular zone of menisci without signs of degeneration or injury could be detected. In addition, colocalization of C4d and CD68+ cells was found at sites of meniscal tissue disintegration in five cases. These results represent the first evidence for an involvement of complement and macrophages in meniscal tissue disintegration, indicating a complement mediated reaction at the site of tissue alteration.

Acute humoral rejection and C4d immunostaining in ABO blood type-incompatible liver transplantation

Complement C4d deposition in graft capillaries has been reported to be associated with antibody-mediated rejection in kidney and other solid organ transplantation. The correlation of C4d deposits and humoral rejection in liver transplants, however, is not well understood. We investigated the C4d immunostaining pattern in 34 patients whose liver biopsy was taken within the first 3 postoperative weeks for suspected acute rejection after ABO blood type-incompatible liver transplantation. The staining pattern was classified as positive (portal stromal staining), indeterminate (endothelial staining only), and negative (no staining). Positive C4d immunostaining was seen in 17 (50%) patients and was significantly associated with high (x64 or more) postoperative antidonor A/B antibody (immunoglobulin M (IgM)) titers (88 vs. 35%, P = 0.002) and poorer overall survival rate (41 vs. 88%, P = 0.007). Ten of 11 (91%) cases with histological acute humoral rejection (periportal edema and necrosis (PEN) or portal hemorrhagic edema) were positive for C4d, all of which showed high postoperative antibody titers. The other histologies associated with C4d positivity was purulent cholangitis (n = 4), coagulative hepatocyte necrosis (n = 1), acute cellular rejection (n = 1), and hepatocanalicular cholestasis (n = 1). Full clinical recovery was observed in only 6 of 17 (35%) C4d-positive patients, and tended to be associated with a lower rejection activity index (RAI). In conclusion, our study indicates that C4d deposits in the portal stroma can be a hallmark of acute humoral rejection in ABO-incompatible liver transplantation, and allograft damage can be reversible in a minority of cases.

Diagnostic value of C4d in renal allograft biopsies in different clinical settings: absence of C4d in grafts from non-heart-beating donors

Humoral mechanisms of rejection after kidney transplantation (TX) can be identified through the detection of diffuse complement C4d deposits in peritubular capillaries (PTC) in graft biopsies or donor-specific antibodies (DSA) in serum samples. It has been hypothesized that ischemic injury in the graft may facilitate humoral responses. Kidney grafts from non-heart-beating donors (NHBD) present more often severe ischemia lesions than grafts from heart-beating or living donors.

METHODS

We reviewed kidney TX biopsies performed from May 2002 to November 2004 with special interest paid to recipients from NHBD. We checked corresponding frozen tissue for the detection of C4d in PTC using immunofluorescence with a monoclonal antibody against C4d. We also collected post-TX contemporaneous DSA data, either flow crossmatches or cytotoxic PRA.

RESULTS

During this period, we performed 22 kidney TXs from NHBD of a total of 326 kidney TX (either single or combined with other grafts). Nine patients of this group underwent 12 biopsies for delayed graft function over 15 days or deteriorating scans. All biopsies showed acute tubular necrosis, but one also presented IA Banff acute rejection and another one had neutrophils in PTC. Frozen tissue from these 12 biopsies did not have diffuse C4d deposits in PTC. Serum samples of seven of nine patients were available: four had negative DSA flow crossmatches and three had 0% PRA within the same period. We diagnosed acute humoral rejection (AHR) in 13 patients-with acute renal dysfunction, C4d in biopsies and DSA after kidney TX-of 38 with high clinical suspicion for AHR. We detected C4d in seven biopsies of 30 patients performed more than 6 months after TX.

CONCLUSIONS

Severe ischemic injury does not necessarily determine the activation of humoral mechanisms of rejection mediated through DSA. Therefore, C4d is extremely interesting for the identification of humoral rejection in any clinical setting after kidney TX.

Focal peritubular capillary C4d deposition in acute rejection

BACKGROUND

Diffuse peritubular capillary (PTC) C4d deposition has been shown to be associated with relatively poor graft outcome. The significance of focal PTC C4d staining in the early post-transplant period is uncertain.

METHODS

Sixty-five biopsies from 53 patients with acute rejection were graded (Banff '97 criteria), stained for C4d, monocytes and T cells, and divided into three groups according to PTC C4d: (i) focal C4d (F) (14 biopsies, 14 patients), (ii) diffuse C4d (D) (23 biopsies, 15 patients) and (iii) no C4d (N) (28 biopsies, 24 patients). The three groups were compared with respect to a variety of biopsy and clinical parameters including outcome.

RESULTS

The incidence of transplant glomerulitis and glomerular monocyte infiltration were significantly greater in F (64% and 2.0+/-2.0) and D (57% and 3.4+/-2.0) than in N (11% and 0.2+/-0.2). A significantly higher proportion of F (93%) demonstrated acute cellular rejection (Banff '97 grade > or = 1A) than did D (35%). The F and D groups included significantly more females (50 and 67%, respectively) than did N (21%). The percentage of patients with a second or third transplant was higher in F (29%) and D (40%) than in N (8%) (P = 0.0589). The proportion of patients with glomerular filtration rate < 30 ml/min at 12, 24 and 48 months was higher in the D and F groups than in the N, and there was a statistically significant increasing trend in odds of this outcome occurring at 48 months across the three groups (D > F > N group) (P = 0.0416).

CONCLUSION

The results suggest that the biopsy findings and clinical course in patients with focal PTC C4d staining are similar to those associated with diffuse C4d.

Graft loss associated with late humoral rejection after renal transplantation

Antibody-mediated rejection (AMR) is an important cause of renal allograft loss after renal transplantation. With the improvement of the crossmatching method and the use of more aggressive immunosuppressants, the incidence and outcome of early AMR has been reduced. Late humoral rejection is becoming an important cause of graft loss. In this chapter, we demonstrated 8 renal allograft recipients who experienced renal allograft dysfunction associated with late humoral rejection, which suggests that graft loss could be caused by anti-donor antibodies.

C4d-positive renal transplants: single-center clinical outcomes

Among 269 biopsies performed in our institution in 2006, 24 biopsies were C4d positive. There were seven cases of early AMR (< 6 months post-transplant) and 17 cases of late AMR. Cellular rejection was found in 12 biopsies (50%) and classified as type I tubulointerstitial (six biopsies: five Banff IA and one Banff IB) and type II vascular (six biopsies: Banff IIA); in five biopsies (21%), borderline rejection was diagnosed. Changes consistent with chronic rejection were found in six biopsies (25% of all and 35% of biopsies in the late post-transplant period). Among patients with early-onset AMR, there were three cases with thrombotic microangiopathy. Graft function improved in all cases of early AMR after treatment with steroid pulses, and in two cases it improved with ATG and increasing doses of MMF, respectively. All of these patients showed good graft function during follow-up. Methylprednisolone pulses with various modifications of immunosuppressive protocols were used for treatment of late-onset AMR with rather poor effect. Graft function improved in only five patients (29%) but decreased thereafter in three cases; dialysis was started in four cases (24%), and one patient died in sepsis. AMR could be associated with various histological features; trombotic microangiopathy was the specific type of injury for the early-onset AMR in our study, and all but one late-onset AMR were associated with chronic changes. Conventional treatment of acute rejection with steroid pulses or ATG was effective in cases of AMR diagnosed early after transplantation but was of little benefit in cases during the late post-transplant period. Treatment with plasmapheresis with or without immunologlobins or rituximab could be the best therapy in such cases.

C4d Complement Split Product in Diagnosis of Immunological Activity of Chronic Allograft Nephropathy

INTRODUCTION

Activation of the humoral branch of the immunological response is currently believed to play an important role in pathogenesis of chronic allograft nephropathy. The impact of humoral alloreactivity, indicated by the presence of C4d deposits in peritubular capillaries of a renal allograft, on the development of chronic allograft nephropathy is a significant problem in transplantation. The aim of the study was to assess and correlate C4d expression in patients with chronic allograft nephropathy, with clinical and morphological variables, as well as to assess the impact of a change in immunosuppression regimen on posttransplant course and renal allograft morphology.

PATIENTS AND METHODS

Twenty-six patients with chronic allograft nephropathy underwent biopsies to correlate C4d expression with clinical parameters and morphological findings. In all patients azathioprine was replaced with mycophenolate mofetil with additional CsA dose reduction in 12 patients. After 1 year, 14 protocol biopsies were performed.

RESULTS

The frequency of C4d peritubular capillary deposition among patients with chronic allograft nephropathy was 30%. C4d expression appeared later after transplantation, was correlated with chronic allograft glomerulopathy and proteinuria but not other clinical or histological variables. C4d deposits displayed no independent impact on serum creatinine level. Proteinuria was significantly more reduced in the C4d(+) group. Progression of chronic morphological changes was significantly accelerated in the C4d(+) group.

CONCLUSION

C4d peritubular capillary expression did not differentiate patients after immunosuppression enhancement, but it predisposed to progression of chronic morphological findings during 1-year observation.

C4d deposition in lung allografts is associated with circulating anti-HLA alloantibody

The complement activation demonstrated by vascular C4d deposition is used to diagnose antibody-mediated rejection (AMR) in renal allografts, but remains controversial in lung transplantation (LTX).

METHODS

C4d deposition was assessed by immunohistochemistry in 192 lung transplant biopsies from 32 patients. ELISA analysis was performed on 415 serum samples in those 32 temporally and rejection-grade matched LTX patients; 16 patients developed HLA-Ab, while the other 16 patients remained negative. The specificity of C4d staining was further compared in 18 additional LTX patients without HLA-Ab or acute cellular rejection (ACR), but in the presence of CMV-pneumonitis or reperfusion injury.

RESULTS

Specific subendothelial C4d deposition was seen in 5 of 16 (31%) patients with HLA-Ab and was absent in 16 patients without HLA-Ab (p<0.05). All patients with specific C4d deposition exhibited donor-specific HLA-Ab. There were 13 patients with bronchiolitis obliterans syndrome in the group of 16 HLA-Ab positive patients, versus 2/16 in ELISA-negative patients (p<0.005). One of 7 patients with CMV pneumonitis and 2 of 11 patients with reperfusion injury also showed C4d positivity (not statistically significant).

CONCLUSIONS

In this study, specific subendothelial C4d deposition was a marker for the involvement of HLA-Ab in lung allograft rejection. The patchy nature, low sensitivity, and specificity of C4d staining might limit clinical use in protocol biopsies. However, in patients with decreasing pulmonary function, refractory ACR and/or HLA-Ab, specific C4d deposition may serve as a marker of coexistent AMR.