Marker Of Antibody-mediated Rejection Research Articles

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Antibody mediated rejection (AMR) is a significant source of morbidity and mortality in cardiac transplant recipients. Because antibody mediated rejection is known to use the complement pathway, assessment of antibodies that fix complement, such as C1q may show promise here as a quantitative marker of the degree of severity of disease, as well as response to treatment. This was a retrospective case study of 5 patients with biopsy proven AMR. Charts were analyzed for rejection episodes, echocardiographic data, and treatment for AMR. AMR was determined from C4d and CD68 stained sections. Final clinical diagnosis included evidence of allograft dysfunction, HLA donor specific antibody (DSA) and C1q DSA. The 5 cases are graphically presented with time points for biopsy evaluation, echocardiogram, HLA and C1q antibody testing, and treatment. The results of this study indicate that measuring donor specific C1q antibodies may be useful in assessing the severity of AMR as well as the response to treatment. Evaluation of these cases indicate pursuing a larger study is a worthwhile endeavor to further investigate the role of C1q testing as an independent and quantifiable marker for AMR. C1q antibody evaluation may help reduce the frequency of routine surveillance biopsy in cardiac transplant patients, leading to a less invasive method of assessing for rejection. In addition, it can be used to appropriately guide treatment. Studies with longer-term follow-up may help to determine how long after treatment the antibodies will take to completely clear, as more information is needed on how to properly interpret elevated levels of C1q antibodies post-treatment. Correlation of post-treatment levels of C1q with the clinical status of the patient, as well as biopsy data, will help to determine if measurement of C1q can help determine if a particular treatment was a success or a failure. Overall, this study is a good starting point for the assessment of C1q HLA DSA as a marker for AMR.

Role of complement and NK cells in antibody mediated rejection

Despite extensive research on T cells and potent immunosuppressive regimens that target cellular mediated rejection, few regimens have been proved to be effective on antibody-mediated rejection (AMR), particularly in the chronic setting. C4d deposition in the graft has been proved to be a useful marker for AMR; however, there is an imperfect association between C4d and AMR. While complement has been considered as the main player in acute AMR, the effector mechanisms in chronic AMR are still debated. Recent studies support the role of NK cells and direct effects of antibody on endothelium cells in a mechanism suggesting the presence of a complement-independent pathway. Here, we review the history, currently available systems and progress in experimental animal research. Although there are consistent findings from human and animal research, transposing the experimental results from rodent to human has been hampered by the differences in endothelial functions between species. We briefly describe the findings from patients and compare them with results from animals, to propose a combined perspective.

Re-examination of the Lymphocytotoxic Crossmatch in Liver Transplantation: Can C4d Stains Help in Monitoring?

C4d-assisted recognition of antibody-mediated rejection (AMR) in formalin-fixed paraffin-embedded tissues (FFPE) from donor-specific antibody-positive (DSA+) renal allograft recipients prompted study of DSA+ liver allograft recipients as measured by lymphocytotoxic crossmatch (XM) and/or Luminex. XM results did not influence patient or allograft survival, or cellular rejection rates, but XM+ recipients received significantly more prophylactic steroids. Endothelial C4d staining strongly correlates with XM+ (<3 weeks posttransplantation) and DSA+ status and cellular rejection, but not with worse Banff grading or treatment response. Diffuse C4d staining, XM+, DSA+ and ABO- incompatibility status, histopathology and clinical-serologic profile helped establish an isolated AMR diagnosis in 5 of 100 (5%) XM+ and one ABO-incompatible, recipients. C4d staining later after transplantation was associated with rejection and nonrejection-related causes of allograft dysfunction in DSA- and DSA+ recipients, some of whom had good outcomes without additional therapy. Liver allograft FFPE C4d staining: (a) can help classify liver allograft dysfunction; (b) substantiates antibody contribution to rejection; (c) probably represents nonalloantibody insults and/or complete absorption in DSA- recipients and (d) alone, is an imperfect AMR marker needing correlation with routine histopathology, clinical and serologic profiles. Further study in late biopsies and other tissue markers of liver AMR with simultaneous DSA measurements are needed.

Clinical and pathological correlations of C4d immunostaining and its infl uence on the outcome of kidney transplant recipients

C4d is a marker of antibody-mediated rejection (ABMR) in kidney allografts, although cellular rejection also have C4d deposits. To correlate C4d expression with clinico-pathological parameters and graft outcomes at three years. One hundred forty six renal transplantation recipients with graft biopsies by indication were included. C4d staining was performed by paraffin-immunohistochemistry. Graft function and survival were measured, and predictive variables of the outcome were determined by multivariate Cox regression. C4d staining was detected in 48 (31%) biopsies, of which 23 (14.7%) had diffuse and 25 (16%) focal distribution. Pre-transplantation panel reactive antibodies (%PRA) class I and II were significantly higher in C4d positive patients as compared to those C4d negative. Both glomerulitis and pericapillaritis were associated to C4d (p = 0.002 and p < 0.001, respectively). The presence of C4d in biopsies diagnosed as no rejection (NR), acute cellular rejection (ACR) or interstitial fibrosis/ tubular atrophy (IF/TA) did not impact graft function or survival. Compared to NR, ACR and IF/TA C4d⁻, patients with ABMR C4d⁺ had the worst graft survival over 3 years (p = 0.034), but there was no difference between ABMR versus NR, ACR and IF/TA that were C4d positive (p = 0.10). In Cox regression, graft function at biopsy and high %PRA levels were predictors of graft loss. This study confirmed that C4d staining in kidney graft biopsies is a clinically useful marker of ABMR, with well defined clinical and pathological correlations. The impact of C4d deposition in other histologic diagnoses deserves further investigation.

Complement component 4d immunostaining in liver allografts of patients with de novo immune hepatitis

De novo immune hepatitis (DNIH) is a form of late graft dysfunction after liver transplantation. The fine mechanisms leading to the development of DNIH are not known, and whether this hepatitis is a form of rejection or a result of an auto/alloimmune injury has not been established. In our patients, DNIH was always preceded by the production of donor-specific antibodies against the glutathione S-transferase T1 (GSTT1) enzyme because of a genetic mismatch in which the donors carried the wild-type gene and the recipients displayed the null genotype. Complement component 4d (C4d) immunopositivity in 12 paraffin-embedded liver biopsy samples from 8 patients diagnosed with DNIH associated with anti-GSTT1 antibodies was retrospectively evaluated. Six patients with a diagnosis of chronic rejection (CR) and 7 patients with hepatitis C virus recurrence were included as control groups. Among the patients with DNIH, 7 showed C4d-positive immunostaining localized in the portal tracts, whereas in the tested biopsy samples of the 2 control groups, this staining pattern was absent. Four biopsy samples of the CR group showed C4d-positive sinusoidal staining. This study confirms the activation of the complement pathway in the presence of donor-specific antibodies, which was shown by the deposition of C4d elements in liver biopsy samples of patients with DNIH. The use of C4d as a marker of antibody-mediated rejection in liver allografts in the presence of antidonor antibodies is discussed, and it may contribute to improved differential diagnoses based on biopsy findings.

Transplantomics and Biomarkers in Organ Transplantation: A Report From the First International Conference

Transplantomics and Biomarkers in Organ Transplantation: A Report From the First International Conference

Diagnosis of antibody-mediated rejection in cardiac transplantation: a call for standardization

Currently clinical antibody-mediated rejection (AMR) requires demonstration of histopathologic changes, presence of donor-specific allo-antibodies and allograft dysfunction to establish the diagnosis. Pathology practice patterns in the immunopathologic evaluation and interpretation of cardiac transplant biopsies vary. Specific recommendations for post-transplant allo-antibody monitoring are lacking. Recently, the occurrence of surveillance biopsies being positive for immunopathologic markers of AMR without concomitant graft dysfunction is increasingly recognized. This review focuses on issues of standardization in the diagnosis of AMR and the need for updated criteria. Concomitant use of C4d and C3d proved to be strongly predictive of the presence of circulating allo-antibodies and allograft dysfunction in heart transplant recipients. Asymptomatic patients with histopathologic evidence of AMR in their biopsies appear to have increased risk for cardiac allograft vasculopathy and cardiovascular mortality. The role of nonhuman leukocyte antigen antibodies in AMR has not been adequately addressed. A consensus on the frequency of AMR screening, antibody panels, interpretation and reporting of stains will enhance standardization of the diagnosis of AMR. Further studies are needed to define asymptomatic or subclinical AMR and to determine the long-term outcome of pathologic evidence of complement activation without allograft dysfunction.

C4d Binding Correlated With Strong HLA Antibodies Involved in Graft Failures

Capillary C4d was an established marker of antibody-mediated rejection in kidney transplantation. Recently, C4d fixation to antibodies against HLA-coated beads were found to be a novel way to test for complement-fixing antibodies in the serum. To find differences between complement-fixing and nonfixing antibody assays, we tested HLA antibodies and C4d in 102 sera of graft-failure patients using the LABScreen and FlowPRA bead methods. HLA antibodies were observed in the sera of patients who subsequently failed and who continued to function. C4d fixing antibodies were present in the sera of patients who subsequently experienced graft failures and those with high fluorescence intensity of HLA antibodies by FlowPRA. In antibody dilution studies with LABScreen, we noted that C4d fixation occurred only at high antibody titers, and fluorescence was lost as sera were diluted. In conclusion, the fluorescence levels of antibodies were more important that the C4d content. Quantitative aspects of antibody testing using the fluorescence value appears to be a valuable factor when examining anti-HLA antibodies posttransplantation.

Deposition of C4d and C3d in cardiac transplants: A factor in the development of coronary artery vasculopathy

Coronary artery vasculopathy (CAV) is the major life-limiting factor in cardiac transplantation, after 1 year. Antibody-mediated rejection (AMR) has been associated with development of both acute and chronic rejection. We analyzed endomyocardial biopsies for pathologic markers of AMR (C4d and C3d), from the first 2 years post-transplantation, to determine complement deposition in relation to the development of CAV. A retrospective, matched-pair study was used. Group 1 subjects (n = 26) were CAV-negative at 8 years, and Group 2 (n = 26) had angiographically detectable CAV at 4 years. Biopsies from six time-points were studied (total = 282). Immunohistochemistry was performed for C4d, C3d and CD68. Biopsies were graded for rejection using ISHLT criteria. Although CAV was not significantly associated with C4d deposition, it was associated with C3d deposition (p = 0.043). Only 4% of C4d and 5% of C3d biopsies were completely negative. Group 1 had 6 AMR-positive biopsies, with Group 2 having 8. There was no significant relationship between acute cellular rejection or AMR events and CAV. This study demonstrates that complement deposition is a frequent occurrence in the first 2 years post-transplantation. Although acute rejection is a known risk factor for CAV, in this study the relationship was found not to be significant. No relationship was found with the development of CAV and histologic features of AMR, when assessed by C4d deposition alone. However, an association between C3d deposition and the development of CAV was determined in this study group, suggesting that complement activation may play a role in the pathogenesis of CAV.

94: Phosphoproteomic Analysis of Cardiac Allograft Biopsies Reveals Novel Markers of Antibody Mediated Rejection

94: Phosphoproteomic Analysis of Cardiac Allograft Biopsies Reveals Novel Markers of Antibody Mediated Rejection

Monocytes/macrophages in renal allograft rejection

Monocytes/macrophages (MO) have long been recognized to be involved in renal allograft rejection. Monocytes/macrophages have been detected in the glomerular, vascular, and tubulointerstitial compartments during rejection. The recent demonstration that peritubular capillary deposition of complement split factor C4d, a marker for antibody-mediated rejection, is associated with relatively marked MO infiltration of the allograft during acute rejection is a significant development in our understanding of the role of the MO in rejection. High levels of MO in rejecting allografts have been associated with severe rejection, and glomerular MO infiltration in particular has been shown to be an indicator of poor graft outcome.

Utility of Routine Immunofluorescence Staining for C4d in Cardiac Transplant Recipients

Immunofluorescence staining of endomyocardial biopsy (EMB) specimens to detect the complement fragment C4d is used to diagnose antibody-mediated rejection. However, data are limited regarding the utility of routine staining for C4d in clinical care. This study retrospectively reviewed the clinical course of adult cardiac transplant recipients who underwent > or = 2 EMBs with immunofluorescence C4d staining at the University of Texas Southwestern Medical Center since September 2006. C4d staining was performed by the immunohistochemistry laboratory and interpreted by the members of the surgical pathology department, in conjunction with interpretation of the routine hematoxylin and eosin staining. Donor-specific antibodies (DSA) were routinely assessed at the time of clinical rejection. Of 67 patients, specimens were positive for C4d (C4d+) in 14 and negative for C4d (C4d-) in 53. The frequency of acute cellular rejection (ACR) in these 2 groups was 57% (8 of 14, designated C4d+/ACR+) vs 11% (6 of 53, designated C4d-/ACR+; p < 0.001). Significantly more patients with a positive C4d specimen had a positive retrospective donor specific crossmatch, presence of DSA after transplantation, and depressed graft function (p < 0.01 for each). Positive C4d immunofluorescence staining on EMB specimens was associated with ACR, reduced allograft function, a positive retrospective crossmatch, and the presence of DSA after transplantation. The latter 2 observations support the contention that C4d deposition is a marker of antibody-mediated rejection. Routine evaluation of C4d staining is feasible in the clinical setting and may identify variable patterns of rejection.

Subclinical peritubular capillaritis in serial graft biopsies in cadaveric kidney transplant recipient with pre‐transplant anti‐HLA antibodies

National Fukuoka-Higashi Medical Center, Koga, Japan A 63-yr-old Japanese woman on 18-yr hemodialysis (HD) program underwent cadaveric kidney transplantation from non-heart beating donor. Pre-transplant lymphocytotoxicity test was negative, but flow cytometric cross-match and flow-cytometric panel reactive antibody (PRA) screening tests were positive. Flow-PRA single-antigen test revealed several anti-HLA antibodies including donor-specific antibody (DSA). She was treated with plasma exchange (PEX) and rituximab to prevent antibody-mediated rejection (AMR). Urinary output increased from post-operative day (POD) 5 and HD was discontinued from POD8. Graft biopsy performed on POD11 showed severe peritubular capillaritis (PTCitis), numerous polymorphonuclear neutrophils (PMNs), and moderate glomerulitis. Although C4d immunostaining on PTC was negative, the case was diagnosed as subclinical AMR based on the presence of pre-transplant DSA and PTCitis with predominant PMNs. The patient was treated with additional PEX and rituximab, which increased urinary output and reduced serum creatinine (sCr). Graft biopsy repeated on POD39 showed persistent severe PTCitis, moderate interstitial infiltration, and mild tubulitis. C4d on PTC was negative again. The patient was discharged from the hospital on POD40. During the seven months follow-up at the outpatient clinic, the sCr level has shown a slight increase. In this case, the patient had DSA, which can be detected only by flow-PRA. In both graft biopsies, C4d on PTC was negative despite the presence of severe PTCitis, and thus the diagnosis of AMR could not be established. However, the significance of subclinical PTCitis is reported perhaps as an early marker for chronic AMR and to emphasize the importance of close follow-up.

Antibody Responses in Immunosuppressed Organ Allograft Recipients - Brief Review of the Current Literature

With the rapidly growing application of new highly sensitive techniques for detection and definition of antibodies specific to HLA and non – HLA antigens, a significant number of studies have reported that de novo generation of antibodies after organ transplantation is associated with severe immunological complications and graft loss. The presence of donor specific complement – binding antibodies is confirmed by the finding of C4d deposits in the peritubular capillaries of the kidney graft – a method now regularly used as a marker of antibody-mediated rejection. The clinical significance of various techniques for antibody identification with respect to the incidence of organ transplant rejection is however still a matter of discussion. The discrepancies in the literature are most likely caused by variations in the approaches for antibody characterization and differences in patient cohorts and immunosuppressive protocols. In this concise review, we will discuss some recent developments in the study of the role of antibodies specific to HLA and non – HLA antigens for the occurrence of cellular and antibody-mediated rejection after organ transplantation. Keywords: Organ transplantation, antibodies, rejection, HLA, MICA, crossmatch

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.

Analysis of Different Staining Techniques for C4d Detection in Renal Allograft Biopsies

Capillary C4d deposition has been recognized as a marker of antibody-mediated rejection (AMR). Although the detection of capillary C4d by means of immunofluorescence (IF) in cryostat sections is well established, frozen tissue is not always available, thus limiting the diagnosis of AMR. The aim of the present study was to analyze different techniques for C4d staining and the prevalence of C4d in renal allograft biopsies. Detection of C4d was carried out using IF or immunohistochemistry (IHC) on frozen and paraffin sections of renal allograft biopsies available from the same patients. Biopsies obtained from 20 patients were classified into 3 groups: no rejection, acute rejection, and chronic allograft nephropathy (CAN). The capillary C4d deposition prevalence in frozen-IF, considered the gold standard technique for C4d detection, was 45% (9/20 cases). Compared with frozen-IF, the frozen-IHC technique presented an 85% concordance rate (17/20 cases; r = .70; P < .001; sensitivity = 77.8%; specificity = 90.9%). The paraffin-IF technique showed similar results, with an 80% concordance rate (16/20 cases; r = .64; P < .005; sensitivity = 55.6%; specificity = 100%), whereas C4d detection occurred in only 65% of paraffin-IHC cases (13/20; r = .30; not significant; sensitivity = 66.7%; specificity = 63.6%). No capillary C4d deposition was detected in cases without evidence of rejection. However, 4/7 cases (57%) of acute rejection were C4d positive. In the CAN group, 5/11 cases (45%) were C4d positive. In conclusion, these results demonstrated that frozen-IHC and paraffin-IF can be considered alternative techniques to frozen-IF for C4d detection. The paraffin-IHC technique displayed the lowest concordance rate for C4d detection.

Complement Fragment C4d and C3d Deposition in Pediatric Heart Receipients With a Positive Crossmatch

Pediatric heart transplant recipients with a positive complement-dependent cytotoxic (CDC) donor-recipient crossmatch are at high risk for rejection. We sought to correlate the pattern of C3d and C4d myocardial capillary deposition and pericapillary macrophage infiltration, possible markers of antibody-mediated rejection, to clinical evidence of rejection in these patients. Were studied 15 pre-sensitized pediatric patients who had 21 rejection episodes, as defined by International Society for Heart and Lung Transplantation (ISHLT) biopsy Grade >or=2R and/or the development of abnormal left ventricular (LV) function at >1 week after transplant. Archived paraffin-embedded endomyocardial biopsies (n = 74) from these patients were subjected to immunoperoxidase staining for C3d, C4d and CD68 in duplicate. Positive and negative controls were included for each assay. C3d deposition was present in 74 of 74 (100%) specimens. C4d deposition was present in 6 of 74 (8%) biopsies from 4 patients. Biopsies with C4d deposition had ISHLT Grade >or=2R cellular infiltration in 5 of 6 specimens. Pericapillary macrophage infiltration, defined as positive staining for CD68, was found in 34 of 74 (46%) biopsies, and was associated with ISHLT Grade >or=2R in 10 of 34 (29%). C3d deposition was universally present after heart transplantation with a CDC(+) donor/recipient crossmatch. C4d deposition and pericapillary macrophage infiltration were found with some, but not all, episodes of rejection. Further study is needed to understand the significance of the presence of complement fragments and pericapillary macrophage infiltration in these endomyocardial biopsies.

C4d deposition and cellular infiltrates as markers of acute rejection in rat models of orthotopic lung transplantation.

C4d is a useful marker of antibody-mediated rejection in cardiac and renal transplants, but clinical studies examining correlations between circulating alloantibodies, C4d deposition, and rejection in lung transplants have yielded conflicting results. We studied circulating alloantibody levels and C4d deposition in two rat models of lung transplantation: Brown Norway (BN) to Wistar-Kyoto (WKY) and PVG.R8 to PVG.1U lung allografts. The availability of C6 deficient (C6-) and C6 sufficient (C6+) PVG 1U rats allowed evaluation of the effects of the terminal complement components on graft injury and C4d deposition. The lung allografts had histologic features resembling human posttransplant capillaritis, characterized by neutrophilic infiltration of alveoli, edema, and hemorrhage. Immunoperoxidase stains on cross sections of allografts showed intense, diffuse, C4d deposition in a continuous linear pattern on the vascular endothelium. C4d deposits were found in both BN to WKY and PVG R8 to 1U allografts, whereas no staining was detectable in WKY to WKY isografts or native lungs. Complement deposition was associated with vascular disruption in C6+, but not in C6- recipients. The presence of circulating donor-specific alloantibodies was verified by flow cytometry. Cell-specific staining revealed perivascular accumulation of macrophages and T lymphocytes whereas neutrophils were sequestered in the intravascular and alveolar capillary compartments. The deposition of C4d on vascular endothelium as well as the coincident presence of alloantibodies is consistent with previous findings in antibody-mediated rejection of renal and cardiac transplants. Furthermore, the histological features of our allografts support the concept that posttransplant capillaritis is a form of humoral rejection.

Renal allograft biopsies in the era of C4d staining: the need for change in the Banff classification system

C4d immunostaining in the peritubular capillaries (PTC) is a marker of antibody-mediated rejection (AMR). We evaluated the histopathologic diagnoses of 388 renal transplant biopsies since the implementation of routine C4d immunostaining at our center. Of these, 155 (40%) biopsies had evidence of acute cellular rejection (ACR), out of which 119 (77%) had pure ACR, 31 (20%) had ACR with concomitant features of AMR, and five (3%) had ACR with focal C4d staining. Sixty-four (16%) biopsies exhibited features of AMR [33 (52%) pure AMR, and 31(48%) concomitant AMR and ACR]. One hundred and fifty-five (40%) biopsies had features of interstitial fibrosis and tubular atrophy (IFTA). Of these, 20 (13%) had concomitant AMR [13 (8.5%) had pure AMR and seven (4.5%) had concomitant ACR and AMR]. Creatinine at the time of biopsy was higher in patients with mixed ACR and AMR and the clinical behavior of mixed lesions is more aggressive over time. Despite having a lower serum creatinine at the time of biopsy, patients with IFTA experienced gradual decline in graft function over time. The pathologic findings in renal allograft biopsies are often mixed and mixed lesions appear to have more aggressive clinical behavior. These findings suggest the need for change in the Banff classification system to better capture the complexity of renal allograft pathologies.

Peritubular capillary C4d deposition in lupus nephritis different from antibody-mediated renal rejection

C4d deposition in peritubular capillaries (PTC) has been used as a marker of antibody-mediated rejection (AMR). However, PTC C4d deposition is not described in patients with lupus nephritis (LN). C4d deposition in PTC was detected in 455 patients with biopsy proven LN in the present study. Renal tissues from 21 cases of acute AMR served as controls. C4d deposition in PTC was found in 31 patients (6.81%) with LN. Patients with PTC C4d positive showed higher SLEDAI score and higher frequency of hypocomplementemia as compared to C4d negative. The prevalence of ANA, anti-dsDNA, anti-Sm and ACA were higher in C4d positive group, and most of these patients showed the diffuse proliferative glomerular lesion. In contrast with acute AMR, the staining pattern of C4d was granular deposition and the detection of C4d along PTC was accompanied by deposition of IgG and C1q or C3. Electron dense deposition on PTC was observed in most of LN patients. In conclusion, C4d deposition in PTC could be found in a small part of patients with LN. Our study suggested for the first time that C4d positive deposition were close relation with the higher disease activity of LN, and that immune complex formation might be involved in PTC C4d deposition in LN patients, Such PTC C4d deposition is distinct from that of AMR.