C4d-Positive Chronic Rejection: A Frequent Entity With a Poor Outcome

Early Versus Late Acute AMR in Kidney Transplant Recipients-A Comparison of Treatment Approaches and Outcomes From the ANZDATA Registry

BACKGROUND

Antibody-mediated rejection (AMR) is a major cause of kidney allograft failure and demonstrates different properties depending on whether it occurs early (<6 mo) or late (>6 mo) posttransplantation. We aimed to compare graft survival and treatment approaches for early and late AMR in Australia and New Zealand.

METHODS

Transplant characteristics were obtained for patients with an AMR episode reported to the Australia and New Zealand Dialysis and Transplant Registry from January 2003 to December 2019. The primary outcome of time to graft loss from AMR diagnosis, with death considered a competing risk, was compared between early and late AMR using flexible parametric survival models. Secondary outcomes included treatments used, response to treatment, and time from AMR diagnosis to death.

RESULTS

After adjustment for other explanatory factors, late AMR was associated with twice the risk of graft loss relative to early AMR. The risk was nonproportional over time, with early AMR having an increased early risk. Late AMR was also associated with an increased risk of death. Early AMR was treated more aggressively than late with more frequent use of plasma exchange and monoclonal/polyclonal antibodies. There was substantial variation in treatments used by transplant centers. Early AMR was reported to be more responsive to treatment than late.

CONCLUSIONS

Late AMR is associated with an increased risk of graft loss and death compared with early AMR. The marked heterogeneity in the treatment of AMR highlights the need for effective, new therapeutic options for these conditions.

Early recognition of chronic rejection in a face allotransplant patient with alopecia

The features of chronic rejection (CR) in full-face vascularized composite allotransplantation (VCA) are not well-known. Herein, we report a full-face transplant patient that experienced two episodes of acute rejection (AR) and three episodes of AR/CR over the course of 6-years. The patient noticed a small, round patch of hair loss in his beard 9 months after the second AR episode, which occurred 21 months post-transplantation. Biopsy of the alopecic patch showed lichen-planopilaris-like features, which was suggestive of early CR. Despite an increase in immunosuppressive dosages, the alopecia progressed. Following the second and third AR/CR episodes, the alopecia became more pronounced, with the addition of hyperpigmentation as well as sclerosis and telangiectasia. The findings of multiple biopsies showed CR. Based on these findings we think that alopecia with lichen-planopilaris-like histopathological features similar to grade III AR features, particularly in hair follicles appears to be an early finding of CR in the presented patient. The findings further indicate that follicular involvement may be a significant feature of CR in VCA patients and that it can present prior to sclerosis, vasculopathy, or loss of adnexa. The present case is uniquely important because of the distinctive presentation of CR, with hair follicles clinically and histopathologically affected, leading to progressive and irreversible alopecia with lichen-planopilaris-like histopathology.

Clinical significance of C4d deposition in renal tissues from patients with primary Sjögren's syndrome-a preliminary study

Background

To evaluate renal expression of C4d, a complement component in the classical/mannose binding lectin (MBL) pathway, in patients with primary Sjögren’s syndrome (pSS)-associated renal impairments.

Methods

We retrospectively reviewed the clinical and pathological data from 39 patients with pSS presenting with renal impairments. C4d was examined in paraffin-embedded biopsy tissues using immunohistochemistry. Glomerular C4d positive was defined when > 75% glomeruli were globally stained. Tubulointerstitial C4d (TI-C4d) were scored semi-quantitatively as 0 (absent), 1 (spotty or weak), 2 (patchy) and 3 (diffuse). A TI-C4d score ≥ 2 was considered TI-C4d positive and included in the TI-C4d⁺ group and vice versa. Peritubular capillary (PTC) C4d was scored as 0 (absent), 1 (0~10%, minimal), 2 (10%~ 50%, focal), and 3 (> 50%, diffuse).

Results

Glomerular C4d deposition was observed in all 8 patients with pSS-related membranous nephropathy (MN) without obvious C1q deposition. Two of 5 patients with mesangial proliferative glomerulonephritis and 1 of 2 patients with IgA nephropathy had mild mesangial C4d deposition. Sixteen patients (6 glomerular dominant and 10 tubulointerstitial dominant) presented TI-C4d score ≥ 2. Patients in the TI-C4d⁺ group exhibited a higher serum creatinine level at the time of renal biopsy (TI-C4d⁺ 132.5 [89.7, 165.5] vs. TI-C4d⁻ 83.0 [70.7, 102.0] μmol/L, P = 0.008). PTC C4d was observed in 12 patients, with each of minimal, focal and diffuse staining being noted in 4 patients.

Conclusions

The MBL pathway of complement activation was potentially involved in pSS-related MN. Tubulointerstitial C4d might be a pathological marker of severe renal injury in patients with pSS-related renal impairments.

Electronic supplementary material

The online version of this article (10.1186/s12882-019-1341-y) contains supplementary material, which is available to authorized users.

Failure to remove de novo donor-specific HLA antibodies is influenced by antibody properties and identifies kidney recipients with late antibody-mediated rejection destined to graft loss - a retrospective study

Current research is focusing on identifying bioclinical parameters for risk stratification of renal allograft loss, largely due to antibody-mediated rejection (AMR). We retrospectively investigated graft outcome predictors in 24 unsensitized pediatric kidney recipients developing HLA de novo donor-specific antibodies (dnDSAs), and treated for late AMR with plasmapheresis + low-dose IVIG + Rituximab or high-dose IVIG + Rituximab. Renal function and DSA properties were assessed before and longitudinally post treatment. The estimated GFR (eGFR) decline after treatment was dependent on a negative % eGFR variation in the year preceding treatment (P = 0.021) but not on eGFR at treatment (P = 0.74). At a median follow-up of 36 months from AMR diagnosis, 10 patients lost their graft. Altered eGFR (P < 0.001) and presence of C3d-binding DSAs (P = 0.005) at treatment, and failure to remove DSAs (P = 0.01) were negatively associated with graft survival in the univariable analysis. Given the relevance of DSA removal for therapeutic success, we analyzed antibody properties dictating resistance to anti-humoral treatment. In the multivariable analysis, C3d-binding ability (P < 0.05), but not C1q-binding, and high mean fluorescence intensity (P < 0.05) were independent factors characterizing DSAs scarcely susceptible to removal. The poor prognosis of late AMR is related to deterioration of graft function prior to treatment and failure to remove C3d binding and/or high-MFI DSAs.

Pediatric kidney transplantation

Since first performed in 1954, kidney transplantation has evolved as the preferred long-term treatment of children with end stage renal disease (ESRD). The etiology of chronic kidney disease (CKD) and ESRD in children is broad and can be quite complicated, necessitating a multidisciplinary team to adequately care for these patients and their myriad needs. Precise surgical techniques and modern protocols for immunosuppression provide excellent long-term patient and graft survival. This article reviews the many etiologies of renal failure in the pediatric population focusing on those most commonly leading to the need for kidney transplantation. The processes of evaluation, kidney transplantation, short-term and long-term complications, as well as long-term outcomes are also reviewed.

Positive C4d in kidney transplantation biopsy: clinical impact

BACKGROUND

Deposition of C4d in peritubular capillaries of renal graft is normally associated with the presence of antibody-mediated rejection. The clinical impact of its presence in patients with renal transplant in Colombia is uncertain, as well as the association in acute rejection and the response to the management and survival of the graft. The aim of this study was to determine the risk of having positive C4d in biopsies of patients with episodes of acute cellular rejection.

METHODS

We retrospectively reviewed 226 biopsies of kidney transplantation, all of them with acute rejection and histopathological findings classified according to Banff criteria 2009 and performed between January 2005 and December 2012 for graft dysfunction. C4d staining was performed by immunohistochemistry.

RESULTS

C4d staining was positive in 25 of 226 biopsies. Rejection time in patients with positive C4d was 15 months in average vs 8 months with negative C4d.

CONCLUSIONS

With the use of a multivariate analysis, we found that the unique risk for C4d in our population was the positive panel reactive antibodies and elapsed time between transplant and the rejection (odds ratio: 2.12, P = .034) and that the other variables analyzed are not related to the expression of C4d.

A systematic review of the role of C4d in the diagnosis of acute antibody-mediated rejection

In this study, we conducted a systematic review of the literature to re-evaluate the role of C4d in the diagnosis of acute antibody-mediated rejection of kidney allografts. Electronic databases were searched until September 2013. Eligible studies allowed derivation of diagnostic tables for the performance of C4d by immunofluorescence or immunohistochemistry with comparison to histopathological features of acute antibody-mediated rejection and/or donor-specific antibody (DSA) assays. Of 3492 unique abstracts, 29 studies encompassing 3485 indication and 868 surveillance biopsies were identified. Assessment of C4d by immunofluorescence and immunohistochemistry exhibited slight to moderate agreement with glomerulitis, peritubular capillaritis, solid-phase DSA assays, DSA with glomerulitis, and DSA with peritubular capillaritis. The sensitivity and specificity of C4d varied as a function of C4d and comparator test thresholds. Prognostically, the presence of C4d was associated with inferior allograft survival compared with DSA or histopathology alone. Thus, our findings support the presence of complement-dependent and -independent phenotypes of acute antibody-mediated rejection. Whether the presence of C4d in combination with histopathology or DSA should be considered for the diagnosis of acute antibody-mediated rejection warrants further study.

Effectiveness of rituximab and intravenous immunoglobulin therapy in renal transplant recipients with chronic active antibody-mediated rejection

BACKGROUND

Chronic active antibody-mediated rejection (CAMR) is an important cause of chronic kidney allograft dysfunction, but there has been no effective treatment protocol established for it.

METHODS

Six renal transplant recipients who showed progressive deterioration in graft function and CAMR as diagnosed by biopsy were enrolled. We administered a single dose of rituximab (375 mg/m(2)), followed by intravenous immunoglobulin (IVIg, 0.4 g/kg) for 4 days. The efficacy of this protocol was assessed on the basis of the improvement in allograft function, the amount of proteinuria, and the change in donor-specific antibodies (DSAs). We categorized the patients into 2 groups, responders and nonresponders, according to their response to the treatment.

RESULTS

All of the patients showed progressive deterioration of graft function before the diagnosis of CAMR. Luminex solid-phase assays showed that 3 patients had DSAs. After the treatment, allograft function improved or stabilized in 3 patients in the responder group, but still showed a deteriorating pattern in the nonresponder group. In the responder group, the amount of proteinuria also decreased after the treatment, but it increased in the nonresponder group. On diagnosis of CAMR, the nonresponders showed a longer posttransplantation period, a higher degree of transplant glomerulopathy, more severely deteriorated allograft function, and higher proteinuria compared with the responders.

CONCLUSIONS

The combination of rituximab and IVIg was effective in early-stage CAMR, but the effect was limited in the advanced stage.

The impact of pretransplant donor-specific antibodies on graft outcome in renal transplantation: a six-year follow-up study

OBJECTIVE

The significance of pretransplant, donor-specific antibodies on long-term patient outcomes is a subject of debate. This study evaluated the impact and the presence or absence of donor-specific antibodies after kidney transplantation on short- and long-term graft outcomes.

METHODS

We analyzed the frequency and dynamics of pretransplant donor-specific antibodies following renal transplantation from a randomized trial that was conducted from 2002 to 2004 and correlated these findings with patient outcomes through 2009. Transplants were performed against a complement-dependent T- and B-negative crossmatch. Pre- and posttransplant sera were available from 94 of the 118 patients (80%). Antibodies were detected using a solid-phase (Luminex®), single-bead assay, and all tests were performed simultaneously.

RESULTS

Sixteen patients exhibited pretransplant donor-specific antibodies, but only 3 of these patients (19%) developed antibody-mediated rejection and 2 of them experienced early graft losses. Excluding these 2 losses, 6 of 14 patients exhibited donor-specific antibodies at the final follow-up exam, whereas 8 of these patients (57%) exhibited complete clearance of the donor-specific antibodies. Five other patients developed ''de novo'' posttransplant donor-specific antibodies. Death-censored graft survival was similar in patients with pretransplant donor-specific and non-donor-specific antibodies after a mean follow-up period of 70 months.

CONCLUSION

Pretransplant donor-specific antibodies with a negative complement-dependent cytotoxicity crossmatch are associated with a risk for the development of antibody-mediated rejection, although survival rates are similar when patients transpose the first months after receiving the graft. Our data also suggest that early posttransplant donor-specific antibody monitoring should increase knowledge of antibody dynamics and their impact on long-term graft outcome.

Plasma proteome changes associated with refractory cytopenia with multilineage dysplasia

BACKGROUND

Refractory cytopenia with multilineage dysplasia (RCMD) is a subgroup of myelodysplastic syndrome (MDS), which belongs to oncohematological diseases, occurring particularly in elderly patients, and represents a heterogeneous group of bone marrow diseases. The goal of this study was to look for plasma proteins that changed quantitatively or qualitatively in RCMD patients.

RESULTS

A total of 46 plasma samples were depleted, proteins were separated by 2D SDS-PAGE (pI 4-7), and proteomes were compared using Progenesis SameSpots statistical software. Proteins were identified by nanoLC-MS/MS. Sixty-one unique, significantly (p < 0.05, ANOVA) different spots were found; proteins in 59 spots were successfully identified and corresponded to 57 different proteins. Protein fragmentation was observed in several proteins: complement C4-A, complement C4-B, inter-alpha-trypsin inhibitor heavy chain H4, and endorepellin.

CONCLUSIONS

This study describes proteins, which change quantitatively or qualitatively in RCMD patients, and represents the first report on significant alterations in C4-A and C4-B complement proteins and ITIH4 fragments in patients with MDS-RCMD.

Optimal cutoff point for immunoperoxidase detection of C4d in the renal allograft: results from a multicenter study

BACKGROUND

Although C4d deposition in peritubular capillaries has been identified as a strong risk factor for subsequent renal allograft loss, the optimal cutoff for the fraction of peritubular capillaries needed to establish a positive stain in formalin-fixed, paraffin-embedded material has not been defined systematically. The objective of this study was to establish the threshold for positive staining that best predicts renal outcome in renal biopsies in a multicenter study in which local and central pathologic conditions were compared.

METHODS

Unstained renal biopsy slides were obtained from 296 patients. The percentage of peritubular capillaries staining positively for C4d was detected by immunoperoxidase staining.

RESULTS

The percentage C4d deposition ranged from 0% to 90% with 44% (129/296) having a positive percentage of C4d staining. The median for positive cases was 25%. Local C4d+ results were reported qualitatively, with 28% recorded as positive for C4d. Using a centrally determined cutoff of 10%, tests for agreement of local and central C4d staining were fair (κ 0.40, 95% confidence interval 0.29-0.51). Raising the centrally determined cutoff to 25% or 50% did not change the κ values (0.44 and 0.41, respectively). By Cox proportional hazards model, C4d positivity (centrally determined assessment) using a cutoff of 10% was the strongest predictor of time to graft loss (hazard ratio 2.66, 95% confidence interval 1.68-4.21). Centrally determined C4d positivity correlated with Banff scores indicative of acute inflammation but not with scores indicative of fibrosis/atrophy or transplant glomerulopathy.

CONCLUSIONS

Our findings indicate that C4d positivity, defined as more than or equal to 10% by immunoperoxidase, is a strong predictor of graft loss.

Significance of peritubular capillary, glomerular, and arteriolar C4d staining patterns in paraffin sections of early kidney transplant biopsies

BACKGROUND

Although diffuse linear C4d deposition in peritubular capillaries (PTCs) is a well-established criterion of alloantibody-mediated kidney transplant rejection, the actual relevance of focal or granular C4d deposits or staining outside PTC (glomeruli and arterioles) has yet to be established.

METHODS

This study was designed to evaluate the diagnostic significance of such nontypical C4d staining patterns. A total of 539 early indication biopsies (329 kidney transplants) were analyzed by immunohistochemistry using a polyclonal anti-C4d antibody.

RESULTS

We found a close interrelationship between diffuse or focal linear C4d deposition in PTC, linear endothelial deposition in glomeruli, and arteriolar C4d. These specific patterns were also related to transplant glomerulitis and recipient presensitization. No such associations, however, were observed for other patterns, such as granular C4d in PTC. Detection of diffuse but not focal linear C4d in PTC was found to be associated with adverse allograft survival (5-year death-censored graft survival: 48% vs. 82%, 89%, or 84% in patients with focal, minimal, or no C4d, respectively; P<0.0001). Univariate analysis also revealed inferior graft survival in recipients with linear C4d in glomeruli (P=0.02). Applying multivariate Cox regression analysis, however, only diffuse linear PTC staining was found to be predictive of graft loss (hazard ratio 3.95 [95% confidence interval 1.62-9.60]; P=0.002).

CONCLUSION

There might be a relationship between humoral alloimmunity and distinct less established staining patterns, such as focal linear C4d in PTC, endothelial C4d in glomeruli, or arteriolar C4d. Nevertheless, our results reemphasize the prognostic value of diffuse linear PTC staining.

Immunohistochemical characterization of glomerular and tubulointerstitial infiltrates in renal transplant patients with chronic allograft dysfunction

BACKGROUND

The term chronic allograft nephropathy (CAN) was deleted in the Eighth Banff Classification and two new categories were introduced: chronic T-cell-mediated rejection (CTMR) and chronic active humoral rejection (CAHR). The aim of this study was to revise our CAN cases diagnosed in the last 4 years, analyse allograft survival rates and identify types of infiltrating cells in the different settings.

METHODS

Seventy-nine patients with biopsy-proven CAN were examined and classified into four groups according to the Banff 2005 criteria: CTMR, CAHR, chronic calcineurin inhibitor toxicity (CNITOX) and interstitial fibrosis and tubular atrophy not otherwise specified (NOS). CD4, CD8, CD20, CD68, CD103, Foxp3 and IL-17 protein expression and C4d deposits were investigated.

RESULTS

We diagnosed 20 CTMR, 13 CAHR, 28 CNITOX, and 18 NOS. Death-censored graft survival at 4 years from renal biopsy was worse in CAHR compared with the other types of chronic injury. Glomerular CD8(+) cells were increased in CTMR vs CNITOX and NOS. Interstitial CD4(+) and CD8(+) cells were increased in CTMR vs CNITOX. CD68(+) cells in glomerular and peritubular capillaries were higher in CAHR vs CNITOX, CTMR and NOS. CD103(+) cells were higher in cases with tubulitis than in those without. T regulatory and T helper 17 cells were rarely observed in the different settings.

CONCLUSIONS

Graft survival was worse in patients with CAHR. The presence of any grade transplant glomerulopathy and chronic allograft vasculopathy are poorer prognostic factors. Infiltrating CD8(+), CD103(+) and CD4(+) cells may help to differentiate CTMR from other types of chronic injury, thus improving diagnostic/prognostic features of biopsy in patients with chronic allograft dysfunction.

Treatment strategies to minimize or prevent chronic allograft dysfunction in pediatric renal transplant recipients: an overview

Long-term allograft survival poses a major problem in pediatric renal transplantation, with allograft nephropathy being the principal cause of graft failure after the first post-transplant year. The mechanisms of nephron loss resulting in graft dysfunction are multiple, comprising both immunologic factors such as acute and chronic antibody- or T-cell-mediated rejection and non-immunologic components. The latter include peri-transplant injuries and renovascular lesions (renal artery stenosis, thrombosis) as well as cardiovascular risk factors such as arterial hypertension and hyperlipidemia. Another relevant issue leading to progressive nephron loss and declining kidney transplant function is acute and chronic nephrotoxicity induced by the calcineurin inhibitors (CNIs) ciclosporin (cyclosporine microemulsion) and tacrolimus. Furthermore, the presence of an abnormal lower urinary tract as well as bacterial (recurrent pyelonephritis) and viral (cytomegalovirus [CMV], polyomavirus [BK virus; BKV]) infections are crucial factors involved in the incidence of chronic allograft dysfunction and graft failure. Renovascular lesions and lower urinary tract obstruction are typical indicators for surgical intervention. The aim of treatment in pediatric patients with renal failure secondary to a dysfunctional lower urinary tract is to create a sterile, continent, and nonrefluxive reservoir. Surgical techniques such as bladder augmentation and the introduction of intermittent catheterization and anticholinergic therapy have significantly improved graft outcome. Arterial hypertension, another factor responsible for graft function deterioration in pediatric renal transplant recipients, is controlled preferably by the use of angiotensin converting enzyme (ACE) inhibitors or angiotensin II receptor antagonists, which are known to possess nephroprotective properties in addition to their potent antihypertensive effects. Although treatment of subclinical rejection with augmented immunosuppression has been associated with better graft survival, an increase of the immunosuppressive level to avoid subclinical rejection should be weighed against the risk of infection. The majority of viral infections affecting kidney allografts are caused by CMV and BKV. Antiviral CMV prophylaxis or pre-emptive therapy with ganciclovir has been shown to have beneficial effects in the pediatric renal transplant population. Treatment of BKV-induced nephropathy is based on reduction of the immunosuppressant therapy, although specific antiviral agents such as cidofovir and leflunomide are known to inhibit BKV. However, cidofovir itself is nephrotoxic and should therefore be administered cautiously to pediatric renal transplant patients. Since CNIs are likewise known for their nephrotoxic effects, especially with long-term use, alteration of the immunosuppressant regimen is necessary in case of deteriorating graft function due to CNI-induced histopathologic changes. Complete CNI avoidance seems inappropriate because, in this situation in pediatric renal transplant recipients, other relatively potent immunosuppressant agents such as lymphocyte-depleting antibodies, which are frequently accompanied by a higher incidence of infections, are needed for rejection prophylaxis. CNI withdrawal and switching of the immunosuppressant regimen from CNI therapy to sirolimus may be an option for some pediatric renal transplant patients with less advanced graft function deterioration. Nevertheless, potential adverse events such as aggravation of proteinuria, hyperlipidemia, myelosuppression, and hypergonadotropic hypogonadism have to be considered, and controlled studies are lacking. At present, an immunosuppressant maintenance therapy composed of low-dose tacrolimus or ciclosporin (CNI minimization) and mycophenolate mofetil with low-dose corticosteroids appears to be the most promising strategy to adopt in pediatric renal transplant recipients at low or normal immunologic risk.

The impact of c4d pattern and donor-specific antibody on graft survival in recipients requiring indication renal allograft biopsy

We examined the pattern of PTC C4d by immunohistochemistry and DSA in 297 kidney recipients with indication biopsies, and evaluated their predictive value for graft survival. Median biopsy time was 5.1 months posttransplant. Patients were followed for 17.9 +/- 9.4 months postbiopsy. An 18.5% had focal and 15.2% had diffuse C4d, with comparable graft survival (adjusted graft failure HR: 2.3, p = 0.001; HR:1.9, p < 0.02, respectively). 31.3% were DSA+, 19.5% class I and 22.9% class II DSA. Only those with class II DSA had worse outcome (adjusted HR:2.5, p = 0.001 for class II only; HR:2.7, p < 0.001 for class I/II DSA). Among patients with <10%C4d, 23.9% had DSA, compared to 68.9% with diffuse staining. For patients biopsied in first-year posttransplant presence of DSA, regardless of C4d positivity in biopsy, was a poor prognostic factor (adjusted graft failure HR: 4.2, p < 0.02 for C4d-/DSA+; HR:4.9, p = 0.001 for C4d+/DSA+), unlike those biopsied later. We have shown that focal C4d had similar impact on graft survival as diffuse pattern. During the first-year posttransplant either class I or II DSA, and afterward only class II DSA were associated with worse graft survival. DSA was predictive of worse outcome regardless of C4d for patients biopsied in first year and only with C4d positivity afterward, supporting the importance of assessment of both DSA and C4d pattern in biopsy.

KDIGO clinical practice guideline for the care of kidney transplant recipients

The 2009 Kidney Disease: Improving Global Outcomes (KDIGO) clinical practice guideline on the monitoring, management, and treatment of kidney transplant recipients is intended to assist the practitioner caring for adults and children after kidney transplantation. The guideline development process followed an evidence-based approach, and management recommendations are based on systematic reviews of relevant treatment trials. Critical appraisal of the quality of the evidence and the strength of recommendations followed the Grades of Recommendation Assessment, Development, and Evaluation (GRADE) approach. The guideline makes recommendations for immunosuppression, graft monitoring, as well as prevention and treatment of infection, cardiovascular disease, malignancy, and other complications that are common in kidney transplant recipients, including hematological and bone disorders. Limitations of the evidence, especially on the lack of definitive clinical outcome trials, are discussed and suggestions are provided for future research.

Combination of peritubular c4d and transplant glomerulopathy predicts late renal allograft failure

The histologic associations and clinical implications of peritubular capillary C4d staining from long-term renal allografts are unknown. We identified 99 renal transplant patients who underwent an allograft biopsy for renal dysfunction at least 10 yr after transplantation, 25 of whom were C4d-positive and 74 of whom were C4d-negative. The average time of the index biopsy from transplantation was 14 yr in both groups. Compared with C4d-negative patients, C4d-positive patients were younger at transplantation (29 +/- 13 versus 38 +/- 12 yr; P < 0.05) and were more likely to have received an allograft from a living donor (65 versus 35%; P < 0.001). C4d-positive patients had more inflammation, were more likely to have transplant glomerulopathy, and had worse graft outcome. The combined presence of C4d positivity, transplant glomerulopathy, and serum creatinine of >2.3 mg/dl at biopsy were very strong predictors of rapid graft loss. C4d alone did not independently predict graft loss. Retrospective staining of historical samples from C4d-positive patients demonstrated C4d deposition in the majority of cases. In summary, these data show that in long-term renal allografts, peritubular capillary staining for C4d occurs in approximately 25% of biopsies, can persist for many years after transplantation, and strongly predicts graft loss when combined with transplant glomerulopathy.

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.

Chronic allograft dysfunction-is there a treatment?

BACKGROUND

The major causes of renal transplant loss are death and chronic allograft dysfunction (CAD). The aims of this study were to determine the incidence of CAD in our population and the relation between allograft survival and immunosuppressive regimens.

METHODS

We studied retrospectively 473 patients who received deceased donor kidney transplants with at least 1 allograft biopsy between January 1990 and May 2007. Clinical data included age, gender, biopsy data, and immunosuppression before and after kidney biopsy. Mean age was 45.4 +/- 12.7 years including 65% males with a mean follow-up of 6.7 +/- 4.5 years. CAD was observed in 177 of 473 biopsies: 48 patients showed interstitial fibrosis (IF); 101 chronic rejection (CR); 16 transplant glomerulopathy (TG); and 12, CR and TG. Mean follow-up since the discovery of the histologic feature was 60.5 +/- 50.5 months for IF; 38.3 +/- 40.8 for CR, and 18.2 +/- 19.2 for TG.

RESULTS

CAD, which was more common in younger patients (P = .03), correlated upon univariate and multivariate analysis with CKD stage 5d development (P < .001). Deposition of C4d in peritubular capillaries was more frequent among CAD patients (P = .004), an association with particular relevance to recipients with CR (P = .02) and TG (P < .001). When we analyzed CAD subpopulation, we observed a positive correlation between allograft survival and immunosuppression modification after biopsy. Substitution of sirolimus (40/177) was shown in univariate, multivariate and Cox regression analyses to be a renal protector (P < .002). Allograft survival was also correlated with initial mycophenolate mofetil versus azathioprine, (62/177) immunosuppression (P < .001).

CONCLUSION

CAD, a frequent histologic feature, may benefit from sirolimus conversion.

Focal C4d+ in renal allografts is associated with the presence of donor-specific antibodies and decreased allograft survival

Diffuse peritubular capillary C4d deposition in renal allograft biopsies is associated with donor-specific antibodies (DSA) and graft failure. The significance of focal C4d+ is unclear. We reviewed 368 biopsies from 301 patients performed for renal dysfunction or proteinuria over 5 years. Diffuse C4d+, focal C4d+ and C4d- detected by immunofluorescence occurred in 9.5%, 20.9% and 69.4% of biopsies, respectively. Patients were similar in gender, age, cause of renal disease, donor source, HLA mismatch, serum creatinine at baseline and interval from transplantation to biopsy. Diffuse and focal C4d+ were associated with acute cellular rejection (p < 0.001). Transplant glomerulopathy was associated with diffuse C4d+. DSA at the time of biopsy, were positive in 79.3% of diffusely C4d+ patients, 68.8% of those with focal C4d+ (p = 0.27) and 9.9% of patients with C4d- (p < 0.001, compared to either the focal or diffuse groups, respectively). Allograft survival at 40 months was lower in diffuse C4d+ compared to the C4d- group (p = 0.014), but not when compared to the focal C4d+ group. There was a clear trend toward worse graft survival in patients with focal C4d+ in this time interval, but focal C4d+ compared to both diffuse C4d+ and C4d-groups was not statistically significant (p = 0.08).

Successful treatment of chronic antibody-mediated rejection with IVIG and rituximab in pediatric renal transplant recipients

BACKGROUND

Chronic antibody-mediated rejection (CAMR) of renal allografts has recently been recognized as a defined nosologic entity. The outcome of CAMR is poor; there is no established treatment protocol for this condition. We therefore initiated a pilot study on treatment of CAMR with an antihumoral regimen consisting of high-dose intravenous immunoglobulin (IVIG) and the chimeric anti-CD20 antibody rituximab.

METHODS

Six pediatric renal transplant recipients with CAMR received four weekly doses of IVIG (1 g/kg body weight per dose), followed by a single dose of rituximab (375 mg/m2 body surface area) 1 week after the last IVIG infusion. Renal allograft biopsies were evaluated using the Banff '05 classification. Human leukocyte antigen-specific antibodies were detected by panel-reactive lymphocytotoxicity and solid phase ELISA assays.

RESULTS

Median glomerular filtration rate during 6 months before intervention dropped by 25 (range, 11-26) mL/min/1.73 m2 (P<0.05) and increased in response to antihumoral therapy by 21 (-14 to +30) 6 months (P<0.05) and by 19 (-14 to +23) mL/min/1.73 m2 12 months (P=0.063) after start of treatment. Glomerular filtration rate improved or stabilized in 4 patients; the two nonresponders had the highest degree of transplant glomerulopathy, the highest degree of C4d deposition in peritubular capillaries and pronounced interstitial inflammation. The treatment regimen was well tolerated.

CONCLUSION

This pilot study demonstrates that CAMR in pediatric renal transplant recipients can be treated successfully and safely with a combination of IVIG and rituximab. This observation should encourage more extensive studies to evaluate this new treatment strategy.