C4d Deposition In Peritubular Capillaries Research Articles

De novo membranous nephropathy and antibody‐mediated rejection in transplanted kidney

The etiology of de novo membranous nephropathy (MN) after kidney transplantation is still uncertain. Immunological response to various allograft antigens is speculated to be a candidate for the etiology. Seventeen patients with post-transplant de novo MN were studied clinically and pathologically in comparison with control post-transplant patients without MN. Double immunofluorescent staining was performed to identify the presence of donor-specific human leukocyte antigen (HLA) combined with IgG in the deposits on glomerular capillary walls. De novo MN occurs in relatively late period after transplantation (102.1 ± 68.3 months), presenting various degree of proteinuria. Histological findings associated with antibody-mediated rejection (AMR), such as peritubular capillaritis and C4d deposition in peritubular capillary, were more frequently observed in the patients with de novo MN than the non-MN control patients. Donor-specific antibody (DSA) was detected in five patients at the time of biopsy. In one case of de novo MN with DSA, a donor-derived HLA was identified in the subepithelial deposits on the glomerular capillary walls combined with IgG deposition. DSA and AMR might play some roles for the pathogenesis in some patients with de novo MN after kidney transplantation.

Significance of Peritubular Capillary, Glomerular, and Arteriolar C4d Staining Patterns in Paraffin Sections of Early Kidney Transplant Biopsies

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. 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. 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). 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.

The Role of Proteasome Inhibition With Bortezomib in the Treatment of Antibody-Mediated Rejection After Kidney-Only or Kidney-Combined Organ Transplantation

We report our initial experience in using the proteasome inhibitor, bortezomib, to treat established antibody-mediated rejection (AMR) in 20 patients. There were 16 kidney-only and 4 kidney-combined organ recipients with de novo donor-specific antibody (DSA) and histologic evidence of AMR with peritubular capillaries C4d deposition. AMR was diagnosed 19.8 months (range 1-71 months) posttransplant. Patients received intravenous corticosteroids followed by a 2-week cycle on days 1-4-8-11 of plasmapheresis and 1.3 mg/m² bortezomib; then 0.5 mg/kg intravenous immunoglobulin four times. De novo class I DSA was detected in 11 (55%) and class II DSA in 18 (90%) recipients. The absolute mean difference between peak-nadir dominant DSA was 68,171 molecules of equivalent soluble fluorochrome (P<0.0001), representing 55%±22%. Only two patients (10%) had undetectable DSA after treatment. Patient survival is 100%, and graft survival is 85% with a mean follow-up of 9.8 months (range 2-20 months). The treatment was generally well tolerated but caused fatigue, gastrointestinal complaints, fluid retention, and thrombocytopenia in a number of patients. The last follow-up estimated glomerular filtration rate was 41.9±16.8 mL/min (range 20.6-72.2 mL/min). However, only 25% returned to their baseline renal function before AMR, and many have proteinuria with urine protein/creatinine more than 0.5 in 41% and more than 1.0 in 18%. The bortezomib-containing regimen demonstrated activity in AMR but seems to be most effective before the onset of significant renal dysfunction (serum creatinine <3 mg/dL) or proteinuria (<1 g/day). The best use of bortezomib to treat AMR should be evaluated in controlled trials using dosing strategies that include longer courses or retreatment schedules.

Optimal Cutoff Point for Immunoperoxidase Detection of C4d in the Renal Allograft: Results From a Multicenter Study

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. Unstained renal biopsy slides were obtained from 296 patients. The percentage of peritubular capillaries staining positively for C4d was detected by immunoperoxidase staining. 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. Our findings indicate that C4d positivity, defined as more than or equal to 10% by immunoperoxidase, is a strong predictor of graft loss.

C4d-Fixing Capability of Low-Level Donor-Specific HLA Antibodies Is Not Predictive for Early Antibody-Mediated Rejection

Recent studies indicate that not all low-level donor-specific human leukocyte antigen (HLA) antibodies (HLA-DSA) (i.e., positive by solid-phase assays, negative by complement-dependent cytotoxic-crossmatch) have a detrimental clinical impact. The aim of this study was to investigate whether the pretransplant C4d-fixing capability allows distinguishing harmful from presumably clinically irrelevant HLA-DSA. We retrospectively investigated 64 patients with low-level HLA-DSA detected by single-antigen flow beads (SAFB). Thirty-four of 64 patients (53%) experienced early antibody-mediated rejection (AMR), whereas 30 patients (47%) did not. HLA-DSA characteristics (i.e., number, class, and strength), frequency of retransplants, and immunosuppressive regimens were not different in these two groups. Pretransplant sera were reanalyzed using a modified SAFB assay measuring C4d fixation induced by HLA antibodies. C4d-fixing HLA-DSA were observed in 11 of 64 patients (17%). AMR occurred in 6 of 11 patients (55%) with C4d-fixing HLA-DSA and in 28 of 53 patients (53%) without C4d-fixing HLA-DSA (P=1.0). Positive C4d staining in peritubular capillaries was detected in 6 of 11 patients (55%) with C4d-fixing HLA-DSA and in 21 of 53 patients (40%) without C4d-fixing HLA-DSA (P=0.50). The pretransplant capability of low-level HLA-DSA to trigger C4d fixation in vitro is not predictive for early AMR or C4d deposition in peritubular capillaries in vivo. This argues against pretransplant C4d SAFB testing to define the clinical relevance of low-level HLA-DSA.

Clinicopathological analysis of acute vascular rejection cases after renal transplantation

Histopathological change of acute vascular rejection (AVR) is characterized by intimal arteritis and transmural arteritis. In this report, we discuss the clinicopathological analysis of AVR cases after renal transplantation (RTX). AVR was diagnosed in 17 patients from 17 renal transplant patients followed in our institute between January 2003 and September 2008. We retrospectively reviewed these 17 patients. Among 17 cases of AVR, 10 cases were mild (v1 in Banff 07 classification), five were moderate (v2), and two were severe (v3). Interstitial inflammation (i1-i3) was present in all 17 biopsies. Moderate to severe tubulitis (t2-t3) was present in seven biopsies, and transplant glomerulitis (g1-g3) was present in 11, peritubular capillaritis (ptc1-ptc3) was in 15 of 17 biopsies. C4d deposition in peritubular capillary (PTC) was observed in 6 of 17 cases. By assaying with plastic beads coated with anti-human leukocyte antigen (HLA) antigen performed in 17 cases, the circulating ant-HLA alloantibody was detected in 10 patients, of which 5/10 were donor-specific antibodies (DSA). Acute antibody-mediated rejection (AAMR) was diagnosed in three cases. Many of v1 cases, steroid pulse therapy (SP) were effective. In v2 and v3 cases, six of seven were steroid-resistant rejection and were need more anti-rejection therapy (ART), such as muromonab CD3 (OKT3) injection, gusperimus (DSG) injection, plasmapheresis, intravenous immune globulin, and injection of rituximab. Ten of 17 patients recovered their renal allograft functions by ART, and 16 of 17 patients' grafts are functioning. Deterioration of renal allografts' function after biopsies was seen in seven patients with one of them lost their graft. In some cases, AVR might be provoked by anti-donor antibodies. The prognosis of the graft exhibiting AVR was relatively good in present immunosuppression and ART.

Early Humoral-Mediated Graft Injuries in ABO-Incompatible Kidney Transplantation in Human Beings

IntroductionAcute humoral rejection is the most important risk factor for early graft loss in ABO-incompatible (ABO-i) renal transplantation (RTx) and is present from the early period after RTx. However, the characteristics of early humoral-mediated graft injury are pathologically uncertain. ObjectiveTo analyze tissue from 10 protocol graft biopsies performed in 10 patients within 30 days post-RTx to clarify the pathologic features of early humoral-mediated graft injuries in ABO-i RTx. MethodsPathologic findings were examined using light and electron microscopy and immunofluorescence studies for C4d. Protocol biopsies were performed within 30 days after RTx in the absence of an episode of dysfunction (creatinine concentration 1.21–1.81 mg/dL). ResultsThe immunofluorescence study demonstrated C4d deposition in peritubular and glomerular capillaries. Acute glomerulitis with infiltration of mononuclear cells and neutrophils was observed in 3 patients. Furthermore, glomerulitis was accompanied by endothelial cell injuries, widening of subendothelial spaces with a double-contoured glomerular basement membrane, and mesangiolysis. ConclusionIn ABO-i RTx, early humoral-mediated graft injuries were observed in approximately 30% of patients despite normal graft function. They were characterized by C4d deposition and glomerular capillary injury. These findings suggest that renal glomeruli are the first site of graft injury by anti-A or anti-B blood type antibody with complement activation in ABO-i RTx.

Therapeutic Targeting of Classical and Lectin Pathways of Complement Protects from Ischemia-Reperfusion-Induced Renal Damage

Ischemia-reperfusion injury is the major cause of delayed graft function in transplanted kidneys, an early event significantly affecting long-term graft function and survival. Several studies in rodents suggest that the alternative pathway of the complement system plays a pivotal role in renal ischemia-reperfusion injury. However, limited information is currently available from humans and larger animals. Here we demonstrated that 30 minutes of ischemia resulted in the induction of C4d/C1q, C4d/MLB, and MBL/MASP-2 deposits in a swine model of ischemia-reperfusion injury. The infusion of C1-inhibitor led to a significant reduction in peritubular capillary and glomerular C4d and C5b-9 deposition. Moreover, complement-inhibiting treatment significantly reduced the numbers of infiltrating CD163(+), SWC3a(+), CD4a(+), and CD8a(+) cells. C1-inhibitor administration led to significant inhibition of tubular damage and tubular epithelial cells apoptosis. Interestingly, we report that focal C4d-deposition colocalizes with C1q and MBL at the peritubular and glomerular capillary levels also in patients with delayed graft function. In conclusion, we demonstrated the activation and a pathogenic role of classical and lectin pathways of complement in a swine model of ischemia-reperfusion-induced renal damage. Therefore, inhibition of these two pathways might represent a novel therapeutic approach in the prevention of delayed graft function in kidney transplant recipients.

Mechanism of Acute Antibody-Mediated Rejection in ABO-Incompatible Kidney Transplantation: Which Anti-A/Anti-B Antibodies are Responsible, Natural or de Novo?

Mechanism of Acute Antibody-Mediated Rejection in ABO-Incompatible Kidney Transplantation: Which Anti-A/Anti-B Antibodies are Responsible, Natural or de Novo?

97-P: Detection of serum antibody in renal allografts with focal peritubular capillary C4d deposition

97-P: Detection of serum antibody in renal allografts with focal peritubular capillary C4d deposition

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.

Clinicopathological analysis of transplant glomerulopathy cases

Transplant glomerulopathy (TG) is involved in the criteria of chronic active antibody-mediated rejection (c-AMR) in Banff 07 classification. In this report, we discuss the clinico-pathological analysis of TG cases after renal transplantation, and analysis of whether all TG cases are applied to c-AMR. Transplant glomerulopathy, defined by double contours of glomerular basement membranes, was diagnosed in 13 patients from 13 renal transplant patients followed-up in our institute between January 2007 and April 2008. We retrospectively reviewed these 13 patients. Among 13 cases of TG, three cases were mild (cg1 in Banff classification), four were moderate (cg2), and six were severe (cg3). Transplant glomerulitis and interstitial inflammation were present in all 13 biopsies, and peritubular capillaritis was present in 12 of 13 biopsies, interstitial fibrosis/tubular atrophy in 13, and the thickening of the peritubular capillary (PTC) basement membrane in 11. PTC C4d deposition was presented in six cases, three out of six cases had diffuse C4d deposits in PTC, and the remainder had focal deposits. By assaying with plastic beads coated with human leukocyte antigen (HLA) in 12 cases, the circulating anti-HLA alloantibody was detected in all 12 patients of which only 3 of 12 were donor-specific antibodies (DSA). In our cases, there was no patient who fully met criteria for c-AMR in Banff classification, which included TG, C4d deposition in PTC, and existence of DSA, but seven patients were diagnosed suspicious for c-AMR. Seven cases (54%) had proteinuria at the time of the biopsies and the severity of proteinuria was associated with the severity of TG. Deterioration of renal allografts' function after biopsies was seen in seven (54%), and two of them lost their graft. We suggest that histopathological changes of TG accompanied by transplant glomerulitis, peritubular capillaritis, the thickening of the peritubular capillaries basement membrane, and circulating anti-HLA antibodies may indicate c-AMR, even if C4d deposition in PTC is negative. The severity of TG may be associated with proteinuria, reduced graft function, and reduced graft survival.

Wiener Erfahrung mit ABO-inkompatibler Lebendnierentransplantation

ABO-incompatible kidney transplantation is a promising strategy for enlargement of living-donor pools. In recent years, recipient desensitization by blood group antigen-specific immunoadsorption, together with rituximab and intravenous immunoglobulin, has allowed excellent graft performance after ABO-incompatible transplantation. Adopting this protocol, originally described by Tydén and coworkers, we performed four living-donor renal transplants across the ABO barrier (A1-->0, A1-->B, B-->A1, A2-->0) between July 2007 and August 2008. Recipients were aged 25-66 years, donors 49-69 years. A protocol of on-demand immunoadsorption was followed, based on serial post-transplant antibody monitoring. Substantial and sustained decrease of blood group antibody levels was achieved in all four recipients, therefore post-transplant immunoadsorption was not needed. Graft and patient survival after 4-18 months' follow-up was 100%. Current serum creatinine was 1.3-2.0 mg/dl. Two grafts showed C4d deposits in peritubular capillaries in the complete absence of typical morphological features of antibody-mediated rejection. One recipient experienced early graft dysfunction, diagnosed as Banff borderline lesion, which responded well to steroid pulse therapy. The same recipient developed de novo interstitial fibrosis/tubular atrophy and arteriolar hyalinosis, presumably the result of suboptimal control of blood pressure and/or calcineurin inhibitor therapy. Two of the four recipients developed lymphoceles necessitating surgical revision. Apart from urinary tract infection in three patients and subclinical CMV in one, no major infectious complications were reported. Notably, two stable recipients developed polyoma BK viremia without clinical or morphological manifestations of polyomavirus-associated nephropathy. The results obtained in our small series support the earlier reported high efficiency of desensitization based on antigen-specific immunoadsorption. Nevertheless, the lack of long-term data will necessitate continuous and prudent consideration of the benefits and risks of this strategy.

Neutrophilic Tubulitis as a Marker for Urinary Tract Infection in Renal Allograft Biopsies With C4d Deposition

Neutrophilic tubulitis accompanied by intratubular neutrophil clusters in the renal allograft is a surrogate marker for urinary tract infection (UTI). Overlapping histologic findings can occur in antibody-mediated rejection, which is characterized by peritubular capillary (PTC) deposition of C4d. This study evaluated the incidence of UTI in biopsies with concurrent neutrophilic tubulitis and PTC C4d staining. Thirty-three allograft biopsies from 27 patients selected for the presence of simultaneous C4d staining and neutrophilic tubulitis were correlated with urine culture (U/C) results. U/C obtained on the same day as the biopsy confirmed UTI in 13 of 33 (39%) biopsies. Among 20 patients with negative U/C; prior culture results within 10 days of the biopsy were available for nine patients, and 5 of 9 (55%) were positive. Thus, UTI was confirmed in 18 of 33 (54%) biopsies. Biopsy interpretation and clinical management was confounded by changes of concurrent acute cellular rejection and antibody-mediated rejection confirmed by demonstration of donor-specific antibodies. Combined therapy with antibiotics and antirejection medications (ART) was administered to 12 of 18 (67%) patients. Neutrophilic tubulitis accompanied by neutrophil clusters in the tubular lumen is a useful marker of UTI, even in the presence of PTC C4d deposition. Therapeutic response to antibiotics is limited by co-existent T-cell or antibody-mediated rejection and underlying chronic allograft nephropathy.

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.

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).

Transplant Glomerulopathy: Clinical and Pathological Correlations

Objective Chronic transplant glomerulopathy (TG) is one of the leading causes of severe posttransplantation proteinuria and graft loss. Our current knowledge about risk factors for the development of TG, as well as factors that affect its dynamics and prognosis, is poor. We sought to describe the pathological and clinical risk factors and correlations of TG as well as parameters that influenced the survival of grafts with that pathology. Materials and Methods We retrospectively reevaluated 86 kidney transplant cases with TG that have been recognized on the basis of an indication biopsy since 1997. All TG as well as all pre-TG (previous) biopsies were characterized for the presence of C4d deposits in the graft. Results Younger recipient age and minimal immunosuppression due to drug withdrawal or suboptimal drug doses/blood levels within 3 to 6 months preceding the biopsy were associated with C4d deposition in peritubular capillaries (PTC; P = .0053 and P = .0365, respectively). Diffuse PTC-itis ( P = .029, RR [95% confidence interval] = 3.349 [1.131–9.919]) and total interstitial inflammation score ( P = .015, RR [95% confidence interval] = 9.662 [1.784–52.329]) were observed to show a negative impact on graft survival. C4d deposition in PTC and glomeruli, the level of pretransplantation sensitization, episodes of acute rejection, and C4d in previous (pre-TG) biopsies did not influence the survival of grafts with TG. Conclusions Younger recipient age and minimal immunosuppression were associated with C4d positivity in grafts with TG. The survival of kidney grafts with TG was significantly affected by the magnitude of inflammation in the interstitium and PTC, but not by C4d positivity in PTC and glomeruli.

Ahmedabad tolerance induction protocol and chronic renal allograft dysfunction: pathologic observations and clinical implications

BackgroundChronic Renal Allograft Dysfunction (CRAD) is responsible for a large number of graft failures. We have abrogated acute T-cell rejections using Ahmedabad Tolerance Induction Protocol (ATIP) with hematopoietic stem cell transplantation (HSCT) under non-myeloablative conditioning pre-transplant. However B-cell mediated rejections and CRAD continue to haunt us. We carried out retrospective analysis of renal allograft biopsies performed in the last 4 years to evaluate the effect of ATIP on CRAD.Materials and methodsBiopsies diagnosed as per modified Banff criteria belonged to 2 groups: ATIP under low dose immunosuppression of cyclosporine/Azathioprine/Mycofenolate mofetil+ Prednisolone, subjected to donor leucocyte transfusion, anti-T/B cell antibodies, low dose target specific irradiation, cyclophosphamide, cyclosporin followed by HSCT pre-transplant; controls who opted out of ATIP were transplanted under standard triple drug immunosuppression. Demographics of both groups were comparable.ResultsIncidence of chronic changes was higher in controls (17.5%) vs. 10.98% in ATIP over a mean follow up of 151.9 months in the former and 130.9 months in the latter. Proteinuria and hypertension were higher in controls (48.4%) vs. ATIP (32.7%) with chronic transplant glomerulopathy, focal global sclerosis in 67.7% in controls vs. 46.7% in ATIP, acute on chronic T/B cell rejection in 51.6% controls vs. 28.1% ATIP, with peritubular capillary C4d deposits in 19.4% controls vs. 1.9% ATIP biopsies. Acute on chronic calcineurin inhibitor toxicity was higher in ATIP (71.9%) vs. 48.4% in controls.ConclusionChronic immune injury was less with ATIP vs controls as compared to a higher incidence of chronic calcineurin inhibitor toxicity in the former.

Clinical significance of the distribution of C4d deposits in different anatomic compartments of the allograft kidney

Diffuse C4d deposition in peritubular capillaries is a well-recognized marker of antibody-mediated rejection. The significance of staining patterns that are focal or affect non-peritubular capillary compartments is less well defined. Paired frozen section and paraffin-embedded tissue stains were performed in 52 kidney allograft biopsies, and correlated with clinicopathologic parameters. Diffuse peritubular capillary C4d deposits were more often seen in frozen sections (22/52, 43% frozen tissue vs 10/52, 19% paraffin-embedded tissue), whereas focal staining was observed more frequently within paraffin sections (13/52, 25% paraffin-embedded tissue vs 7/52, 14% frozen tissue). In biopsies taken from patients with a history of donor-specific antibodies, diffuse, focal and negative peritubular capillary C4d staining patterns were seen in 11/14 (79%), 1/14 (7%) and 2/14 (14%) of frozen biopsies vs 5/14 (36%), 6/14 (43%) and 3/14 (21%) of paraffin-embedded biopsies. Transplant glomerulopathy score in paraffin-embedded biopsies was higher in specimens with vs without glomerular basement membrane C4d staining (1.5±0.8 vs 1.0±0.6, P=0.03). Tubular basement membrane staining was present in 4% paraffin-embedded and 48% frozen specimens independent of tubular atrophy. Arteriolar hyalinosis score in paraffin-embedded specimens was higher in biopsies with vs those without arteriolar C4d deposits (1.3±0.9 vs 0.9±0.8, P=0.04). Arterial staining was unrelated to the degree of intimal thickening. In conclusion, peritubular capillary deposits correlate well with circulating donor-specific antibody. For paraffin-embedded tissue, combining the results of focal and diffuse staining allows a diagnostic sensitivity comparable to diffuse staining in frozen tissue. Finally, C4d deposits preferentially in lesions of chronic transplant glomerulopathy and arteriolar hyalinosis.

Successful Treatment of Chronic Antibody-Mediated Rejection With IVIG and Rituximab in Pediatric Renal Transplant Recipients

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. 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. 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. 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.