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.     

The difference in histopathology of antibody-mediated rejection between ABO incompatible and pre-sensitized cases

Abstract:  Suppression of antibody-mediated rejection (AMR) is mandatory for the acceptance of renal allograft in ABO blood type incompatible and pre-sensitized combinations. The aim of this study was to evaluate the difference in histopathology of AMR between ABO incompatible (ABOI) and pre-sensitized cases. Among 69 kidney recipients who underwent transplant surgery at our institute since 2002, four patients who manifested AMR were included in this study. They initially received quadrant immunosuppressants, tacrolimus, mycophenolate mofetil, methylprednisolone and basiliximab. Two patients received grafts from ABOI donors and the other two received grafts from flow T-cell crossmatch-positive donors. Although satisfying antibody removal was achieved by pre-transplant plasmapheresis, all four cases manifested acute AMR, within two wk post-transplant. Antibody titer and panel reactive antibody increased at the time of AMR. ABOI cases showed slight cellular infiltration. These cases showed diffuse, strong and linear deposition of C4d at peritubular capillaries (PTC). On the other hand, pre-sensitized cases showed more intense cellular infiltration, especially in glomerulus but only faint and focal deposition of C4d at PTC. All four cases were treated with corticosteroid pulse therapy in conjunction with several sessions of plasmapheresis.     

Histologic Findings One Year After Positive Crossmatch or ABO Blood Group Incompatible Living Donor Kidney Transplantation

Recent protocols have allowed successful positive crossmatch (+XM) and ABO incompatible (ABOI) kidney transplantation, although their long-term outcome is not clear. To begin to assess this issue we compared protocol biopsies performed 12 months posttransplant in 37 +XM, 24 ABOI and 198 conventional allografts. Although the majority in all three groups had only minimal histologic changes, transplant glomerulopathy (TG) was significantly increased in +XM (22% vs. 13% ABOI vs. 8% conventional, p = 0.015), and correlated with prior humoral rejection (HR) by multivariate analysis (odds ratio 17.5, p < or = 0.0001). Patients with a prior history of HR also had a significant increase in interstitial fibrosis (No HR 54% vs. HR 86%, p = 0.045). In the absence of HR no difference in histologic changes was seen between groups, although all three groups had a demonstrable mild increase in interstitial fibrosis from biopsies performed at the time of transplant. Thus, although HR is associated with an increase in TG, in its absence allograft histology is similar in +XM, ABOI and conventional allografts 1 year posttransplant.     

C4d and C3d Staining in Biopsies of ABO- and HLA-Incompatible Renal Allografts: Correlation with Histologic Findings

Biopsies of ABO-incompatible and positive crossmatch (HLA-incompatible) renal allografts were retrospectively examined to compare results of C4d and C3d staining, and the correlation between such staining and histologic findings suggestive of antibody-mediated rejection (AMR). A total of 75 biopsies (55 protocol, 17 for graft dysfunction, 3 for other indications) of 24 ABO-incompatible grafts and 244 biopsies (103 protocol, 129 for graft dysfunction, 12 for other indications) of 66 HLA-incompatible grafts were examined; all were stained for C4d and approximately 40% for C3d. In ABO-incompatible grafts, 80% of protocol biopsies and 59% performed for graft dysfunction showed C4d staining in peritubular capillaries (PTC); this staining was not correlated with neutrophil margination in PTC. In HLA-incompatible grafts, PTC C4d was present in 26% of protocol biopsies and 60% of biopsies for graft dysfunction; 92% of biopsies with >1+ (0-4+ scale), diffuse PTC C4d had > or =1+ margination and/or thrombotic microangiopathy (TMA), compared with 12% of C4d-negative biopsies. C3d was somewhat more predictive of margination than C4d in ABO-incompatible, but not HLA-incompatible, grafts. In summary, while PTC C4d deposition indicates probable AMR in biopsies of HLA-incompatible grafts, including protocol biopsies, there is no histologic evidence that C4d deposition is correlated with injury in most ABO-incompatible grafts.     

Characterization of rejection episodes in patients following positive crossmatch and ABO-incompatible live donor renal transplantation

For kidney transplant recipients with donor-specific antibody (DSA) to HLA- (+XM) or ABO-antigens (ABOI), there is a need to improve detection and treatment of antibody-mediated rejection (AMR). The methods included a retrospective review of consecutive patients that received plasmapheresis and immune globulin (PPIVIg) to abrogate +XM or ABOI. Twelve patients were transplanted after PPIVIg (+XM = 9, ABOI = 2, +XM/ABOI = 1). No hyperacute rejections occurred. Rejection occurred in seven patients [four AMR, three acute cellular rejection (ACR)]. In four +XM patients, DSA was detected during graft dysfunction despite lack of histologic and C4d features of AMR. In one patient, DSA preceded the histologic and immunofluorescent features of AMR. In another patient with borderline changes and DSA, graft function improved after PPIVIg, despite lack of histologic or immunofluorescent evidence of AMR. One patient with Banff IIA ACR and DSA treated with antithymocyte antibody but not PPIVIg had recurrent rejections and poor graft function. In +XM and ABOI recipients with graft dysfunction: (i) DSA may represent AMR in the absence of C4d or histologic features of AMR; (ii) DSA can precede C4d or light microscopic features of AMR; (iii) A poor outcome may result if DSA or continued allograft dysfunction is present and not treated despite a negative biopsy.     

Subclinical Acute Antibody-Mediated Rejection in Positive Crossmatch Renal Allografts

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

C4d deposition without rejection correlates with reduced early scarring in ABO-incompatible renal allografts

C4d deposition in peritubular capillaries is a specific marker for the presence of antidonor antibodies in renal transplant recipients and is usually associated with antibody-mediated rejection (AMR) in conventional allografts. In ABO-incompatible grafts, however, peritubular capillary C4d is often present on protocol biopsies lacking histologic features of AMR; the significance of C4d in this setting remains unclear. For addressing this, data from 33 patients who received ABO-incompatible renal allografts (after desensitization) were retrospectively reviewed. Protocol biopsies were performed at 1 and/or 3 and 6 mo after transplantation in each recipient and at 12 mo in 28 recipients. Twenty-one patients (group A) had strong, diffuse peritubular capillary C4d staining without histologic evidence of AMR or cellular rejection on their initial protocol biopsies. The remaining 12 patients (group B) had negative or weak, focal peritubular capillary C4d staining. Three grafts (two in group B) were lost but not as a result of AMR. Excluding these three patients, serum creatinine levels were similar in the two groups at 6 and 12 mo after transplantation and at last follow-up; however, recipients in group A developed significantly fewer overall chronic changes, as scored by the sum of Banff chronic indices, than group B during the first year after transplantation. These results suggest that diffuse peritubular capillary C4d deposition without rejection is associated with a lower risk for scarring in ABO-incompatible renal allografts; the generalizability of these results to conventional allografts remains unknown.     

Acute rejection in non-compliant renal allograft recipients: a distinct morphology

Non-compliance for immunosuppressive medication is frequent in renal transplant recipients, and associated with late acute rejection and graft loss. Although numerous studies were published on risk factors and outcome, no data are available on the histopathology of the 'non-compliant' allograft. As non-compliant patients swing between subtherapeutic and toxic doses of immunosuppression, trough levels show large variation. We questioned whether the histology of acute rejection in non-compliers (i) differs from the 'classical' acute rejection; (ii) shows more concomitant calcineurin-inhibitor toxicity; (iii) is associated with C4d and plasma cell (PC)-rich infiltrates. Based on validated interview methods/self reporting, 145 adult renal allograft recipients, transplanted for greater than one yr, on cyclosporine A and corticosteroids, were categorized as either compliant or non-compliant. Non-compliance was defined in 32 patients (22.1%). All late (greater than one yr) allograft biopsies were reviewed (Banff) and immuno-stained for C4d. Computerized morphometry was performed on late biopsies with features of acute cellular rejection. Sixty-two patients had > or =1 late biopsy [41 (36.2%) compliant/21 (65.6%) non-compliant; p = 0.0043], comprising a pool of 90 biopsies (61 compliant/29 non-compliant; p = 0.0303). 'Non-compliant' biopsies had higher scores of C4d (p = 0.0092), acute tubular damage (p = 0.0058), and peritubular capillaritis (p = 0.0070). 'Non-compliant' biopsies with acute cellular rejection showed less interstitial edema (p = 0.0165), more interstitial infiltrate (p = 0.0100), more interstitial fibrosis (p = 0.0277), and more tubular atrophy (p = 0.0197). PC-rich infiltrates correlated with C4d (p = 0.0080). Detection of non-compliance is mandatory as it represents an important cause of graft loss. This study describes histologic features of renal allograft biopsies in non-compliant patients that could help identifying this patient profile.     

Determinants of Poor Graft Outcome in Patients with Antibody-Mediated Acute Rejection

This study analyzes the incidence and course of antibody-mediated rejection (AMR) in a cohort of 237 renal transplant patients followed for 30 +/- 20 months. Among these, 32 patients were considered to be at risk for AMR and received intravenous immunoglobulin (IVIg), either as preconditioning (Group A, n = 18) or at the time of transplant (Group B, n = 14). The prevalence of AMR was 27.8% in Group A, 57.1% in Group B and 3.9% in the remainder of the population. Although graft loss remains greater among AMR than for acute cellular rejection (ACR) or the overall transplant population, we have identified a good outcome group (GFR > 15 mL/min/1.73 m(2)) (n = 13), whose renal function at the end of follow-up was comparable to that of the general transplant population. The factors associated with bad outcome are: (1) immunologic: presence and/or persistence of donor-specific anti-HLA antibodies post-transplantation and (2) histologic: neutrophilic glomerulitis, peritubular capillary dilatation with neutrophil infiltrates and interstitial edema at the time of first biopsy; and at the time of late biopsy (3-6 months): lesions of vascular rejection, and monocyte/macrophage infiltrates in glomeruli and dilated peritubular capillaries. Persistence of C4d does not predict outcome. This study outlines for the first time the immunologic and histologic profiles of AMR patients with poor prognosis.     

Capillary deposition of complement split product C4d in renal allografts is associated with basement membrane injury in peritubular and glomerular capillaries: a contribution of humoral immunity to chronic allograft rejection

Endothelial deposition of the complement split product C4d is an established marker of antibody-mediated acute renal allograft rejection. A contribution of alloantibody-dependent immune reactions to chronic rejection is under discussion. In this study, the association of immunohistochemically detected endothelial C4d deposition in peritubular capillaries (PTC) with morphologic features of chronic renal allograft injury was investigated in a large study cohort. C4d deposits in PTC were detected in 73 (34%) of 213 late allograft biopsies performed in 213 patients more than 12 mo after transplantation (median, 4.9 yr) because of chronic allograft dysfunction. Endothelial C4d deposition was found to be associated with chronic transplant glomerulopathy (CG) (P < 0.0001), with basement membrane multilayering in PTC (P = 0.01), and with an accumulation of mononuclear inflammatory cells in PTC (P < 0,001). Furthermore, C4d deposits in PTC (in biopsies with normal glomerular morphology) were associated with development of CG in follow-up biopsies. Other morphologic features of chronic allograft nephropathy (with exception of tubular atrophy) were not associated with C4d deposits in PTC. Analyses of previous and follow-up biopsies revealed that C4d deposits may occur de novo and may also disappear at any time after transplantation. In conclusion, the data suggest that complement activation in renal microvasculature, indicating humoral alloreactivity, contributes to chronic rejection characterized by chronic transplant glomerulopathy and basement membrane multilayering in PTC.     

Peritubular Capillaritis in Renal Allografts: Prevalence, Scoring System, Reproducibility and Clinicopathological Correlates

While glomerulitis is graded according to the Banff classification, no criteria for scoring peritubular capillaritis (PTC) have been established. We retrospectively applied PTC-scoring criteria to 688 renal allograft (46 preimplantation, 461 protocol, 181 indication) biopsies.
A total of 26.3% of all analyzed biopsies had peritubular capillaritis (implant 0%, protocol 17.6%, indication 45.5%; p < 0.0001). The most common capillaritis pattern was of moderate severity (5–10 luminal cells), focal in extent (10–50% of PTC), with a minority of neutrophils. A total of 24% of C4d− compared with 75% of C4d+ biopsies showed capillaritis (p < 0.0001). More than 80% of biopsies with glomerulitis had peritubular capillaritis. A total of 50.4% of biopsies with borderline or T-cell mediated rejection (TCMR) and 14.1% of biopsies without TCMR or antibody-mediated rejection (ABMR) showed capillaritis (p < 0.0001). The inter-observer reproducibility of the PTC-scoring features was fair to moderate. Diffuse capillaritis detected in early protocol biopsies had significant negative prognostic impact in terms of glomerular filtration rate 2 years posttransplantation. Indication biopsies show a significantly higher prevalence of capillaritis than protocol biopsies (45.5% vs. 17.6%; p < 0.0001). Capillaritis is more frequent and pronounced in ABMR, but can be observed in TCMR cases. Thus, scoring of peritubular capillaritis is feasible and can provide prognostic and diagnostic information in renal allograft biopsies.     

Presentation and Outcomes of C4d‐Negative Antibody‐Mediated Rejection After Kidney Transplantation

The updated Banff classification allows for the diagnosis of antibody‐mediated rejection (AMR) in the absence of peritubular capillary C4d staining. Our objective was to quantify allograft loss risk in patients with consistently C4d‐negative AMR (n = 51) compared with C4d‐positive AMR patients (n = 156) and matched control subjects without AMR. All first‐year posttransplant biopsy results from January 2004 through June 2014 were reviewed and correlated with the presence of donor‐specific antibody (DSA). C4d‐negative AMR patients were not different from C4d‐positive AMR patients on any baseline characteristics, including immunologic risk factors (panel reactive antibody, prior transplant, HLA mismatch, donor type, DSA class, and anti‐HLA/ABO‐incompatibility). C4d‐positive AMR patients were significantly more likely to have a clinical presentation (85.3% vs. 54.9%, p < 0.001), and those patients presented substantially earlier posttransplantation (median 14 [interquartile range 8–32] days vs. 46 [interquartile range 20–191], p < 0.001) and were three times more common (7.8% vs 2.5%). One‐ and 2‐year post–AMR‐defining biopsy graft survival in C4d‐negative AMR patients was 93.4% and 90.2% versus 86.8% and 82.6% in C4d‐positive AMR patients, respectively (p = 0.4). C4d‐negative AMR was associated with a 2.56‐fold (95% confidence interval, 1.08–6.05, p = 0.033) increased risk of graft loss compared with AMR‐free matched controls. No clinical characteristics were identified that reliably distinguished C4d‐negative from C4d‐positive AMR. However, both phenotypes are associated with increased graft loss and thus warrant consideration for intervention.     

Therapy Modalities for Antibody Mediated Rejection in Renal Transplant Patients

Introduction: The aim of our study was to determine the effectiveness of immunoglobulin, rituximab and plasmapheresis in renal transplant patients with antibody mediated rejection (AMR). Patients and Methods: Fourteen renal transplant patients with AMR were included in this study. The mean age of the patients was 33.9 ± 10.3 years and 10 (71.4%) of them were male. Lymphocyte cross match was negative for all patients and 10 (71.4%) of them were living donor transplants. Six patients were administered tacrolimus, three patients cyclosporine, two patients everolimus, and three patients sirolimus for immunosuppression. The patients with AMR were administered IVIG, rituximab and plasmapheresis. Results: Patient survival rate was 100%, graft survival rate after AMR was 50% in the first year and 33% in the 2nd and third years. AMR developed 31.9 ± 25.9 months after transplantation. Seven (50%) patients lost their grafts. Delayed graft function was observed in 28.6%, chronic allograft dysfunction in 78.5%, diabetes after transplantation in 14.3%, and cytomegalovirus infection in 7.1% of the patients. At the last follow-up, the mean blood creatinine was 3.1 ± 1.4, the mean proteinuria was 2300 (1300–3300) mg/day and the mean GFR was 34.5 ± 17.6 ml/min. C4d was positive in peritubullar capillaries in all patients, while neutrophil accumulation in peritubular and glomerular capillaries was observed in 8 patients. Chronic allograft vasculopathy was observed in 12 patients. Conclusion: AMR leads to progressive loss of renal function and has low graft survival. More effective treatment alternatives are needed for this clinical issue.     

Expression of TGFbeta-1 and Type I TGFbeta-receptor on sequential biopsies of renal transplants with chronic allograft nephropathy

The aim of this study was to determine the expression of transforming growth factor-beta (TGFbeta)-1 and type I TGFbeta-receptor on sequential biopsies from renal transplants with and without chronic allograft nephropathy. Twenty-four renal transplant recipients entered the study. They underwent sequential biopsies performed before (T1: 1.44 +/- 1.2 months) and 6 months after (T2: 15.96 +/- 7.2 months) transplantation. Lesions were graded according to the criteria of the Banff classification. C4d was detected by fluorescence microscopy. Immunohistochemistry was performed in order to identify cells expressing TGFbeta-1 and type I TGFbeta-receptor. In normal renal tissue (n = 4), TGFbeta-1 is expressed by tubular epithelial cells and endothelial cells lining glomerular and peritubular capillaries, whereas type 1 TGFbeta-receptor is expressed by tubular epithelial cells and smooth muscle cells in the media of arteries. In recipients with chronic allograft nephropathy (group 1, n = 14), diffuse epithelial expression of both molecules was found in more patients at T2 than at T1 (42.8% vs 21.4%). In contrast, this pattern of expression remained stable or decreased over time in recipients with long-term normal transplants (group 2, n = 10). Furthermore, type 1 TGFbeta-receptor was detected on the smooth muscle cells of arteries in 12/14 (85.7%) of recipients in group 1 and only in 4/9 (44.4%) of recipients in group 2. No relationship was noticed with regard to C4d deposits. These data suggest that the synthesis of TGFbeta-1 and type I TGFbeta-receptor increases over time in recipients developing chronic allograft nephropathy. Further studies are in progress in order to quantify mRNA of both molecules with real-time polymerase chain reaction.     

C4D deposition and positive posttransplant crossmatch are not necessarily markers of antibody-mediated rejection in renal allograft recipients

The aim of the study was to search for serologic, immunopathologic, and morphologic evidence of antibody-mediated rejection (AMR) among patients with acute renal allograft dysfunction. The study included 19 patients with episodes of acute rejection (ARE) within the first year after transplantation. All patients had negative crossmatch tests before transplantation. Patients underwent biopsy for histologic and C4d examinations. All patients were monitored for donor-specific HLA alloantibodies during the first posttransplant year. Complement-dependent cytotoxic crossmatches were performed with donor lymphocytes. In eight patients, the crossmatch test results changed to positive during ARE. In all biopsies except one with cortical infarction, we observed C4d staining (group 1). The biopsies of four patients showed histologic changes of AMR, and all of their grafts were lost. In one patient, cellular and vascular rejection (Banff II) were present; in two, Banff I; and in one, borderline lesions. These results were compared with 11 patients with ARE but negative posttransplant crossmatches and negative staining for C4d (group 2). The histologic findings in the biopsies of these patients were cellular interstitial and vascular rejection (Banff I and Banff II). With no features suggestive of AMR. During the first year after transplantation, the creatinine levels of group 1 patients, were significantly higher than group 2 patients. One-year graft survival was 50% in group 1 and 91% in group 2. CONCLUSIONS: C4d and a positive posttransplant crossmatch were not associated with histologic features of AMR in half of the ARE. Nevertheless, C4d deposition and positive posttransplant crossmatches correlated with allograft injury among renal transplant patients.     

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

The complement activation demonstrated by vascular C4d deposition is used to diagnose antibody-mediated rejection (AMR) in renal allografts, but remains controversial in lung transplantation (LTX). METHODS: C4d deposition was assessed by immunohistochemistry in 192 lung transplant biopsies from 32 patients. ELISA analysis was performed on 415 serum samples in those 32 temporally and rejection-grade matched LTX patients; 16 patients developed HLA-Ab, while the other 16 patients remained negative. The specificity of C4d staining was further compared in 18 additional LTX patients without HLA-Ab or acute cellular rejection (ACR), but in the presence of CMV-pneumonitis or reperfusion injury. RESULTS: Specific subendothelial C4d deposition was seen in 5 of 16 (31%) patients with HLA-Ab and was absent in 16 patients without HLA-Ab (p<0.05). All patients with specific C4d deposition exhibited donor-specific HLA-Ab. There were 13 patients with bronchiolitis obliterans syndrome in the group of 16 HLA-Ab positive patients, versus 2/16 in ELISA-negative patients (p<0.005). One of 7 patients with CMV pneumonitis and 2 of 11 patients with reperfusion injury also showed C4d positivity (not statistically significant). CONCLUSIONS: In this study, specific subendothelial C4d deposition was a marker for the involvement of HLA-Ab in lung allograft rejection. The patchy nature, low sensitivity, and specificity of C4d staining might limit clinical use in protocol biopsies. However, in patients with decreasing pulmonary function, refractory ACR and/or HLA-Ab, specific C4d deposition may serve as a marker of coexistent AMR.     

The impact of C4d and microvascular inflammation before we knew them

It is important to identify prognostically important morphologic criteria in post‐transplant management to tailor therapy and improve outcomes. Therefore, using biopsies carried out for cause <1‐yr post‐transplant, from an era when C4d staining and microvascular inflammation (MVI) were not clinically utilized, we studied the importance of C4d and MVI on graft survival. Snap‐frozen first renal allograft biopsy specimens (done for cause) in the first post‐transplant year from 1996 to 2001 were stained/examined for C4d, and pathology re‐examined by a separate blinded pathologist. Graft outcomes in patients with and without MVI and/or C4d were compared. Of 128 patients, 39 (30.5%) biopsies were C4d+ and 89 (69.5%) were C4d?; 67 (52.3%) had no MVI (MVI?) while 61 (47.7%) had glomerulitis, peritubular capillaritis, or both (MVI+). There were no significant demographic differences between MVI+ and MVI? patients. A greater proportion of C4d+ biopsies was MVI+ (67%) than MVI? (33%; p = 0.004). C4d positivity had no impact on death‐censored graft survival (DCGS). In contrast DCGS was worse in MVI+ than MVI? regardless of presence/absence of C4d (p = 0.005). In biopsies for cause carried out <1‐yr post‐transplant, MVI is associated with decreased DCGS, independent of the presence of C4d.     

C4d peritubular capillary staining in chronic allograft nephropathy and transplant glomerulopathy: an uncommon finding

The true incidence of positive C4d staining in the peritubular capillaries of biopsies with chronic allograft nephropathy (CAN) and transplant glomerulopathy (TGP) remains controversial. We retrospectively reviewed all transplant biopsies performed at Saint Louis University Hospital between June 2002 and May 2004. We examined the incidence of positive C4d staining in the peritubular capillaries of biopsy specimens with pure CAN with or without features of TGP. We identified 54 biopsies in 43 patients showing CAN. The average age was 46 ± 13 years. The average creatinine at the time of biopsy was 308 ± 211 μmol/l (3.5 ± 2.4 mg/dl). Twenty (37%) biopsies exhibited features consistent with TGP. Only two biopsies had positive C4d staining in the peritubular capillaries. The C4d positive biopsies were from two different patients; one patient had donor specific antibodies (DSA) against HLA class 1 at the time of biopsy and the other patient had no detectable DSA. None of the TGP biopsies showed peritubular C4d staining. C4d staining of the peritubular capillaries appears to be rare in patients with pure CAN with and without TGP features.     

Antibody-Mediated Rejection of a Pancreas Allograft

The role of antibody-mediated rejection (AMR) in pancreas transplantation is poorly understood. Here, we report on a patient who developed AMR of his pancreas allograft after receiving a simultaneous pancreas-kidney transplant. Pre-operative enhanced cytotoxicity and flow cytometry T-cell crossmatches were negative; B-cell crossmatches were not performed as per institutional protocol. The patient's post-operative course was significant for elevated serum amylase levels and development of hyperglycemia approximately 1 month after transplantation. A pancreatic biopsy at this time showed no cellular infiltrate but strong immunofluorescent staining for C4d in the interacinar capillaries. Analysis of the patient's serum identified donor-specific HLA-DR alloantibodies. He received intravenous immunoglobulin (IVIg), rituximab and plasmapheresis, and his pancreatic function normalized. We conclude that clinically significant AMR can develop in a pancreas allograft and recommend that pancreatic biopsies be assessed for C4d deposition if the patient has risk factors for AMR and/or the pathologic evidence for cell-mediated rejection is underwhelming.