Cohort study of the prognostic significance of acute transplant glomerulitis in acutely rejecting renal allografts

Rate, Factors, and Outcome of Delayed Graft Function After Kidney Transplantation of Deceased Donors

BACKGROUND

Delayed graft function (DGF) is a frequent complication after kidney transplantation affecting long-term outcome.

PATIENTS AND METHODS

A total of 525 consecutive recipients (age 54.2 ± 13.4 years, 33% female) of kidneys from deceased donors transplanted between 2005 and 2012 were retrospectively examined. DGF was defined as the need of dialysis within the first week after transplantation.

RESULTS

DGF developed in 21.1% (n = 111). Factors associated with DGF (P ≤ .035, respectively) were recipient body mass index, C-reactive protein of the recipient, residual diuresis, cold ischemia time, donor age, and diuresis in the first hour after transplantation. Median duration of DGF was 16 (2-66) days. Patients after DGF had a significantly lower GFR compared with recipients without DGF either after 3 (32.9 ± 16.5 vs 46.3 ± 18.4 mL/min/1.73 m²) or after 12 months (38.9 ± 19.3 vs 48.6 ± 20.4 mL/min/1.73 m², P < .001, resp.). During DGF, 12.4% developed BANFF II and 18.0% BANFF I rejection, 20.2% had signs of transplant glomerulitis (first biopsy), and 16.2% (n = 18) remained on dialysis.

CONCLUSION

DGF affects 1 out of 5 kidney transplants from deceased donors. Minimizing modifiable risk factors, in particular immunologic risk, may ameliorate the incidence and outcome of DGF. The outcome of DGF depends mainly on the diagnosis of any rejection and worsens upon detection of transplant glomerulitis and pronounced interstitial fibrosis and tubular atrophy (IFTA).

Infiltration of Macrophages Correlates with Severity of Allograft Rejection and Outcome in Human Kidney Transplantation

OBJECTIVE

Despite substantial progress in recent years, graft survival beyond the first year still requires improvement. Since modern immunosuppression addresses mainly T-cell activation and proliferation, we studied macrophage infiltration into the allografts of 103 kidney transplant recipients during acute antibody and T-cell mediated rejection. Macrophage infiltration was correlated with both graft function and graft survival until month 36 after transplantation.

RESULTS

Macrophage infiltration was significantly elevated in antibody-mediated and T-cell mediated rejection, but not in kidneys with established IFTA. Treatment of rejection with steroids was less successful in patients with more prominent macrophage infiltration into the allografts. Macrophage infiltration was accompanied by increased cell proliferation as well as antigen presentation. With regard to the compartmental distribution severity of T-cell-mediated rejection was correlated to the amount of CD68+ cells especially in the peritubular and perivascular compartment, whereas biopsies with ABMR showed mainly peritubular CD68 infiltration. Furthermore, severity of macrophage infiltration was a valid predictor of resulting creatinine values two weeks as well as two and three years after renal transplantation as illustrated by multivariate analysis. Additionally performed ROC curve analysis showed that magnitude of macrophage infiltration (below vs. above the median) was a valid predictor for the necessity to restart dialysis. Having additionally stratified biopsies in accordance to the magnitude of macrophage infiltration, differential CD68+ cell infiltration was reflected by striking differences in overall graft survival.

CONCLUSION

The differences in acute allograft rejection have not only been reflected by different magnitudes of macrophage infiltration, but also by compartment-specific infiltration pattern and subsequent impact on resulting allograft function as well as need for dialysis initiation. There is a robust relationship between macrophage infiltration, accompanying antigen-presentation and resulting allograft function.

Emerging Concepts and Controversies in Renal Pathology: C4d-Negative and Arterial Lesions as Manifestations of Antibody-Mediated Transplant Rejection

The consensus classification of antibody-mediated rejection (AMR) of renal allografts developed at the Sixth Banff Conference on Allograft Pathology, in 2001, identified three findings necessary for the diagnosis of active AMR: histologic evidence, antibodies against the graft, and capillary C4d deposition. Morphologic and molecular studies have noted evidence of microvascular injury, which, in the presence of donor-specific antibodies (DSAs) but the absence of C4d deposition, is associated with development of transplant glomerulopathy and graft loss. Recent studies suggest that intimal arteritis may in some cases be a manifestation of DSA-induced graft injury. These newly recognized lesions of AMR have now been incorporated into a revised Banff diagnostic schema.

Glomerular inflammation correlates with endothelial injury and with IL-6 and IL-1β secretion in the peripheral blood

BACKGROUND

Transplant glomerulitis is an active form of glomerular injury associated with suboptimal graft outcome, inadequate histologic reproducibility, and poorly understood pathogenesis. Using a modified pathologic schema where glomerular inflammation is defined by the presence of five or more leukocytes per glomerulus, we sought to assess the reproducibility of transplant glomerulitis and to prospectively investigate the pathogenesis of glomerular inflammation.

METHODS

Our cohort includes 59 kidney transplant recipients who underwent 60 "for cause" allograft biopsies. In addition to light microscopy, the majority of the biopsies were assessed using immunohistochemistry, immunofluorescence, and electron microscopy studies. Biopsies were classified as noninflamed (n=21), inflamed (borderline changes or above) without glomerulitis (n=21), and transplant glomerulitis (n=18). Peripheral blood was collected on the day of biopsy and cytokines secreted by peripheral blood mononuclear cells (PBMCs) were measured ex vivo.

RESULTS

Our modified schema had higher inter-observer agreement for detecting glomerulitis than that of the current Banff schema. Biopsies with glomerulitis showed ultrastructural signs of glomerular capillary wall remodeling. In contrast to other anatomic compartments, intraglomerular leukocytes in glomerulitis group consisted largely of monocytes. Patients with glomerulitis had high levels of IL-6 and IL-1β secreted by PBMCs. Furthermore, the percentage of inflamed glomeruli and the number of intraglomerular monocytes showed independent association with IL-6 and IL-1β levels, which tended to correlate with subsequent estimated glomerular filtration rate decline.

CONCLUSIONS

Inter-observer reproducibility of transplant glomerulitis can be improved by using more stringent histologic criteria. Glomerular inflammation correlates with endothelial injury, monocyte influx, and IL-6 and IL-β secretion by circulating immune cells.

An updated Banff schema for diagnosis of antibody-mediated rejection in renal allografts

PURPOSE OF REVIEW

To introduce the updated Banff schema for antibody-mediated renal allograft rejection and related revisions to definitions within this schema agreed upon during and immediately subsequent to the 2013 Banff Conference on Allograft Pathology.

RECENT FINDINGS

The original Banff schema for diagnosis of acute and chronic, active antibody-mediated rejection (ABMR) in renal allografts, formulated at the 2001 and 2007 Banff Conferences, has been of great assistance to pathologists and clinicians faced with an increasing awareness of the role of donor-specific alloantibodies (DSAs) in producing graft injury. This schema requires histologic (primarily microvascular inflammation and transplant glomerulopathy), immunohistologic (C4d in peritubular capillaries), and serologic (circulating DSA) evidence for a definitive diagnosis of ABMR. Still, like other Banff classifications, the 2001/2007 schema for renal ABMR is a working classification subject to revision based on new data. Increasing evidence for C4d-negative ABMR and antibody-mediated arterial lesions led to the development of a consensus at the 2013 Banff Conference for updating the schema to include these lesions. Definitions and thresholds for glomerulitis and chronic glomerulopathy were also revised to improve interobserver agreement and correlation with clinical, molecular, and serologic data.

SUMMARY

From a consensus reached at the 2013 Banff Conference, an updated schema for diagnosis of acute/active and chronic, active ABMR has been developed that accounts for recent data supporting the existence of C4d-negative ABMR and antibody-mediated intimal arteritis.

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.

Acute transplant glomerulopathy with monocyte rich infiltrate

Acute transplant glomerulopathy refers to alloimmune mediated endothelial injury and glomerular inflammation that typically occurs early post-kidney transplantation. We report a case of a 48-year old woman with end stage renal disease from lupus nephritis who developed an unexplained rise in serum creatinine 2 months after renal transplant. As immunosuppression, she received alemtuzumab induction followed by a tacrolimus, mycophenolate mofetil and prednisone maintenance regimen. Her biopsy revealed severe glomerular endothelial injury associated with monocyte/macrophage-rich infiltrate in addition to mild acute tubulointerstitial cellular rejection. We briefly discuss acute transplant glomerulitis, its pathology and association with chronic/overt transplant glomerulopathy, C4d negative antibody-mediated rejection and the significance of monocytes in rejection. We also postulate that alemtuzumab induction may have contributed to the unusual pattern of monocyte-rich transplant glomerulitis.

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.

Pathologic features of antibody-mediated rejection in renal allografts: an expanding spectrum

PURPOSE OF REVIEW

This review discusses recent findings that are changing and expanding the spectrum of pathologic changes associated with antibodies directed against renal allografts.

RECENT FINDINGS

This review focuses on four lesions: subclinical antibody-mediated rejection (AMR), C4d-negative AMR, intimal arteritis, and arterial intimal fibrosis. A number of studies have identified morphologic lesions of AMR in protocol biopsies of normally functioning renal allografts, particularly in sensitized recipients, that correlate with subsequent development of chronic changes in the graft, including transplant glomerulopathy. These same studies as well as molecular studies of indication biopsies of conventional renal allografts have noted evidence of microvascular injury, which, in the presence of donor-specific antibodies (DSAs) but the absence of C4d deposition in peritubular capillaries, is associated with development of transplant glomerulopathy and graft loss. Finally, recent studies suggest that intimal arteritis, previously felt to represent a lesion of cell-mediated rejection, and bland arterial intimal fibrosis, resembling arteriosclerosis, may in some cases be manifestations of DSA-induced graft injury.

SUMMARY

Incorporation of these newly recognized lesions of AMR into a working diagnostic schema with sufficient sensitivity and specificity to minimize undertreatment and overtreatment of patients is an important challenge currently faced by renal pathologists and transplant clinicians.

A new diagnostic algorithm for antibody-mediated microcirculation inflammation in kidney transplants

We studied the significance of microcirculation inflammation in kidney transplants, including 329 indication biopsies from 251 renal allograft recipients, who were mostly nonpresensitized (crossmatch negative). Glomerulitis (g) and peritubular capillaritis (ptc) were often associated with antibody-mediated rejection (65% and 75%, respectively), but were also found in other diseases in the absence of donor-specific antibody (DSA): T-cell-mediated rejection (ptc, g), glomerulonephritis (g) and acute tubular necrosis (ptc). To develop rules for reducing the nonspecificity of microcirculation inflammation and defining the best grading thresholds associated with DSA, we built and validated a decision tree to predict DSA. The decision tree revealed that g + ptc sum (addition of g-score plus ptc-score) was the best predictor of DSA, followed by time posttransplant, then C4d, which had a small role. Late biopsies with g + ptc > 0 showed higher frequency of DSA compared to early biopsies with g + ptc > 0 (79% vs. 27%). Microcirculation inflammation in early biopsies was often false positive (antibody-independent). The decision tree predicted DSA with higher sensitivity and accuracy than C4d staining. Microcirculation inflammation sum score predicted graft failure independently of time, C4d and transplant glomerulopathy. Thus any degree of microcirculation inflammation in late kidney transplant biopsies strongly indicates presence of DSA and predicts progression to graft failure.

Glomerulitis during acute cellular rejection may be a surrogate marker of vasculitis in renal allografts--better index for diagnosis of vasculitis

BACKGROUND

The Banff criteria (from 2005 to 2009) use "T cell-mediated rejection" to indicate acute cellular rejection. Vasculitis in smaller arteries is an important diagnostic criterion for moderate and severe T cell-mediated rejection. The renal allograft endothelium is a significant target of inflammatory response-mediated tissue damage. Medium-size arteries (arcuate arteries) are mostly absent in routine allograft biopsies, so identification of vasculitis relies on its identification in small arteries (arterioles to interlobar arteries). Although inflammation in terminal vessels such as the glomerular capillaries has been previously recognized, their role in grading the rejection process is not well characterized. We therefore evaluated the expression of CD3-positive T lymphocytes and CD68-positive macrophages in glomeruli, small arteries, and arcuate arteries of nephrectomy specimens obtained from transplant and renal tumor patients.

METHODS

The study group included 21 renal explant subjects with nonreversible moderate to severe T cell-mediated rejection (IIa to III) and/or severe chronic changes. The control group comprised 17 individuals with nephrectomy for renal tumors. In each case, a large renal section from cortex to medulla was stained for CD3 and CD68 by immunohistochemical method. CD3-positive T lymphocytes and CD68-positive macrophages per balanced high-power field were counted in glomeruli, interlobar arteries, and arcuate arteries.

RESULTS

In control kidney sections, neither CD3-positive T lymphocytes nor CD68-positive macrophages were noted in glomeruli, interlobar arteries, or arcuate arteries. In the study group, 15/21 showed diffuse C4d positivity. Also in the study group, positive CD3 and CD68 counts in glomeruli were significantly correlated to both interlobar and arcuate artery counts by linear regression analysis.

CONCLUSION

We conclude that in renal allograft biopsies, T lymphocytes and macrophages in the glomeruli not only represent a separate entity, "transplant glomerulitis," but also may be a surrogate marker of vasculitis present in larger vascular beds. Comparable amounts of T cells and macrophages imply that "acute cellular rejection" may be a better terminology to reflect the true inflammatory status.

A critical appraisal of methods to grade transplant glomerulitis in renal allograft biopsies

Transplant glomerulitis is an increasingly recognized lesion in renal transplant biopsies. To develop a refined grading system, we defined glomerulitis by the presence of ≥5 leukocytes/glomerulus and evaluated 111 biopsies using three different grading systems: (i) percentage of glomerular involvement, (ii) peak inflammation in the most severely affected glomerulus and (iii) presence/absence of endocapillary occlusion by inflammatory cells. Endocapillary occlusion had no impact on graft survival, but was associated with increased serum creatinine, proteinuria and subsequent transplant glomerulopathy. Grading based on either percent or peak glomerular involvement correlated with graft failure and peritubular capillaritis. However, the percent glomerular involvement method had the additional advantage of displaying associations with: concurrent proteinuria, focal or diffuse immunoperoxidase peritubular capillary C4d staining, 1-year postbiopsy serum creatinine, subsequent detection of donor-specific antibody and development of transplant glomerulopathy. Patients with >75% glomerular involvement also revealed persistent high-grade glomerulitis on follow-up biopsies despite antirejection treatment. In conclusion, grading of glomerulitis is a meaningful exercise, and a quantification system based on percentage of glomerular involvement shows the most robust associations with clinical parameters and prognosis.

Cluster analysis of lesions in nonselected kidney transplant biopsies: microcirculation changes, tubulointerstitial inflammation and scarring

Banff classification empirically established scoring of histologic lesions, but the relationships of lesions to each other and to underlying biologic processes remain unclear. We hypothesized that class discovery tools would reveal new relationships between individual lesions, and relate lesions to C4d staining, anti-HLA donor-specific antibody (DSA) and time posttransplant. We studied 234 nonselected renal allograft biopsies for clinical indications from 173 patients. Silhouette plotting and principal component analysis revealed three groups of lesions: microcirculation changes, including inflammation (glomerulitis, capillaritis) and deterioration (double contours, mesangial expansion); scarring/hyalinosis; and tubulointerstitial inflammation. DSA and C4d grouped with microcirculation inflammation, whereas time posttransplant grouped with scarring/hyalinosis lesions. Intimal arteritis clustered with DSA, C4d and microcirculation inflammation, but also showed correlations with tubulitis. Fibrous intimal thickening in arteries clustered with scarring/hyalinosis. Capillary basement membrane multilayering showed intermediary relationships between microcirculation deterioration and time-dependent scarring. Correlation analysis and hierarchical clustering confirmed the lesion relationships. Thus, we propose that the pathologic lesions in biopsies are not independent but are members of groups that represent distinct pathogenic forces: microcirculation changes, reflecting the stress of DSA; scarring, hyalinosis and arterial fibrosis, reflecting the cumulative burden of injury over time; and tubulointerstitial inflammation. Interpretation of lesions should reflect these associations.

Up-regulation of cyclooxygenase-2 in different grades of acute human renal allograft rejection

BACKGROUND

Cyclooxygenase-2 (COX-2) is up-regulated by a variety of stimuli that are associated with tissue injury and inflammation.

METHODS

The purpose of this study was to analyze COX-2 detection during different grades of acute human renal allograft rejection. COX-2 expressions were analyzed by immunohistochemistry in 74 samples obtained from biopsies with acute rejection of different grades (n= 48), tubular changes (n=13) and from kidney allografts with stable function (n=13).

RESULTS

In interstitial area, there was a significant correlation of COX-2 induction in acute rejection in comparison to tubular changes (1.67 vs. 0.76, p=0.02) and stable function (vs. 0.07, p<0.001), as well as in vessels in the group with acute rejection in relation to stable function (1.1 vs. 0, p=0.04). When the group with acute rejection was analyzed in subgroups, there was a clear increase of COX-2 expression from acute rejection grade IB to III in vessels, in inflammatory infiltrating cells in interstitial area and in glomeruli, while borderline and IA grades were intermediate.

CONCLUSION

COX-2 is up-regulated during acute human renal allograft rejection according to the severity of acute rejection and could be used as a marker of inflammation in kidney transplantation.

The cellular lesion of humoral rejection: predominant recruitment of monocytes to peritubular and glomerular capillaries

Accumulation of inflammatory cells within capillaries is a common morphologic feature of humoral renal allograft rejection and is most easily appreciated if it occurs in glomeruli. The aim of our study was to determine the amount and composition of immune cells within glomeruli and peritubular capillaries (PTC) in cellular and humoral allograft rejection. Immunofluorescent double-labeling for CD31 and CD3 or CD68 was used for phenotyping and enumerating immune cells within glomeruli and PTC. The major findings are: (1) accumulation of immune cells in PTC is far more common than it would be anticipated based on the assessment by conventional histology; (2) it is not the absolute number of immune cells accumulating within capillaries, but rather the composition of the intracapillary cell population that distinguishes humoral rejection from cellular rejection and (3) in C4d positive biopsies a predominantly monocytic cell population accumulates not only within glomeruli but also within PTC. The median value of monocyte/T-cell ratio within PTC was 2.3 in C4d positive biopsies but only 1 (p = 0.0008) in C4d negative biopsies. Given their prominent presence within capillaries and their extensive biological versatility monocytes might contribute to the capillary damage observed in acute and chronic allograft rejection.

Antibody-mediated rejection in renal allografts: lessons from pathology

The past 15 years have seen major advances in the understanding of the effects of anti-donor antibodies on renal allografts at various stages after transplantation. These advances have been due in large part to pathologic examination of both early and late renal allograft biopsies, including both routine histologic evaluation and immunohistology to detect complement split products. As pathologists have become increasingly adept at diagnosing antibody-mediated rejection (AMR) on allograft biopsies, substantial progress has been made in the treatment of AMR and in successful renal transplantation in recipients with pre-existing antibodies against donor blood group (ABO) and/or major histocompatibility (HLA) antigens. This article reviews the pathologic features of hyperacute, acute, and chronic AMR, including some newer findings impacting diagnosis and outcomes, and differences in the implications of similar pathologic findings in ABO- versus HLA-incompatible renal allografts.

Predictive Value of Banff Score of Early Kidney Allograft Biopsies for 1-Year Graft Survival

The aim of this study was to evaluate the Banff score of early kidney allograft biopsies, taken during the first month after transplantation, seeking an association between early rejection and acute tubular necrosis. We analyzed data from 71 patients transplanted between 2000 and 2004 who had renal allograft biopsies performed within the first posttransplant month (23 women, 48 men), ages 18 to 67 years. All biopsies performed in cases of delayed or deteriorated graft function were graded according to the Banff' 97 classification. Twelve months after transplantation, 19 patients exhibited excellent renal function (group 1, serum creatinine concentration [Scr] < or = 1.5 mg/dL); 25 patients demonstrated preserved renal function (group II, Scr 1.51-1.99 mg/dL); and 19 patients showed deteriorated renal function (group III, Scr > or = 2.0 mg/dL). Eight recipients lost their grafts within 1 year after transplantation (group IV). The Banff index was defined as a sum of all components (value of glomerulitis ["g"] + interstitial inflammation ["i"] + tubulitis ["t"] + arteriolar hyaline thickening ["ah"] + intimal arteritis ["v"]). The deterioration of renal function was associated with a higher Banff index; patients who lost their grafts showed the highest values of this index. Scores of "v," "ah," and Banff index were positively correlated with serum creatinine concentrations at 28, 90, 180, and 360 days (P < .05). Glomerulitis ("g") was correlated with creatinine concentrations at 90 and 360 days (P < .05). Tubulitis ("t") and interstitial inflammation ("i") displayed no association with renal function at any time.

Infiltrating Cell Types in Transplant Glomerulitis: Relationship to Peritubular Capillary C4d Deposition

BACKGROUND

Transplant glomerulitis may be part of the acute rejection process in some transplant recipients. Glomerular monocytes have been shown to be the predominant cell type in transplant glomerulitis associated with peritubular capillary C4d deposition. Whether this applies to peritubular capillary C4d-negative (C4d-) biopsy specimens with transplant glomerulitis is unknown.

METHODS

Forty-two biopsy specimens with acute rejection and transplant glomerulitis were immunostained for monocytes, T cells, and C4d. In each biopsy specimen, glomerular monocytes and T cells were counted, and mean numbers of monocytes per glomerulus and T cells per glomerulus were determined.

RESULTS

Peritubular capillary C4d staining was present in 20 biopsy specimens (C4d-positive [C4d+] group) and negative in 22 specimens (C4d- group). There was no significant difference between mean Banff 97 glomerular scores for the 2 groups (C4d+ , 1.60 +/- 0.80; C4d- , 1.77 +/- 0.90). Although the C4d+ group showed a significantly higher mean number of monocytes per glomerulus (3.01 +/- 2.35) than the C4d- group (0.95 +/- 1.00; P < 0.0001), the C4d- group showed a significantly higher mean number of T cells per glomerulus (4.05 +/- 3.05) than the C4d+ group (1.36 +/- 1.24; P = 0.0007). There were proportionately more C4d+ biopsy specimens with a monocyte-T-cell ratio greater than 1.0 (75%) than C4d- specimens (14%; P < 0.0001). Mean glomerular monocyte-T-cell ratio was 3.66 +/- 4.24 for the C4d+ group and 0.39 +/- 0.54 for the C4d- group; the difference was significant (P = 0.0009).

CONCLUSION

In acute rejection with no peritubular capillary C4d deposition, the predominant infiltrating endocapillary cell in transplant glomerulitis is the T cell, unlike acute rejection with peritubular capillary C4d deposition, in which the predominant infiltrating glomerular cell is the monocyte.

Allograft Glomerulitis: Histologic Characteristics to Detect Chronic Humoral Rejection

The aim of this study was to clarify the histopathologic significance of allograft glomerulitis in chronic allograft nephropathy (CAN). Review of our renal allograft biopsy files revealed 140 specimens with CAN among 115 selected patients. They were classified into two groups: one had CAN with glomerulitis (group G), and the other was free of this finding (group NG). We evaluated the clinicopathologic parameters as follows: levels of serum creatinine and proteinuria in the biopsy; presence of circulating anti-donor antibodies; allograft failure rate; history of biopsy-proven acute cellular rejection (ACR) and acute humoral rejection (AHR); complications of ACR and chronic rejection (CR); and results of immunofluorescence studies for C4d and HLA-DR. The glomerulitis group showed a significantly greater incidence of CR complications, the presence of circulating anti-donor antibodies, and C4d deposition in peritubular and glomerular capillaries. This group also showed higher levels of serum creatinine and proteinuria, higher graft loss rate, and increased AHR incidence, although the differences were not significant. There was also no statistical significance in the HLA-DR expression on tubular epithelial cells. The present results strongly suggest that humoral factors may play an important role in the progression of glomerulitis in CAN. Therefore, we suspect that glomerulitis in CAN is one of the main histologic markers for CR. The presence of glomerulitis may represent humoral factor-dependent inflammation. It should be considered an important diagnostic criterion for CR in addition to double-contour formation and elastica disruptions with or without subendothelial inflammation (Banff '97).

Immunologic risk factors and glomerular C4d deposits in chronic transplant glomerulopathy

BACKGROUND

Chronic transplant glomerulopathy is an uncommon cause of chronic transplant dysfunction of unknown pathogenesis. We evaluated the epidemiologic, clinical, and histologic features of chronic transplant glomerulopathy. To determine the possible contribution of humoral immune responses, we assessed glomerular deposition of C4d.

METHODS

From a cohort of 1111 kidney transplants (1983 to 2001) with at least 6 months of graft function, we identified 18 cases with chronic transplant glomerulopathy (1.6%) showing double contours of the glomerular basement membrane (GBM) on light microscopy. To assess the risk factors, this group was compared with 739 patients with stable function using multivariate Cox regression analysis. Paraffin sections of 11/18 biopsies were stained with polyclonal C4d antibodies. Sera of 13/18 patients could be tested for antidonor human leukocyte antigen (HLA) antibodies by enzyme-linked immunosorbent assay (ELISA). Patients with chronic allograft nephropathy without chronic transplant glomerulopathy or predominant cyclosporine nephrotoxicity were used as controls.

RESULTS

Chronic transplant glomerulopathy was diagnosed at a median of 8.3 (range 2.6-12.5) years posttransplantation. Panel reactive antibodies at time of transplantation, RR 1.23 (1.05-1.45) per 10% increase, and late acute rejection episodes, RR 7.6 (1.8-31.7), were independently associated with chronic transplant glomerulopathy. We found glomerular C4d deposits in 10/11 biopsies showing chronic transplant glomerulopathy and in only 2/13 controls. Peritubular capillary C4d deposits and donor-specific anti-HLA antibodies were demonstrated in 4 and 3 of the 10 patients with glomerular C4d deposits, respectively.

CONCLUSION

Presensitization and late acute rejection episodes were the risk factors identified. Glomerular C4d deposits suggest that chronic transplant glomerulopathy emerges from in situ humoral rejection. Chronic transplant glomerulopathy should be considered as a manifestation of immune-mediated injury.

Glomerular changes in BK virus nephropathy

This study seeks to define the glomerular changes that are associated with human BK virus nephropathy (BKVN). It is based on histopathologic review of 124 biopsies showing light-microscopic changes of viral nephropathy. The diagnosis of BKVN was confirmed by immunohistochemistry or by in situ hybridization. Histological lesions were scored by the Banff 97 criteria for renal allograft pathology and were correlated with clinical parameters. Viral cytopathic effect in the parietal Bowman's capsular epithelium was seen in 21/124 (17%) biopsies. Immunohistochemistry showed infection of Bowman's capsular epithelium in an additional 15/124 (12%) biopsies. Crescents were found in 15/124 (12%) samples. Glomerulitis exceeding grade Banff g1 was only occasionally shown (4/124=3% biopsies). Other pathologic lesions documented include mild increase in mesangial matrix in 23% biopsies, aneurysmal dilatation of glomerular capillaries in 28%, ischemic glomerulopathy in 62%, and chronic transplant glomerulopathy graded as mild (cg1) in 62% of biopsies and as moderate (cg2) in 2/124 (1.9%) biopsies. These findings show that infection of the glomerular epithelium cells can occur in a subset of patients with BKVN, most often in biopsies with high viral load in the tubular epithelium. Isolated crescents can occur in BKVN biopsies, but rapidly progressive glomerulonephritis is not observed. Two biopsies showed electron-dense deposits on ultrastructural examination, but a cause and effect relationship to BK virus infection could not be established.

C4d staining of perioperative renal transplant biopsies

BACKGROUND

Deposition of C4d in peritubular capillaries (PTCs) has been shown to be a sensitive marker for antibody-mediated (humoral) rejection in renal transplant biopsies. Some studies also suggest that C4d in PTCs is specific for humoral rejection or, at least, for the presence of donor-specific antibodies. However, in other studies, PTC C4d deposits were noted in more than 40% of renal transplant biopsies performed for graft dysfunction and capillary C4d deposition in heart transplants may result from ischemic injury.

METHODS

To test the specificity of C4d staining as a marker for acute humoral rejection ACR in renal allografts, indirect immunofluorescence using a monoclonal anti-C4d antibody and a fluorescein-isothiocyanate-conjugated secondary antibody was performed on cryostat sections of 90 renal transplant biopsies, including 35 pairs of preimplantation and 1-hr postreperfusion biopsies of the same graft, postreperfusion biopsies of 12 additional grafts, and 8 positive controls (biopsies with known C4d-positive AHR). Eighteen grafts were cadaveric, 17 grafts were liviing-related, and 12 grafts were living-unrelated (excluding controls). Included in these grafts were 13 grafts that developed AHR 3 to 34 days posttransplantation.

RESULTS

Only 2 of 82 perioperative biopsies showed C4d staining in PTCs. Both perioperative biopsies were postreperfusion biopsies of grafts diagnosed with AHR 5 and 34 days posttransplantation, respectively, and, in each case, the recipient had been treated with plasmapheresis before transplantation because of a positive crossmatch (cytotoxic and flow cytometric) and continued to have a weakly positive flow crossmatch at the time of transplantation. In one biopsy, C4d staining was focal, and in the other biopsy, it was diffuse; in both biopsies, C4d staining was relatively mild (1+ on a 0-4+ scale). No C4d staining was noted on preimplantation biopsies of each graft. All biopsies that contained glomeruli showed linear capillary loop or blotchy mesangial staining, or both, which was similar in prereperfusion and postreperfusion biopsies. All positive controls showed diffuse C4d staining in PTCs.

CONCLUSIONS

C4d staining in PTCs may be seen as early as 1 hr posttransplantation in some recipients with low levels of antidonor antibodies. However, this was not observed as a feature of ischemic or ischemia-reperfusion injury in perioperative renal transplant biopsies, including those of cadaveric grafts with cold ischemia times of as long as 41 hr.