Mfn2 inhibits chronic rejection of the rat abdominal aorta by regulating TGF-β1 levels

OBJECTIVES

The various forms of chronic rejection share a common histological appearance termed allograft arteriosclerosis. In the early stages thereof, apoptosis of vascular smooth muscle cells (VSMC) is obviously reduced, associated with vascular intimal thickening. High-level expression of the HSG/Mfn2 gene promotes apoptosis of rat VSMC. However, the role and mechanism of Mfn2 in inhibition of chronic allograft rejection have not been described.

METHODS

In the present study, we transfected transplanted abdominal aortas of donor Lewis rats with an Mfn2-encoding or control lentivirus. And then We transplanted the donor aortas to the corresponding aortal positions in recipient rats. Transplanted aortas were collected on days 30, 60, and 90 and Masson stained to measure intimal thicknesses. Immunohistochemistry would be used to confirm TGF-β1, Mfn2 and TGF-β-R2 expression in different groups.

RESULTS

Our results confirm that high-level expression of Mfn2 lowers the expression of TGF-β1, reduces the intimal thickness of transplanted rat abdominal aorta, and retards the process of chronic rejection.

CONCLUSION

Mfn2 influences TGF-β/smad pathway and may function as potential chronic rejection inhibitor.

Gut microbiota and its implications in small bowel transplantation

The gut microbiota is mainly composed of a diverse population of commensal bacterial species and plays a pivotal role in the maintenance of intestinal homeostasis, immune modulation and metabolism. The influence of the gut microbiota on solid organ transplantation has recently been recognized. In fact, several studies indicated that acute and chronic allograft rejection in small bowel transplantation (SBT) is closely associated with the alterations in microbial patterns in the gut. In this review, we focused on the recent findings regarding alterations in the microbiota following SBTand the potential roles of these alterations in the development of acute and chronic allograft rejection. We also reviewed important advances with respect to the interplays between the microbiota and host immune systems in SBT. Furthermore, we explored the potential of the gut microbiota as a microbial marker and/or therapeutic target for the predication and intervention of allograft rejection and chronic dysfunction. Given that current research on the gut microbiota has become increasingly sophisticated and comprehensive, large cohort studies employing metagenomic analysis and multivariate linkage should be designed for the characterization of host-microbe interaction and causality between microbiota alterations and clinical outcomes in SBT. The findings are expected to provide valuable insights into the role of gut microbiota in the development of allograft rejection and other transplant-related complications and introduce novel therapeutic targets and treatment approaches in clinical practice.

Impact of immunosuppressive agents on the expression of indoleamine 2,3-dioxygenase, heme oxygenase-1 and interleukin-7 in mesangial cells

Chronic allograft nephropathy (CAN) is a major cause of graft loss following kidney transplantation and may result from the interactions of various immune and non-immune factors. The aim of the present study was to establish an in vitro model of glomerular mesangial cell injury in order to examine the gene expression levels of indoleamine 2,3-dioxygenase (IDO), heme oxygenase-1 (HO-1) and interleukin-7 (IL-7) in mesangial cells during the healing process as well as to investigate the effects of various immunosuppressants on the expression of these genes. The HBZY-1 glomerular mesangial cell line was pre-treated in vitro with cytochalasin B for 2 h to induce reversible damage. Following the pre-treatment, the HBZY-1 cells were divided into five groups: Blank control group, cyclosporine A (CsA) group, tacrolimus (Tac) group, mycophenolate mofetil (MMF) group and rapamycin (RAPA) group. After treating the mesangial cells with each immunosuppressive drug for 6, 12 or 24 h, the mRNA and protein expression levels of IDO, HO-1 and IL-7 were examined using reverse transcription quantitative polymerase chain reaction (RT-qPCR), western blot and immunohistochemical analyses. The results showed that expression levels of HO-1 were significantly upregulated in response to treatment with CsA, FK506, RAPA and MMF, whereas the expression levels of IL-7 were markedly downregulated by treatment with the above immunosuppressants. CsA, FK506 and MMF significantly enhanced the expression levels of IDO, whereas RAPA exhibited no apparent effect on IDO. The present study may contribute to the understanding of the pathogenesis of CAN and provide novel strategies for the prevention and treatment of CAN.

Monocytic Tissue Transglutaminase in a Rat Model for Reversible Acute Rejection and Chronic Renal Allograft Injury

Acute rejection is a major risk factor for chronic allograft injury (CAI). Blood leukocytes interacting with allograft endothelial cells during acute rejection were suggested to contribute to the still enigmatic pathogenesis of CAI. We hypothesize that tissue transglutaminase (Tgm2), a multifunctional protein and established marker of M2 macrophages, is involved in acute and chronic graft rejection. We focus on leukocytes accumulating in blood vessels of rat renal allografts (Fischer-344 to Lewis), an established model for reversible acute rejection and CAI. Monocytes in graft blood vessels overexpress Tgm2 when acute rejection peaks on day 9 after transplantation. Concomitantly, caspase-3 is activated, suggesting that Tgm2 expression is linked to apoptosis. After resolution of acute rejection on day 42, leukocytic Tgm2 levels are lower and activated caspase-3 does not differ among isografts and allografts. Cystamine was applied for 4 weeks after transplantation to inhibit extracellular transglutaminase activity, which did, however, not reduce CAI in the long run. In conclusion, this is the first report on Tgm2 expression by monocytes in vivo. Tgm2 may be involved in leukocytic apoptosis and thus in reversion of acute rejection. However, our data do not support a role of extracellular transglutaminase activity as a factor triggering CAI during self-limiting acute rejection.

Expression of nestin after renal transplantation in the rat

Chronic allograft injury (CAI) limits the long-term success of renal transplantation. Nestin is a marker of progenitor cells, which probably contribute to its pathogenesis. We hypothesize that nestin is induced by ischemia/reperfusion injury and acute rejection, main risk factors for CAI. Syngeneic renal transplantation was performed in Lewis rats and allogeneic transplantation in the Fischer 344 to Lewis strain combination, which results in reversible acute rejection and in CAI in the long-run. The Dark Agouti to Lewis rat strain combination was used to study fatal acute rejection. In untreated kidneys, nestin immunoreactivity was detected in glomeruli and in very few interstitial or microvascular cells. Syngeneic transplantation induced nestin expression within 4 days, which decreased until day 9 and returned to control levels on day 42. Nestin expression was strong during acute rejection and still detected during the pathogenesis of CAI on day 42. Nestin-positive cells were identified as endothelial cells and interstitial fibroblast-like cells co-expressing alpha-smooth muscle actin. A sub-population of them expressed proliferating cell nuclear antigen. In conclusion, nestin is induced in renal grafts by ischemia/reperfusion injury and acute rejection. It is expressed by proliferating myofibroblasts and endothelial cells and probably contributes to the pathogenesis of CAI.

Regulatory T cells as modulators of chronic allograft dysfunction

Chronic allograft dysfunction (CAD) in solid organ transplantation is a principal cause of patient morbidity and late allograft loss. The pathogenesis of CAD is largely secondary to chronic damage by the adaptive immune system and long-term immunosuppression. Manipulating these factors may be possible with the use of regulatory T cells (Treg), which have the ability to suppress specific immune responses and therefore potentially remove the need for immunosuppressive drugs. Studies of CAD in experimental models have demonstrated the capacity for both mouse and human Treg cellular therapy to prevent the development of some manifestations of CAD. Furthermore, a role for Treg has been demonstrated in clinically tolerant transplant patients. Certain immunosuppressive therapies are also proving to be 'Treg friendly' and may be helpful in promoting Treg while maintaining other immunosuppressive activity. With this in mind, monitoring for biomarkers of operational tolerance with tailored immunosuppressive therapy or controlled weaning in conjunction with Treg cellular therapy may be a useful strategy to pursue.

T-cell alloimmunity and chronic allograft dysfunction

Solid organ transplantation is the standard treatment to improve both the quality of life and survival in patients with various end-stage organ diseases. The primary barrier against successful transplantation is recipient alloimmunity and the need to be maintained on immunosuppressive therapies with associated side effects. Despite such treatments in renal transplantation, after death with a functioning graft, chronic allograft dysfunction (CAD) is the most common cause of late allograft loss. Recipient recognition of donor histocompatibility antigens, via direct, indirect, and semidirect pathways, is critically dependent on the antigen-presenting cell (APC) and elicits effector responses dominated by recipient T cells. In allograft rejection, the engagement of recipient and donor cells results in recruitment of T-helper (Th) cells of the Th1 and Th17 lineage to the graft. In cases in which the alloresponse is dominated by regulatory T cells (Tregs), rejection can be prevented and the allograft tolerated with minimum or no immunosuppression. Here, we review the pathways of allorecognition that underlie CAD and the T-cell effector phenotypes elicited as part of the alloresponse. Future therapies including depletion of donor-reactive lymphocytes, costimulation blockade, negative vaccination using dendritic cell subtypes, and Treg therapy are inferred from an understanding of these mechanisms of allograft rejection.

Reduced expression of arrestin beta 2 by graft monocytes during acute rejection of rat kidneys

During acute rejection, numerous pro-inflammatory and cytotoxic monocytes accumulate in the vasculature of experimental renal allografts. Arrestins (ARRBs) are cellular regulators of inflammation, but nothing is known about their expression during rejection. Intravascular mononuclear graft leukocytes were isolated 4 days after kidney transplantation. ARRB1 and ARRB2 mRNA expression was reduced in blood leukocytes from allografts undergoing acute rejection, whereas on the protein level only ARRB2 was changed. Flow cytometry and confocal microscopy revealed ARRB1 and ARRB2 expression by monocytes and T cells, with a selective decrease in ARRB2 expression in monocytes during acute rejection. I-κB directly interacted with ARRB2 and the levels of both proteins strongly correlated. Concomitantly, the mRNA expression of NF-κB targeted genes increased. Our results suggest that activation of blood monocytes in renal isografts is dampened by high ARRB2 levels. During acute rejection, ARRB2 levels are reduced and classical monocyte activation is enabled via NF-κB activation.

Macrophages and kidney transplantation

Macrophages are present within the transplanted kidney in varying numbers throughout its lifespan. Because of their prominence during acute rejection episodes, macrophages traditionally have been viewed as contributors to T-cell-directed graft injury. With growing appreciation of macrophage biology, it has become evident that different types of macrophages exist within the kidney, subserving a range of functions that include promotion or attenuation of inflammation, participation in innate and adaptive immune responses, and mediation of tissue injury and fibrosis, as well as tissue repair. A deeper understanding of how macrophages accumulate within the kidney and of what factors control their differentiation and function may identify novel therapeutic targets in transplantation.

Graft inflammation and histologic indicators of kidney chronic allograft failure: low-expressing interleukin-10 genotypes cannot be ignored

BACKGROUND

Infiltration of inflammatory cells into the renal allograft interstitium is the biologic hallmark of alloimmune responses that leads to tubulointerstitial injury and subsequent interstitial fibrosis and chronic allograft failure. The proliferation, stimulation, and infiltration of these inflammatory cells are governed by various proinflammatory and regulatory cytokines. We assessed whether the differences in the genes encoding cytokines (producing low, moderate, or high expression profiles) may affect the infiltration of inflammatory cells into the renal allograft and the histologic changes characteristics of chronic allograft failure.

METHODS

A total of 218 kidney transplant recipients were genotyped for 15 single-nucleotide polymorphisms located in the gene promoter or exonic regions of 10 different cytokines or their receptors. Six- to 12-month posttransplant surveillance biopsies were scored using 11 individual histologic parameters and the combined grade of interstitial fibrosis and tubular atrophy (IF/TA). B-cell, T-cell, and macrophage infiltrates were quantified by immunostaining.

RESULTS

The low-expressing interleukin (IL)-10 gene promoter genotypes were found significantly associated with high IF/TA grade (IL-10 -819 TT; P=0.035; odds ratio=3.27; 95% confidence interval 1.1-9.8). At individual histologic indices, recipients carrying low-expressing IL-10 genotypes showed 2.5-fold higher scores for interstitial fibrosis, inflammation, and tubular atrophy. High infiltration of T cells and macrophages but not B cells into the renal allograft interstitium was found strongly associated with the carriage of low-expressing IL-10 genotypes.

CONCLUSIONS

The results suggest that renal transplant recipients genetically predisposed to low expression of the regulatory cytokine IL-10 are more susceptible to high grades of IF/TA scores, graft inflammation, and high influx of inflammatory cells into the graft interstitium.

Leukocyte accumulation in graft blood vessels during self-limiting acute rejection of rat kidneys

During self-limiting acute rejection preceding chronic vasculopathy, large amounts of leukocytes, predominantly monocytes, interact with the endothelium of renal allografts. We aim to characterize them and to identify targets for functional and interventional studies. Leukocytes were harvested by vascular perfusion from Fischer 344 to Lewis renal allografts or Lewis isografts, followed by flow cytometry, quantitative RT-PCR and genome-wide transcriptional profiling. Leukocyte accumulation peaked in allografts on day 9. The percentage of monocytes expressing MHC class II and CD161 was increased whereas CD4, CD11a, CD43, and CD71 expression remained unchanged. IFN-γ, IL-1β, IL-2, IL-10, TNF-α, and iNOS mRNA increased in allograft leukocytes but IL-4, IL-6, IL-12, TGF-β, and tissue factor did not. During acute rejection, 1783 genes were differentially expressed. In conclusion, graft blood leukocytes display a unique state of partial activation during self-limiting rejection. Numerous differentially expressed genes deserve further investigation as potential factors in deciding the fate of the allograft.

Potential differences in kidney allograft outcomes between ethnicities when converting to sirolimus base immunosuppression

OBJECTIVE

The aim of this study was to determine whether ethnicity impacts graft outcomes in kidney transplant patients converted to sirolimus (SRL) and maintained on either calcineurin inhibitors (CI) or mycophenolate mofetil (MMF) with steroids.

METHODS

This study analyzed kidney transplants converted to SRL and transplanted between July 1991 and April 2007. Patients were divided into 4 groups: group 1: African-Americans converted to SRL + CI; group 2: non-African-Americans converted to SRL + CI; group 3: African-Americans converted to SRL + MMF; group 4: non-African-Americans converted to SRL + MMF.

RESULTS

A total of 242 patients was included. Demographics, baseline immunosuppression, and reason for SRL conversion were similar among groups. Patients converted to SRL + CI regimens had significantly higher rates of acute rejection before SRL conversion, but equal rates after conversion. Development of proteinuria was similar across groups. African-American patients converted to SRL + MMF tended to have poorer outcomes compared with African-American patients converted to SRL + CI. Non-African-American patients converted to SRL + MMF tended to have better graft outcomes compared with non-African-American patients converted to SRL + CI.

CONCLUSIONS

African-Americans converted to SRL may benefit from continued CI, whereas non-African-Americans converted to SRL seem to have better outcomes with MMF. Further prospective studies are warranted to confirm these findings.

Conversion from cyclosporin A to sirolimus retards the progression of chronic allograft nephropathy in the long term in a rat kidney transplantation model

In a rat renal allograft model, the long-term effect of conversion from cyclosporin A (CsA) to sirolimus on recipient kidneys and growth factor expression were compared with continuous use or withdrawal of CsA. Kidneys from Fisher 344 rats were orthotopically transplanted into Lewis rats. Four Fisher 344 to Lewis allograft groups were treated post-transplant as follows: (i) CsA (transplant to week 8) then sirolimus (weeks 8 - 24); (ii) CsA (transplant to week 24); (iii) CsA (transplant to week 8) then vehicle (weeks 8 - 24); (iv) control vehicle (transplant to week 24). A fifth group underwent syngeneic isograft (Lewis to Lewis) with no drug treatment. Proteinuria was measured every 4 weeks and grafts harvested at 24 weeks for morphological and immunohistochemical analysis. Conversion from CsA to sirolimus resulted in a significant decrease in proteinuria at 24 weeks, a lower Banff sum score and lower expression of transforming growth factor mRNA compared with continuous use or withdrawal of CsA. In conclusion, conversion from CsA to sirolimus retarded progression of chronic allograft nephropathy in the rat model.

Balance of transforming growth factor-beta1 and platelet-derived growth factor-BB is associated with kidney allograft rejection

BACKGROUND

About 50% of kidney-transplant patients undergo organ rejection within 10 years. Chronic allograft nephropathy (CAN) represents the dominant cause of kidney transplant failure and accounts for 50-80% of graft loss in long-term surviving patients. CAN pathogenesis is multifactorial and not-completely elucidated; several reports indicate TGF-beta1 and platelet-derived growth factor (PDGF)-BB expression in CAN suggesting a possible role of these factors in the allograft arteriosclerosis and graft failure.

METHODS

We investigated the plasma expression concentrations of human growth factors with enzyme-linked immunosorbent assays and appropriate statistical analysis.

RESULTS

We present evidences showing statistically significant association of CAN with a specific balance between TGF Beat1 and PDGF-BB plasma concentrations, in 129 kidney-transplant patients and 15 healthy controls. Odds ratios were computed to correlate expression-levels with CAN occurrence.

CONCLUSION

We believe these data may suggest a novel non-invasive method to identify early molecular markers of graft deterioration.

Sex differences in response to cyclosporine immunosuppression in experimental kidney transplantation

1. Female donors and recipients have increased risk of acute rejection and subsequent chronic allograft nephropathy (CAN), especially when cyclosporine A (CsA) is used. Decreased renal nitric oxide (NO) production is associated with chronic kidney disease. In the present study, we investigated the impact of gender, CsA dose and renal NO synthase (NOS) on CAN. 2. Kidneys from male and female F344 rats were transplanted into same-sex Lewis allograft or F344 isograft recipients and recipient rats were treated with 1.5 or 3 mg/kg per day CsA for 10 days. Grafts were removed at 22 weeks post-transplantation. Normal two-kidney F344 rats were investigated as age-matched controls. 3. Low-dose CsA was associated with accelerated CAN in female rats compared with male rats; however, with high-dose CsA, allograft females had similar pathology/function to allograft males. Isograft females (similar to isograft males) had no graft failure and only slightly, albeit significantly, greater injury than age-matched controls. Isograft females had higher renal cortical neuronal (n) NOS but lower medullary endothelial (e) NOS than isograft males. There was no difference in renal eNOS and nNOS between allograft groups. 4. In conclusion, 1.5 mg/kg per day CsA is not sufficient to prevent early graft loss in females. When the dose of CsA is doubled, allograft females and males have similar post-transplant survival. Renal NOS expression was unremarkable in any transplant group.

FTY720 reduces extracellular matrix expansion associated with ischemia-reperfusion induced injury

BACKGROUND

Ischemia-reperfusion (IR) is one of the strongest nonimmune factors associated with the development of chronic allograft nephropathy (CAN). This effect is often exacerbated by immunosuppressive medications, most notably cyclosporine. Although traditionally the macrophage was thought to stimulate fibroblast activity in CAN, recent evidence supports a role for lymphocytes. FTY720 is a new immunosuppressant that promotes lymphocyte sequestration into lymph nodes and Peyer's patches. This study investigated the effect of FTY720 on renal fibrosis in the rat following an IR insult (IRI).

METHODS

A rat model of IRI was used in which male Sprague-Dawley rats (under isoflurane anaesthesia) underwent bilateral flank incision with removal of the right kidney and clamping of the left renal hilum for 45 minutes. Five groups of animals were studied (n=4): nephrectomy only, IRI only, IRI+FTY720 (1 mg/kg/d), IRI+cyclosporine (15 mg/kg/d), and IRI+FTY 720 (1 mg/kg/d) and cyclosporine (15 mg/kg/d). Animals were humanely killed at 30 days.

RESULTS

Serum creatinine (SCr) level was significantly reduced in the FTY720-treated animals. IRI alone produced a significant increase in SCr level compared with neprectomized animals (138 micromol/L vs 55 micromol/L; P<.05). This effect was potentiated by treatment with cyclosporine (173 micromol/L vs 55 micromol/L; P<.05). Treatment with FTY720 significantly reduced SCr level in rats following IRI alone (81 micromol/L vs 138 micromol/L; P<.01) and in rats following IRI + cyclosporine (98 micromol/L vs 173 micromol/L; P<.014). Parallel changes were seen in the levels of proteinuria. Fibrosis was assessed using Masson's trichrome (MT) staining. IRI alone produced a significant increase in MT staining compared with nephrectomized animals (0.92 vs 0.03; P<.05). This effect was potentiated by treatment with cyclosporine (1.12 vs 0.92; P=.022). Treatment with FTY720 reduced the level of MT staining in rats following IRI alone (0.34 vs 0.92; P<.05) and in rats following IRI+cyclosporine (70.34 vs 1.12; P<.05). Levels of TGF-beta1 were considerably reduced in FTY720-treated animals (compared with cyclosporine+IRI and IRI only), either alone (196+/-31 pg/mL vs 1105+/-59 pg/mL and 611+/-38; P<.05) or in conjunction with cyclosporine (423+/-26 pg/mL vs 1105+/-59 pg/mL and 611+/-38; P<.05).

CONCLUSION

Our study shows that treatment with FTY720 can reduce renal fibrosis as a result of IRI, both alone and in conjunction with cyclosporine. This provides promising evidence for using FTY720 in a calcineurin-free or reduced-dose immunosuppression protocol in an effort to reduce the incidence of CAN.

The origin of neointimal smooth muscle cells in transplant arteriosclerosis from recipient bone-marrow cells in rat aortic allograft

In order to investigate the origin of neointimal smooth muscle cells in transplant arteriosclerosis in rat aortic allograft, sex-mismatched bone marrow transplantation was performed from male Wistar rats to female Wistar rats. Four weeks after transplantation, the aortic transplant model was established by means of micro-surgery in rats. The recipients were divided into 4 groups: female Wistar-female Wistar aortic isografts, female SD female Wistar aortic allografts, male SD-male Wistar aortic allografts, female SD-chimera Wistar aortic allografts. Eight weeks after transplantation, aortic grafts were removed at autopsy and processed for histological evaluation and immunohistochemistry. The results indicated that excessive accumulation of alpha-SMA-positive smooth muscle cells resulted in significant neointima formation and vascular lumen stricture in rat aortic allografts. Neointima assay revealed that the neointimal area and NIA/MA ratio of transplanted artery were significantly increased in all of aortic allograft groups as compared with those in aortic isograft group (P<0.01). Neointimal smooth muscle cells were harvested from cryostat sections of aortic allograft by microdissection method. The Sry gene-specific PCR was performed, and the result showed that a distinct DNA band of 225 bp emerged in the male-male aortic allograft group and chimera aortic allograft group respectively, but not in the female-female aortic allograft group. It was suggested that recipient bone-marrow cells, as the origin of neointimal smooth muscle cells, contributed to the pathological neointimal hyperplasia of aortic allograft and transplant arteriosclerosis.

Evaluating the accuracy of functional biomarkers for detecting histological changes in chronic allograft nephropathy

The most common cause of late kidney transplant failure is chronic allograft nephropathy (CAN). Much research has focused on identifying biomarkers (or correlates) that would predict subsequent CAN and allow timely intervention. Functional biomarkers such as serum creatinine and estimated glomerular filtration rate (eGFR) have been widely adopted, even though they have not been rigorously evaluated as surrogate markers. This study evaluated serum creatinine and eGFR for predicting the early histopathological changes seen in transplant protocol biopsies (TPB). We prospectively followed 289 kidney transplant patients in the Southern Alberta Transplant Program who had TPB at 6-12 months post-transplant. Tissue samples (n = 280) were independently examined by renal pathologists. The ability of serum creatinine or eGFR to predict the threshold level for abnormal histopathology was evaluated by calculating the area under the receiver operator characteristic curve. Serum creatinine and eGFR had poor predictive value (most confidence intervals included 0.5, indicating no predictive ability) for ten individual histological measurements (Banff 97 scores), and the Chronic Allograft Damage Index. We conclude that serum creatinine and eGFR have a limited clinical role in predicting the early histopathological changes that precede CAN and should not be used for this purpose.

Sirolimus is not always responsible for new-onset proteinuria after conversion for chronic allograft nephropathy

An eight-yr-old combined liver and kidney transplant recipient for hyperoxaluria type I developed significant proteinuria and hypertension after conversion of a Tacrolimus, MMF, and corticosteroids-based immunosuppression to Sirolimus, low-dose Tacrolimus, and corticosteroids six and a half yr after the transplant for chronic allograft nephropathy. There was only one class I HLA match and the recipient had multiple blood exposures prior to transplantation. The patient was treated with combined hemodialysis and peritoneal dialysis while awaiting transplantation to reduce the oxalate load. A renal biopsy revealed a de novo transplant glomerulopathy that was associated with specific HLA antibodies unrelated to the donor (HLA DR 17 and 18). After reintroduction of MMF, these antibodies became undetectable and the proteinuria completely resolved. We hypothesize that HLA antibodies may cause transplant glomerulopathy even if they are not donor-specific. Their production appears more susceptible to MMF therapy. A thorough work-up of new-onset proteinuria after conversion to Sirolimus should be performed, including an immunological work-up and a renal biopsy.

Effects of Everolimus on Cellular and Humoral Immune Processes Leading to Chronic Allograft Nephropathy in a Rat Model with Sensitized Recipients

BACKGROUND

Chronic allograft nephropathy (CAN) remains the most common cause of late graft loss especially in sensitized patients. The aim of this study is to evaluate the therapeutic effect of everolimus on cellular and humoral mechanisms of chronic allograft damage in a rat model with sensitized recipients.

METHODS

F344 kidneys were transplanted to LEW.RNU rats. The athymic recipients were reconstituted with 3.5 x 10(7) or 5 x 10(7) presensitized CD4+T-lymphocytes. In the treatment group, everolimus was introduced five weeks posttransplantation. Rats were monitored for peripheral blood lymphocytes, renal function, histological changes in the graft, and the development of donor-specific alloantibodies.

RESULTS

Rats developed cell dose-dependent renal failure. Increased urinary albumin excretion and glomerulopathy were frequently accompanied by the development of donor-specific major histocompatibility complex (MHC) alloantibodies. In the everolimus group, five of six animals survived for 20 weeks with stable serum creatinine and displayed neither acute cellular rejection nor CAN. Prolonged survival was accompanied with significantly reduced tubulointerstitial cell infiltrate in the graft. Increased urinary albumin excretion was present in all, acute tubular necrosis in five of six, and glomerular sclerosis in two grafts. MHC alloantibodies were found in four of six animals.

CONCLUSION

The used rat model offers the opportunity to study the influence of everolimus on the interaction of humoral and cellular mechanisms involved in chronic renal damage. Everolimus leads to a prolongation of allograft survival, reduced cell infiltrate in the graft, and prevents tubular atrophy and interstitial fibrosis. The development of alloantibodies and albuminuria was not prevented. These data suggest that although cellular rejection is clearly suppressed, humoral mechanisms of CAN cannot be completely controlled by everolimus treatment in the sensitized rat model.

Conversion from calcineurin inhibitors to sirolimus for chronic renal allograft dysfunction: a systematic review of the evidence

BACKGROUND

Conversion from a calcineurin inhibitor to sirolimus has been used as a strategy to improve deteriorating renal allograft function but the efficacy and safety of this intervention is unknown.

METHODS

We performed a systematic review of studies that involved conversion from a calcineurin inhibitor to sirolimus in kidney transplantation. The search yielded five randomized trials (n=1,040 patients) and 25 nonrandomized studies (n=977 patients).

RESULTS

In the randomized trials, conversion to sirolimus improved short-term creatinine clearance (weighted mean difference 6.4 mL/min; 95% CI 1.9 to 11.0) compared to controls. In the nonrandomized studies, renal function improved or stabilized in 66% (95% CI 61% to 72%), creatinine clearance improved (weighted mean change 5.7 mL/min; 95% CI 1.4 to 10.1), cholesterol increased (weighted mean change 20.8 mg/dL; 95% CI 11.2 to 30.4) and triglycerides increased (weighted mean change 40.1 mg/dL; 95% CI 18.6 to 61.7). Sirolimus was discontinued by 28% of patients (95% CI 0 to 59%) in the randomized trials and 17% (95% CI 12 to 22%) in the nonrandomized trials.

CONCLUSION

Conversion to sirolimus is associated with an improvement in short-term renal function. However, given the discontinuation rate and potential side effects, adequately powered randomized trials with longer follow-up of hard outcomes are needed to determine whether this strategy leads to a lasting benefit in the clinical care of transplant recipients.

Face Transplantation: A Review of the Technical, Immunological, Psychological and Clinical Issues with Recommendations for Good Practice

Three years ago, the Working Party on Facial Transplantation concluded that until there was more information available about risks any potential patient would be exposed to, it would be unwise to proceed with transplantation of the human face. Over the last three years, there has been a deepening understanding of the potential psychological problems of facial transplantation as well as a very considerable debate on the ethical aspects of the procedure. Further data on experimental work in animal models of facial transplantation as well as medium-term follow-up data from 24 hand and forearm transplants in 18 patients has now become available. Furthermore, a partial facial transplantation has been performed in France and a second one in China. In this second edition of the report, the technical, immunological, psychological, and ethical issues are discussed again in the light of this developing knowledge. In particular, there has been a major expansion of the sections on the psychological and societal issues, as well as the ethical and legal problems of facial transplantation. The working party still has considerable reservations about facial transplantation. Although it accepts that on balance the risks cannot be precisely quantified, they remain substantial. Therefore, if patients are allowed to make an informed choice to proceed, they must be very carefully selected and protected in the process, along with the families of both the donors and the recipients. To achieve this, the working party insists that 15 minimum requirements, described at the end of this report, must be fulfilled before it would be appropriate for a research ethics committee/institutional review board to approve of a proposal to undertake facial transplantation.

Adenovirus-Mediated Antisense-ERK2 Gene Therapy Attenuates Chronic Allograft Nephropathy

BACKGROUND

The aim of this study was to investigate the effects of adenovirus-mediated antisense ERK2 (Adanti-ERK2) gene therapy on chronic allograft nephropathy.

METHODS

We employed a rat kidney transplantation mode (F344-->Lewis) and studied four groups: (1) controls (n = 6); (2) vector controls (n = 6); (3) an Adanti-ERK2 group (n = 10); and (4) an isograft group (n = 4). The animals were monitored for proteinuria, graft histology, infiltrating cells, and immune-related gene (interleukin-2 [IL-2] and intracellular adhesion molecule-1 [ICAM-1]) expression for 20 weeks after transplantation.

RESULTS

The control group had increasing proteinuria during the 20-week follow-up. All rats showed advanced chronic renal failure associated with strong immune cell infiltration and immune gene expression. Chronic graft injury was accelerated in the vector-control group, but no significant difference was observed compared with the control group. In contrast, the Adanti-ERK2 group showed less inflammation and improved graft histology/function compared with controls. Moreover, ERK2 protein expression in the Adanti-ERK2 group was lower than in the control group (P < .05) and vector-control group (P < .05). Furthermore, serial estimates of genes (IL-2, ICAM-1) related to chronic rejection showed significant downregulation in the Adanti-ERK2 group (P < .01).

CONCLUSIONS

Adenovirus-mediated antisense ERK2 gene therapy attenuated chronic allograft nephropathy. The protective effects of antisense ERK2 gene therapy may have derived from a blocked ERK signal transduction pathway, which reduced ERK expression as well as those of immune-related genes.

Pivotal role of complement-fixing HLA alloantibodies in presensitized kidney allograft recipients

Recipient presensitization represents a major risk factor for kidney allograft loss. Complement fixation may be a critical attribute of deleterious alloantibodies. We investigated clinical impact of complement-fixing HLA presensitization employing [C4d]FlowPRA, a novel assay permitting selective detection of HLA panel reactive antibody (PRA)-triggered C4 complement split product deposition. A cohort of 338 kidney transplants was evaluated for presensitization applying [C4d]FlowPRA together with [IgG]FlowPRA and complement-dependent cytotoxicity (CDC)-PRA. Analysis of HLA class I alloreactivities revealed a high incidence of C4d-positive graft dysfunction in [IgG]FlowPRA(+)/[C4d]FlowPRA(+) and [IgG]FlowPRA(+)/[C4d]FlowPRA(-) recipients (23% and 22% vs. 3% in [IgG]FlowPRA(-) patients). Only patients with complement-fixing HLA class I immunization had inferior graft survival [75% (3 years) vs. 91% and 89%, respectively (p=0.036)]. Despite frequent finding of capillary C4d deposition (28%), complement-fixing HLA class II immunization was not associated with inferior survival rates. This may have been due to reduction of clinical effects by intense immunosuppression in presensitized patients. Evaluating CDC, 29% of CDC-PRA(+)/[C4d]FlowPRA(+) recipients had C4d-positive graft dysfunction. For these patients 3-year graft survival was worst, followed by CDC-PRA(+)/[C4d]FlowPRA(-) and CDC-PRA(-) patients (76% vs. 81% vs. 90%, p=0.014). Results highlight a strong impact of complement-fixing HLA presensitization. Discerning complement-activating abilities of HLA alloantibodies, [C4d]FlowPRA may help identify recipients at particularly high risk for graft rejection and loss.

The role of macrophages in allograft rejection

Macrophage accumulation has long been recognized as a feature of allograft rejection, yet the role of macrophages in rejection remains underappreciated. Macrophages contribute to both the innate and acquired arms of the alloimmune response and thus may be involved in all aspects of acute and chronic allograft rejection. Recent advances in macrophage biology have allowed a better understanding of the mechanisms of macrophage accumulation, their state of activation and the pleuripotent roles they play in allograft rejection. Therapeutic attention to macrophages, in addition to T lymphocytes, may lead to improved outcomes in organ transplantation.

Multiple potential clinical benefits for 1alpha,25-dihydroxyvitamin D3 analogs in kidney transplant recipients

Therapeutic trials of 1alpha,25(OH)(2)D(3) and related synthetic analogs are merited in diverse clinical fields, including treatment or prevention of bone disease, cancer, immune-mediated diseases, cardiovascular diseases, and prostatic hypertrophy. Potential difficulties of carrying out such trials successfully, include experimental data suggesting relatively modest therapeutic effects of 1alpha,25(OH)(2)D(3) analogs as stand-alone intervention and the likely requirement for large study group size and lengthy follow-up periods, if individual prophylactic effects are to be proven. Thus, it may be wise to identify patient groups with multiple potential benefits, accelerated disease risks, and the possibility for exploring synergistic pharmacological effects, in whom to carry out clinical trials of 1alpha,25(OH)(2)D(3) analogs. With this consideration in mind, the suitability of kidney transplant recipients for such studies is discussed. Although, highly effective in reversing end-stage renal disease, kidney transplantation continues to be limited by heightened risk of osteoporosis, persistent hyperparathyroidism, acute and chronic immunological injury, new cancer diagnosis, and cardiovascular events. In addition, kidney transplant recipients generally receive multiple immunosuppressants with a high prevalence of medication-related toxicities. Finally, it is pointed out that clinical trials carried out in organ transplant recipients provide a unique opportunity for longitudinal comparison of target tissue structural and gene expression profiles among treated and control patient groups. It is proposed that addition of a 1alpha,25(OH)(2)D(3) analog to conventional post-kidney transplant medication regimens is likely to be associated with measurable effects to prevent or retard multiple important complications and that this patient group is especially suitable for carrying out clinical trials of these compounds.

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 micromol/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.

Chronic renal allograft rejection: Pathophysiologic considerations

Chronic rejection is currently the most prevalent cause of renal transplant failure. Clinically, chronic rejection presents by chronic transplant dysfunction, characterized by a slow loss of function, often in combination with proteinuria and hypertension. The histopathology is not specific in most cases but transplant glomerulopathy and multilayering of the peritubular capillaries are highly characteristic. Several risk factors have been identified such as young recipient age, black race, presensitization, histoincompatability, and acute rejection episodes, especially vascular rejection episodes and rejections that occur late after transplantation. Chronic rejection develops in grafts that undergo intermittent or persistent damage from cellular and humoral responses resulting from indirect recognition of alloantigens. Progression factors such as advanced donor age, renal dysfunction, hypertension, proteinuria, hyperlipidemia, and smoking accelerate deterioration of renal function. At the tissue level, senescence conditioned by ischemia/reperfusion (I/R) may contribute to the development of chronic allograft nephropathy (CAN). The most effective option to prevent renal failure from chronic rejection is to avoid graft injury from both immune and nonimmune mechanism together with nonnephrotoxic maintenance immunosuppression.

Surgical transplant physical examination: correlation of renal resistance index and biopsy-proven chronic allograft nephropathy

BACKGROUND

Chronic allograft nephropathy (CAN) remains the leading cause of late renal allograft loss that is minimally responsive to therapy once graft dysfunction is clinically evident. A screening test capable of identifying individuals at high risk for CAN would be a valuable adjunct to patient care, but to be cost effective, should be administered during routine evaluations by transplantation clinicians.

STUDY DESIGN

We have compared the resistive index (RI) as measured by Doppler ultrasonography with subsequent biopsy findings on 91 renal allograft recipients who had a subsequent protocol-directed biopsy at least 3 months after renal transplant. All ultrasonography was performed by the transplantation surgical staff without involving the radiology department or a separate appointment time.

RESULTS

Twenty-one patients had RI >/= 80 (average 621 days posttransplantation). Among these individuals, the subsequent incidence of CAN was 38%. Length of time between initial assessment of increased RI and biopsy-proved CAN averaged 233 days. The remaining 70 patients with RI < 80 had an incidence of CAN of 11.4% (p = 0.018). There were minimal complications from these biopsies. Sensitivity and specificity of an elevated RI in predicting CAN were 50% and 83%, respectively. The negative predicted value of an elevated RI in determination of CAN was 89%.

CONCLUSIONS

These results suggest that elevated RI is an early predictor of histologically relevant CAN, possibly a result of burgeoning vasculopathy. The technical expertise required to make this appraisal is well within the capabilities of transplantation surgeons and trainees. Early evidence of CAN may allow for a targeted change in therapy before clinically significant injury. Ultrasonography should become a routine part of a transplantation clinic evaluation.

Adoptive transfer of primed CD4+ T-lymphocytes induces pattern of chronic allograft nephropathy in a nude rat model

BACKGROUND

Chronic allograft nephropathy (CAN) remains the most common cause of late graft loss in renal transplantation. Presensitized patients have a specifically increased risk to lose their graft. To analyze the immunological factors involved, a new experimental rat model was created with nude athymic LEW.RNU rats as recipients of F344 renal allografts.

METHODS

Adoptive transfer of CD4+ T-lymphocytes (2x, 3.5x, or 5 x 10(7) cells) primed against donor skin grafts was performed one week after transplantation. The animals were monitored for renal function, graft infiltrating cells, and the development of donor specific alloantibodies for 20 weeks or until graft loss.

RESULTS

Survival of the animals was dose dependent; rats suffered from renal failure with severe albuminuria and developed various lesions typical for CAN including interstitial fibrosis and tubular atrophy. The cell infiltrate in the graft increased with the amount of CD4+ T-cells transferred and consists predominantly of CD4+ T-cells and macrophages/monocytes. More than half of the grafts showed histological signs of glomerulopathy consistent with CAN. 9/12 rats with CAN had antibodies against the donor major histocompatibility complex (MHC)-I and in all rats donor specific anti-glomerular basement membrane (GBM) antibodies were detected.

CONCLUSION

Adoptive transfer of primed CD4+ T-cells results in a severe infiltrate of CD4+ cells in the graft and production of anti-MHC and GBM antibodies in this nude rat model. Histological changes are consistent with CAN with frequent glomerular changes. In conclusion, the induction of donor specific alloantibodies by primed CD4+ T-lymphocytes may play an important role in the pathogenesis of CAN.

Impact of ELISA-Detected Anti-HLA Antibodies on Pediatric Cardiac Allograft Outcome

In this study, we determine whether the presence of enzyme-linked immunosorbent assay (ELISA) detected anti-human leukocyte antigen (HLA) antibodies correlates with acute and chronic rejection in pediatric heart transplantation (Tx). Forty-five patients, who had serial ELISA pre- and posttransplantation, were studied. Age at Tx was 8.2 +/- 7.2 years. Acute rejection (AR) was defined as International Society for Heart and Lung Transplantation Grade > or =3a. Patients were defined as rejectors (22 cases) if they had recurrent AR or steroid-resistant AR within the first year post-Tx; the other cases (23) were defined as nonrejectors. Overall, 219 samples were analyzed. Twenty-two of the 45 had pre- or post-Tx anti-HLA antibodies: 77% in rejectors (17/22) and only 22% in nonrejectors (5/23), p = 0.0002. Pre-Tx HLA antibodies were present in 12 cases (27%). Presensitization was more frequent in rejectors (11/22, 50%) than in nonrejectors (1/23, 4%, p = 0.0005). Nineteen cases retained (9 cases) or developed (10 cases) anti-HLA antibodies post-Tx: 14 in rejectors (63.6%) and 5 in nonrejectors (21.7%), p = 0.003. Four of eight cases with coronary artery disease (50%) had preformed anti-HLA antibodies compared with 8 of 37 without coronary artery disease (25.6%) (p = 0.09). Preformed, persistent, and de novo ELISA-detected anti-HLA antibodies were correlated with first-year acute rejection profile.

Risk Factors for Allograft Failure in United Kingdom Renal Transplant Recipients Treated with Cyclosporine A

BACKGROUND

After the introduction of cyclosporine A (CsA), 2-year graft survival of transplanted kidneys improved from less than 60% to more than 80%, but long-term graft survival and graft half-life have shown less change. This study investigates the impact of a range of demographic and treatment factors on long-term graft survival in renal recipients treated with CsA from all renal transplant centers in the United Kingdom.

METHODS

Data were obtained from the Long-Term Efficacy and Safety Surveillance study of renal transplant recipients receiving CsA (Neoral; Novartis, Basel, Switzerland). A total of 1,757 de novo patients with a functioning graft at 1 year were evaluated. The endpoints considered were the need for regular dialysis or death. A stepwise stratified Cox model was used to identify the factors associated with outcome.

RESULTS

Seven independent risk factors for allograft failure were identified: older recipient (hazard ratio [HR] 1.8, 95% confidence interval [CI] 1.2-2.6), male recipient (HR 1.8, 95% CI 1.2-2.7), younger donor (HR 1.7, 95% CI 1.2-2.5), above average creatinine (HR 1.9, 95% CI 1.3-2.8), chronic allograft nephropathy (HR 7.0, 95% CI 4.7-10.4), diabetic recipient (HR 2.2, 95% CI 1.2-4.1), and neoplasm after transplant (HR 1.7, 95% CI 1.2-2.6).

CONCLUSION

Seven independent risk factors were found to influence graft survival. Only two of these can be modified by clinical intervention, elevated serum creatinine at 1 year and the occurrence of chronic allograft nephropathy. To influence these two factors, the optimization of immunosuppressive therapy is essential.

Different roles for matrix metalloproteinase-2 and matrix metalloproteinase-9 in the pathogenesis of cardiac allograft rejection

Recent studies have shown an increased expression of several matrix metalloproteinases (MMP) during cardiac, renal and pulmonary allograft rejection. To further define the roles of MMP-2 and MMP-9 in the pathogenesis of cardiac allograft rejection, BALB/c cardiac allografts were transplanted into MMP-2-deficient (-/-) and MMP-9-/- mice. Allografts rejected by wild-type mice revealed a significant increase in MMP-2 and MMP-9 expression. MMP-2-deficiency significantly prolonged allograft survival time. Functioning allografts harvested from MMP-2-/- mice showed lower cellular infiltration and fibrosis than rejected allografts harvested from MMP-2+/+ mice at the same time. In contrast, MMP-9-deficiency significantly decreased allograft survival time. Functioning allografts harvested from MMP-9+/+ mice showed lower cellular infiltration and fibrosis than rejected allografts harvested from MMP-9-/- mice at the same time. MMP-2-/- recipients showed decreased T-cell alloreactivity mediated by a defect in dendritic cell stimulatory and T-cell responsive capacities. In contrast, MMP-9-/- recipients showed increased T-cell alloreactivity mediated by a significant increased in dendritic cell stimulatory and T-cell responsive capacities. These results indicate that MMP2 and MMP-9 play significantly different roles in the process of cardiac allograft rejection.

Antibodies against mesangial cells in a rat model of chronic renal allograft rejection

BACKGROUND

Chronic renal allograft rejection (CR) is the leading cause of late renal transplant failure. The histological lesions of CR may comprise glomerular basement membrane (GBM) duplications and mesangiolysis. Its pathogenesis is not yet completely understood, although lately humoral responses have been suggested to be important. Recently, we identified antibody responses directed against GBM antigens in the Fischer (F344) to Lewis (LEW) renal transplantation model. Immunofluorescent studies in this model also suggested deposition of antibodies on mesangial cells. Therefore, we hypothesized that antibodies were not only directed at GBM antigens but also to mesangial cell antigens.

METHODS

F344 to LEW renal transplantations were performed and sera were collected. Pre- and post-transplantation sera were tested for antibody binding to donor rat mesangial cells (RMCs) cultured from F344 kidneys. Anti-mesangial cell antibodies were compared with anti-GBM antibodies measured in the same sera.

RESULTS

Post-transplant sera of F344 to LEW renal transplantations, but not LEW to F344, bound to F344 RMC in a dose-dependent manner. Whereas antibodies reactive with RMCs were not present before transplantation, all rats with CR developed antibodies. The antibodies were predominantly of the IgG1 isotype. Antibody binding to RMCs correlated with binding to F344 GBM. Pre-incubation with RMCs partially inhibited GBM binding, and RMC binding was inhibited by GBM. Antibody binding to RMCs did not result in complement activation or cell lysis.

CONCLUSION

LEW recipients of F344 grafts produce antibodies reactive with F344 RMCs. The antigens involved are similar to or at least share antigenic epitopes with antigens recognized in the GBM.

Injury and progressive loss of peritubular capillaries in the development of chronic allograft nephropathy

BACKGROUND

Chronic allograft nephropathy (CAN) remains the most important cause of late renal graft loss. However, the mechanism for graft dysfunction and the process of the development of CAN are not well understood. This study examined the role of microvascular injury in the development of CAN.

METHODS

We studied renal biopsies obtained from grafts with CAN (N= 79) and pretransplant control kidneys (N= 20). Microvascular injury was examined morphologically, and was correlated with interstitial fibrosis, glomerular sclerosis, graft function, and the severity of CAN. The humoral and cellular immunity involved in CAN were examined by C4d, CD3, and TIA-1 staining.

RESULTS

In all the cases of CAN, microvascular injury was evident with or without CD3-positive T cells, TIA-1-positive cytotoxic cells, and/or C4d+ complement deposition. Irrespective of chronic rejection (N= 14), C4d+ chronic humoral rejection (N= 6), or other CAN, the development process of CAN was characterized by injury and progressive loss of identifiable peritubular capillaries (PTCs) accompanied with the development of interstitial fibrosis. Injured PTCs were characterized morphologically by the process of angioregression with the presence of apoptotic cells, lamination of the basement membrane, and loss of PTCs. The low number of PTCs correlated significantly with the severity of CAN (r=-0.74, P < 0.001), the development of interstitial fibrosis (r=-0.75, P < 0.001), graft dysfunction (r=-0.69, P < 0.001), and also correlated weakly with proteinuria (r=-0.45, P < 0.05). In the glomeruli, capillary loss significantly correlated with the degree of glomerular sclerosis (r=-0.66, P < 0.001) and proteinuria (r=-0.65, P < 0.001), but did not correlate with the severity of CAN (r=-0.24, P > 0.05) or graft dysfunction (r=-0.32, P > 0.05).

CONCLUSION

CAN was characterized by progressive injury to the renal microvasculature and the development of renal scarring. In particular, injury, angioregression and progressive loss of the PTC network strongly contributed to the development of interstitial fibrosis and graft dysfunction in CAN, and might play a crucial role in the development of CAN.

Enzyme-linked immunosorbent spot assay for donor-reactive interferon-gamma-producing cells identifies T-cell presensitization and correlates with graft function at 6 and 12 months in renal-transplant recipients

BACKGROUND

A major goal in clinical transplantation is the individualization of immunosuppression. This requires a definition of markers that identify patients at heightened risk of acute rejection and immune-mediated chronic allograft nephropathy.

METHODS

Frequencies of interferon-gamma-producing donor-reactive cells were serially determined in unselected renal-transplant patients in an enzyme-linked immunosorbent spot assay (ELISPOT) before transplantation (n = 42) and up to 10 (mean 5.0) times during the first 6 months posttransplantation (n = 48) to determine detailed kinetics and analyze for correlation with acute rejection and graft function at 6 and 12 months posttransplantation.

RESULTS

Pretransplant ELISPOT frequencies were significantly higher in patients with acute rejection (16/42) versus nonrejecters (26/42). Highly elevated pretransplant frequencies (>200 spots/300,000 peripheral blood mononuclear cells [PBMCs], n = 5/42) were associated with a risk of severe acute rejection episodes but were independent of risk factors such as high panel reactive antibodies. Early graft failure exclusively occurred in this group. Importantly, mean ELISPOT frequencies at weeks 2 and 3 but not at month 6 posttransplant correlated inversely with 6 and 12 months glomerular filtration rate. The correlation between ELISPOT frequencies and renal function showed the highest significance in patients without acute rejection.

CONCLUSIONS

The pretransplant ELISPOT assay might be useful to identify T-cell presensitized patients, who are at heightened risk for severe early acute rejection. An analysis of ELISPOT donor-reactive cells during the early posttransplant period might allow an identification of patients at risk for immune-mediated graft deterioration.