Immunomodulatory effect of extracorporeal photopheresis after successful treatment of resistant renal allograft rejection

BACKGROUND

Acute renal allograft rejection contributes to patient morbidity. Standard immunosuppressives are only partially effective and have significant side effects. Extracorporeal photopheresis (ECP) has been effective in reversing the acute rejection process. T cell cytokine expression is implicated in rejection and tolerance but actual changes in the cytokine profile of ECP-treated individuals have not been documented.

METHODS

ECP was administered to a patient with acute renal allograft rejection resistant to other immunosuppressives. Enzyme-linked immunosorbent spot (ELISPOT) assay was performed to determine the frequency of mitogen-induced cytokine-producing cells before and after ECP.

RESULTS

ECP resulted in resolution of rejection; serum creatinine concentration fell from 7.1 to 2.2 mg/dl; ELISPOT revealed a three-fold increase in the frequency of IL-5 producing cells; IFN-gamma:IL-5 ratio shifted from 2.73 pre-treatment to 1.01 post-treatment.

CONCLUSION

Effective therapy of acute allograft rejection with ECP alters the peripheral blood cytokine profile towards "type 2" cytokines, suggesting that alteration of T cell cytokine profiles may contribute to the resolution of the process.

Elevated endothelin-1 in tubular epithelium is associated with renal allograft rejection

Vascular endothelin-1 (ET-1) levels are elevated in patients with renal allograft rejection, and the mitogenic and pressor actions of ET-1 might contribute to transplant vasculopathy, posttransplantation hypertension, and ischemia-reperfusion injury. In contrast, relatively little is known about tubular expression of ET-1 in acute or chronic rejection of renal allografts. We sought to determine whether tubular ET-1 levels were altered in patients with acute or chronic renal allograft rejection. Immunohistochemical analysis of tubular ET-1 was performed in renal biopsy specimens from 18 patients with acute rejection, 7 patients with chronic rejection, and 5 normal kidneys excised for localized neoplasm. The diagnosis of acute or chronic rejection in each patient was verified and graded using the Banff schema. Renal tubular epithelium from patients with allograft rejection had markedly elevated staining for ET-1 compared with normal kidneys. Tubular ET-1 levels were elevated in 18 of 18 patients with acute rejection and 5 of 7 patients with chronic rejection. Tubular ET-1 staining was graded from 0 to +3 as follows: normal kidneys, 1.2 +/- 0.2; acute rejection, 2.3 +/- 0.4 (P < 0.01); and chronic rejection, 2.2 +/- 0.5 (P < 0.01). ET-1 staining was prominent in both proximal and distal tubules, and we observed abundant ET-1 secretion from proximal tubular epithelium in culture. Moreover, ET-1 activated the c-fos immediate early gene promoter in proximal tubular cells transfected with a c-fos luciferase reporter. We conclude that elevated tubular ET-1 levels are associated with acute and chronic rejection of renal allografts. Our results also suggest distinct pathophysiological roles for the tubular and vascular ET-1 systems in renal allograft rejection.

Hypertension after pancreas-kidney transplantation: role of bladder versus enteric pancreatic drainage

BACKGROUND

Recent reports suggest that hypertension may be less common after simultaneous pancreas-kidney transplantation than after kidney transplantation alone. However, the mechanisms for this beneficial effect have not been delineated. We hypothesize that lower blood pressures may result from chronic volume depletion in patients with bladder-drained pancreatic allografts.

METHODS

We compared the incidence and severity of hypertension 12 months after transplantation in 79 bladder-drained pancreas-kidney recipients and 46 diabetic kidney-only recipients. These two groups were compared with a smaller group of enterically drained pancreas-kidney recipients. Blood pressure was also compared before and after surgical conversion from bladder to enteric drainage in 10 patients.

RESULTS

Hypertension was significantly less common and less severe after pancreas-kidney transplantation than after kidney transplantation alone, but the benefit of the pancreas transplant was evident only in bladder-drained patients. Logistic regression analysis of the bladder-drained pancreas-kidney patients confirmed the independent impact of the pancreatic allograft on the presence of hypertension, indicated an independent association with serum creatinine concentration and donor age, but suggested no correlation with recipient age, race, or number of rejection episodes. A comparison of blood pressures before and after pancreatic conversion from bladder to enteric drainage indicated no significant change in the prevalence or severity of hypertension.

CONCLUSIONS

We conclude that the beneficial effect of a pancreas transplant on the prevalence and severity of hypertension after simultaneous pancreas-kidney transplantation is limited to bladder-drained patients. Although it is possible that the effect is mediated by chronic volume depletion, the observation that blood pressure does not increase after conversion from bladder to enteric drainage suggests that other factors may be involved.

Kidney-pancreas transplantation for diabetic nephropathy

Pancreas transplantation is being performed with increasing frequency and increasing technical success. The availability of new immunosuppressant agents has been associated with a reduction in the previously high rates of allograft rejection in recipients of simultaneous pancreas-kidney transplants. These lower rejection rates have, in turn, led to changes in surgical techniques and a resurgence of interest in isolated pancreas transplantation--either in nonuremic patients or, more commonly, in patients who have already received a prior kidney transplant. Pancreas transplantation has emerged as an important option for the management of patients with type I diabetes mellitus and diabetic nephropathy.

Pretransplant Frequency of Donor-Specific, IFN-γ-Producing Lymphocytes Is a Manifestation of Immunologic Memory and Correlates with the Risk of Posttransplant Rejection Episodes

While matching for MHC Ags improves renal allograft survival, closely matched grafts sometimes fail due to rejection, and poorly matched allografts are often well tolerated by the recipient. The severity of the rejection process may partially depend on the presence of environmentally primed T cells in the recipient that cross-react with donor Ags. To test for the presence of primed, donor-specific T cells in humans before transplantation, we used an enzyme-linked immunospot assay for detection of allospecific cytokines produced by individual human PBLs. We demonstrate that this approach detects cytokine production at single cell resolution and detects production of IFN-γ only when there is defined immunologic priming, thus representing a measure of primed donor-specific immunity. Because the environmental Ag exposure of the recipient is not a function of the HLA mismatch between donor and potential recipient, the number of HLA mismatches may not correlate with the frequency of pretransplant, donor-specific IFN-γ-producing PBLs. Studies of donor-specific IFN-γ-producing lymphocytes in a cohort of patients being evaluated for renal transplantation corroborated this hypothesis. Moreover, for recipients of both living and cadaver renal allografts, the pretransplant frequency of donor-specific memory cells correlated with the posttransplant risk of developing acute rejection episodes. This improved ability to define the strength of the allospecific immune response by enzyme-linked immunospot assay may allow improved pairing of recipients with donors and identification of kidney allograft donor-recipient pairs at high risk for acute rejection, thus permitting targeted interventions aimed at prolonging graft survival.

Pretransplant frequency of donor-specific, IFN-gamma-producing lymphocytes is a manifestation of immunologic memory and correlates with the risk of posttransplant rejection episodes

While matching for MHC Ags improves renal allograft survival, closely matched grafts sometimes fail due to rejection, and poorly matched allografts are often well tolerated by the recipient. The severity of the rejection process may partially depend on the presence of environmentally primed T cells in the recipient that cross-react with donor Ags. To test for the presence of primed, donor-specific T cells in humans before transplantation, we used an enzyme-linked immunospot assay for detection of allospecific cytokines produced by individual human PBLs. We demonstrate that this approach detects cytokine production at single cell resolution and detects production of IFN-gamma only when there is defined immunologic priming, thus representing a measure of primed donor-specific immunity. Because the environmental Ag exposure of the recipient is not a function of the HLA mismatch between donor and potential recipient, the number of HLA mismatches may not correlate with the frequency of pretransplant, donor-specific IFN-gamma-producing PBLs. Studies of donor-specific IFN-gamma-producing lymphocytes in a cohort of patients being evaluated for renal transplantation corroborated this hypothesis. Moreover, for recipients of both living and cadaver renal allografts, the pretransplant frequency of donor-specific memory cells correlated with the posttransplant risk of developing acute rejection episodes. This improved ability to define the strength of the allospecific immune response by enzyme-linked immunospot assay may allow improved pairing of recipients with donors and identification of kidney allograft donor-recipient pairs at high risk for acute rejection, thus permitting targeted interventions aimed at prolonging graft survival.

Inhibition of endothelin-converting enzyme attenuates transplant vasculopathy and rejection in rat cardiac allografts

BACKGROUND

Transplant vasculopathy in kidney and heart allografts is associated with marked elevation of endothelin-1 (ET-1), but a role for ET-1 in the pathogenesis of transplant vasculopathy and chronic rejection has not been established. We, therefore, tested whether inhibition of ET-1-converting enzyme by phosphoramidon (PA) would attenuate rejection in a rat model of chronic cardiac allograft rejection (Lewis [LEW] to F344).

METHODS

Donor LEW rats were pretreated 24 hr before transplantation with a bolus injection of vehicle (water) or PA. Twenty- four hour after transplantation, water or PA was continuously administered through an osmotic mini-pump. Plasma ET-1 levels in Fisher 344 (F344) recipients were 0.8+/-0.1 pg/ml in water-treated rats and 0.2+/-0.2 pg/ml (P<0.01) in PA-treated rats, demonstrating that the PA treatment protocol effectively lowered ET-1 biosynthesis.

RESULTS

LEW cardiac allografts treated with water survived (i.e., palpable heart beat) for 16.0+/-0.5 days (n=6). Inhibition of ET-1 secretion by PA improved allograft survival to 28.8+/-3.3 days (P<0.01, n=8). An analysis of cardiac arteries demonstrated that PA treatment attenuated transplant vasculopathy. A morphometric scale of neointima formation (0-5) was 1.4+/-0.2 and 3.6+/-0.2 in PA- or water-treated rats, respectively (P<0.01). The percent of luminal occlusion, as measured by microscopic image analysis, was 19+/-6% in PA-treated animals and 38+/-6% (P<0.01) in animals treated with water. PA treatment also reduced infiltration of ED-1-positive monocytes/macrophages into the vascular neointima.

CONCLUSIONS

We conclude that, even in the absence of concomitant immunosuppression, inhibition of ET-1 biosynthesis significantly attenuates transplant vasculopathy and improves survival of LEW to F344 cardiac allografts.

Incidence and long-term cost of steroid-related side effects after renal transplantation

Corticosteroids are an essential component of most immunosuppressive regimens currently used in renal transplantation because of their efficacy in reducing acute rejection and improving graft survival. Steroids, however, are associated with numerous side effects that lead to increased patient morbidity and mortality. The incidence and economic cost of steroid-related side effects have not been quantitatively assessed. Thus, based on a systematic review of the published literature, we estimated the incidence of steroid-related hypertension (15%), posttransplantation diabetes mellitus (10%), peripheral fractures (2% per year), avascular necrosis of the hip (8%), and cataracts (22%). In addition, we estimated that approximately 5% of patients who have cataracts or avascular necrosis of the hip require surgery. We used these literature-based estimates in a model to project the costs of treating side effects over a 10-year posttransplantation time frame for a 50-patient cohort that represented an average-sized renal transplant center. Steroid-induced hypertension and its complications were the most expensive side effect ($93,900), followed closely by posttransplantation diabetes ($89,700) and avascular necrosis of the hip ($61,700). Cataracts and peripheral bone fractures were less costly ($16,300 and $4,300, respectively). The cumulative projected 10-year cost of all side effects for the 50-patient cohort was $265, 900, or $5,300 per transplant patient. Steroid-related side effects add to the long-term cost of medical care of renal transplant recipients. These costs provide a rationale for further investigation of steroid-sparing immunosuppression protocols.

Azathioprine monotherapy in HLA-identical live donor kidney transplant recipients

The high success rate of HLA-identical sibling transplants and our previous experience with steroid-free immunosuppressive regimens and cyclosporine withdrawal prompted us to evaluate the safety and efficacy of monotherapy with azathioprine in 12 HLA-identical kidney transplant recipients with a serum creatinine concentration less than 176.8 mumol/L, a 1-way stimulatory index less than 2.0 in a post-transplant mixed lymphocyte culture, and a demonstrated tolerance of a minimum azathioprine dose of 1.0 mg/kg per day without leukopenia. Eleven of 12 patients were successfully converted to azathioprine monotherapy without a significant change in serum creatinine concentration for as long as 76 months. Benefits of steroid and cyclosporine withdrawal included a significant reduction in mean systolic and diastolic blood pressure, number of blood pressure medications, total serum cholesterol, and glycohemoglobin in diabetic subjects. Our results suggest that azathioprine monotherapy is safe and effective in a select group of HLA-identical sibling transplants, but these benefits must be carefully balanced against an associated risk of precipitating acute allograft rejection.

Benefits of pre-emptive dose reduction for Sandimmune to Neoral conversion in stable renal transplant recipients

In an effort to minimize nephrotoxicity resulting from greater exposure to cyclosporine after Sandimmune to Neoral conversion, we compared two conversion regimens using different dosing ratios. Serial serum creatinine concentrations and trough cyclosporine levels were measured in 26 patients converted from Sandimmune to Neoral using a 1:0.8 dosing ratio (Group 1) and compared to those of 26 patients converted using a 1:1 dosing ratio (Group 2). The percentage change in peak serum creatinine concentration after conversion was greater in Group 2. However, at last follow-up, the dose reductions in each group were comparable. Following conversion, patients in Group 1 required fewer dose adjustments and follow-up blood tests. Compared to conversion using a 1:1 dosing ratio, conversion from Sandimmune to Neoral using a 1:0.8 ratio results in comparable dose reductions and less short-term nephrotoxicity, while requiring less frequent laboratory monitoring.

Elevated neointimal endothelin-1 in transplantation-associated arteriosclerosis of renal allograft recipients

BACKGROUND

Chronic renal allograft rejection is characterized histologically by transplantation-associated arteriosclerosis and glomerulosclerosis (Tx-AA and Tx-AGS). Recent studies in animal models implicate the mitogenic and pressor actions of endothelin-1 (ET-1) in Tx-AA. In humans, however, a link between elevated ET-1 secretion and Tx-AA or Tx-AGS remains unclear. In this study we analyzed expression of ET-1 in the vasculature of renal transplant patients with chronic or acute rejection and in normal controls.

METHODS

Renal vascular and glomerular ET-1 was assessed by immunohistochemistry in 12 patients with clinically and histologically defined chronic rejection, in 11 patients with acute rejection, and in 5 normal kidneys. ET-1 staining was also correlated with various clinical parameters and with a morphometric index of neointima formation. ET-1 secretion was measured by ELISA in cultured human vascular cell types treated with T cell- and macrophage-associated cytokines.

RESULTS

We found that renal allografts with chronic rejection and Tx-AA expressed 6.1-fold more ET-1 in the vasculature relative to allografts with acute rejection or to normal kidneys (P < 0.01). In Tx-AA, ET-1 was detected predominantly in the neointima, which contained mostly endothelial cells and smooth muscle cells. A strong positive correlation (r = 0.82, P < 0.01) was observed between vascular ET-1 peptide expression and hypertension in patients with chronic rejection. We also showed that macrophage-associated cytokines, but not T cell-associated cytokines, stimulated ET-1 secretion in human endothelial cells, vascular smooth muscle and mesangial cells.

CONCLUSIONS

These results demonstrate that elevated ET-1 in the neointima is associated with Tx-AA and chronic rejection. In addition, these results point to an important role for endothelial dysfunction in chronic renal allograft rejection.

Withdrawal of immunosuppression: implications for composite tissue allograft transplantation

Complete or partial withdrawal of immunosuppression is a desirable goal for physicians managing solid organ transplant recipients and has particular appeal for the management of composite tissue allograft recipients. Experience to date with steroid withdrawal or cyclosporine withdrawal in organ transplant recipients suggests that the risks of acute rejection are minimized with slow tapering of the drugs and when drug withdrawal is attempted many months or years after transplantation. Unfortunately, the full benefits of withdrawing any component of a multidrug immunosuppression regimen can probably be achieved only when the drug is withdrawn relatively early after transplantation. Thus, there is a need for improved immunologic monitoring to facilitate withdrawal of immunosuppression in any setting. Because steroid withdrawal might be particularly advantageous to the recipient of a composite tissue allograft, further experience is needed to determine the safety of steroid withdrawal with newer immunosuppressants such as tacrolimus, mycophenolate mofetil, and sirolimus.

Resolution of hepatitis B viremia in a renal transplant recipient treated with alpha-2b interferon

A renal transplant patient developed symptomatic hepatitis after withdrawal from corticosteroids. Tests for hepatitis B e antigen and hepatitis B viral DNA were both positive prior to treatment with 1 million units alpha interferon three times weekly for 3 weeks followed by an increase to 3 million units alpha interferon three times weekly for a total of 16 weeks. At the end of treatment, hepatitis had clinically resolved with conversion to a hepatitis B e antibody positive and hepatitis B e antigen and viral DNA negative state. The renal allograft function remained excellent throughout the course of therapy with interferon.

Enzyme-linked immunosorbent assay spot detection of interferon-gamma and interleukin 5-producing cells as a predictive marker for renal allograft failure

BACKGROUND

Despite improvements in the short-term survival of renal transplants, many allografts fail over the 5-10 years after transplantation. We sought to identify an immunologic assay that could identify those patients at high risk for future allograft failure.

METHODS

Blood samples were obtained from 23 renal allograft recipients with acute and/or chronic graft dysfunction and from 22 controls. Isolated peripheral blood lymphocytes (PBLs) were tested for interferon (IFN)-gamma and interleukin (IL)-5 production using an enzyme-linked immunosorbent spot assay. IFN-gamma:IL-5 ratios were calculated and compared between groups. Among the 23 patients with graft dysfunction, the ratios were also compared with graft function at 6 months.

RESULTS

IFN-gamma:IL-5 ratios of > or = 15 were associated with allograft rejection episodes in 8 of 12 cases, whereas 10 of 11 episodes of graft dysfunction from other causes (infection, drug toxicity, obstruction) were associated with values <15. All normal controls had values <15 (22/22). Among the graft recipients with acute renal failure, all patients with IFN-gamma:IL-5 ratios <15 exhibited improved renal function at 6-month follow-up (14/14), whereas 8 of 9 patients with IFN-gamma:IL-5 ratios > or = 15 developed allograft failure at 6 months (sensitivity 100%, specificity 93.3%).

CONCLUSION

In renal transplant recipients with acute allograft dysfunction, mitogen-induced peripheral blood lymphocyte IFN-gamma:IL-5 ratios > or = 15 were highly predictive of allograft failure within 6 months of the assay. This test may be a useful prognostic marker for identification of transplant recipients with acute graft dysfunction who are at high risk for future graft loss and thus allow targeted therapeutic interventions to prolong graft survival.

Free pentosidine and neopterin as markers of progression rate in diabetic nephropathy. Collaborative Study Group

BACKGROUND

Patients with diabetic nephropathy experience a progressive and usually inexorable decline in renal function. The presence of the structurally defined advanced glycation end product (AGE) pentosidine on tissue and circulating proteins has been correlated with the severity of diabetic complications.

METHODS

To delineate a role for this AGE in the progression of diabetic nephropathy, glycohemoglobin and free and protein-bound pentosidine were measured in baseline stored serum and urine from a subgroup of patients with diabetes mellitus and proteinuria originally followed by the Collaborative Study Group Trial. To delineate a potential role for an immune-activation response to AGEs, the inflammatory markers, interleukin-6 (IL-6), C-reactive protein (CRP), and the monocyte activation marker marker neopterin were also measured at baseline. The patients chosen represented 67 subjects whose creatinine levels had "doubled" over the course of the study whether or not they later were treated with captopril, and 67 paired "non-doublers."

RESULTS

Baseline disease activity, as manifested by glycohemoglobin, serum creatinine and degree of proteinuria was equal in the two groups, as was protein-bound pentosidine and the immune-markers IL-6 and CRP. At baseline the "doublers" as compared to the "non-doublers" had elevated serum levels of free pentosidine and neopterin. Baseline increases in these two parameters were also associated with an increased rate of "doubling" of serum creatinine by the proportional hazards method.

CONCLUSION

Differences in individual responsiveness to AGEs, as manifested by either the production of free pentosidine or its release from a protein-bound form, and by evidence of monocyte/macrophage activation, are associated with progression of diabetic nephropathy.

Steroid withdrawal in renal transplant recipients: pro point of view

Steroid-free immunosuppression remains an attractive goal in an era in which the transplant community should be promoting long-term allograft survival by reducing cardiovascular risk and maximizing long-term patient survival. In the cyclosporine era, the risks of steroid withdrawal outweighed the benefits of steroid withdrawal in a substantial minority of patients. A number of new immunosuppressants may prove to be more steroid sparing than cyclosporine alone and promise to increase the safety of steroid-free immunosuppression for renal transplant recipients.