Rejection in single versus combined pancreas and kidney transplantation in pigs

Simultaneous combined transplantation: Intricacies in immunosuppression management

Simultaneous combined transplantation (SCT), i.e. the transplantation of two solid organs within the same procedure, can be required when the patients develop more than one end-stage organ failure. The development of SCT over the last 20 years could only be possible thanks to progress in the surgical techniques and in the perioperative management of patients in an ageing population. Performing such major transplant surgeries from the same donor, in a short amount of time, and in critical pathophysiological conditions, is often considered to be counterbalanced by the immune benefits expected from these interventions. However, SCT includes a wide array of different transplant combinations, with each time a different immunological constellation. Recent research offers new insights into the immune mechanisms involved in these different settings. Progress in the understanding of these immunological intricacies help to address the optimal induction and maintenance immunosuppressive treatment strategies. In this review, we summarize the different immunological benefits according to the type of SCT performed. We also incorporate the main outcomes according to the immunological risk at transplantation, and the deleterious impact of preformed or de novo donor-specific antibodies (DSA) in the different types of SCT. Finally, we propose comprehensive and evidence-based induction and maintenance immunosuppression strategies guided by the type of SCT.

[Pancreatic Transplantation: 2. Surgical technique and post-operative complications]

Since the first pancreatic allograft in 1966, pancreatic transplantations have been performed by numerous surgical teams throughout the world. Initial results were disappointing with a high percentage of technical failures and rejection. Over-optimistic enthusiasm for islet-cell allografts also retarded the development of pancreatic transplantation. Despite this slow start, results of pancreatic transplantation from 1995 onward have been very satisfactory and equivalent to or even better than the results of other solid organ transplants. This success has been due to better graft selection, improved surgical techniques and preservation solutions, and especially to improvements in immunosuppressive protocols. More than 19,000 pancreatic transplantations have now been performed throughout the world including both combined kidney-pancreas transplantations and pancreas-only transplantations. The most satisfactory results occur in the setting of dialysis-dependent renal failure due to diabetes; simultaneous combined kidney and pancreas transplantation is performed with the total pancreas implanted into the bowel and with venous drainage into the portal system. The long-term risks and constraints of chronic diabetes with renal failure must be weighed against the risks of a complex surgical procedure, significant post-operative complications, and the need for long-term immunosuppressive therapy.

Impact of acute rejection episodes on long-term graft survival following simultaneous kidney-pancreas transplantation

Although it is well established that acute rejection is one of the major risk factors for chronic graft loss following kidney transplantation, its effect on long-term graft survival following simultaneous kidney-pancreas transplants (SKPTs) is less well known. We analyzed a large cohort of SKPTs and cadaver kidney transplants reported to the United Network for Organ Sharing database during 1988-97, to determine the impact of acute rejection episodes on long-term kidney and pancreas graft survival. Only patients whose kidney and pancreas grafts had survived for at least 1 year were included. Other potential risk factors influencing long-term graft survival were included in the analysis. Of the 4251 SKPTs, 45% had no acute rejection, 36% had kidney only rejection, 3% had pancreas only rejection, and 16% had both kidney and pancreas rejection within the 1st year post transplant. The 5-year kidney and pancreas graft survival rates adjusted for other risk factors were 91% and 85%, respectively; for those with no acute rejection episodes, 88% and 84%, respectively; for those with kidney only rejection, 94% and 83%, respectively; for those with pancreas only rejection; and 86% and 78%, respectively, for those with both kidney and pancreas rejection. The relative risk (RR) of kidney graft failure was 1.32 when acute rejection involved the kidney graft only, while the RR was 1.53 when the rejection involved both organs. We conclude that acute rejection episodes have a negative impact on the long-term kidney graft survival in the SKPT population similar to that in the cadaver kidney transplant population. Patients who had acute rejection episodes of both kidney and pancreas have the worst long-term graft survival.

Anti-CD4 therapy in combined heart-kidney, heart-liver, and heart-small bowel allotransplants in high-responder rats

BACKGROUND

In these experiments, we studied the role of anti-CD4 (Ox38) monoclonal antibody in the induction of allograft unresponsiveness in high-responder Lewis rats in the single liver, kidney, small bowel, and heart versus the combined heart-kidney, heart-liver, and heart-small bowel transplantation models.

METHODS

ACI heart, kidney, liver, and small bowel allografts were transplanted into untreated and anti-CD4 treated Lewis rats. In selected animals bearing long-surviving ACI liver or kidney allografts for over 3 months, donor-matched second heart or third-party (Brown Norway) heart allografts were transplanted. Simultaneously, heart-liver, heart-kidney, and heart-small bowel transplants were performed on the day of operation. Rejected allografts were verified by autopsy and pathology.

RESULTS

ACI liver allografts were permanently accepted by Lewis recipients treated with either regular-dose (5 mg/kg for 4 days) or low-dose (5 mg/kg for 2 days) of anti-CD4 monoclonal antibody. Pretransplant anti-CD4 therapy (5 mg/kg for 4 days but not 5 mg/kg for 2 days) resulted in a long-term survival of kidney allografts (mean survival time [MST] > 100.0 days, n=5). Pretransplant anti-CD4 treatment (5 mg/kg for 4 days) could not induce tolerance when single ACI hearts were transplanted; however, long-term survival of ACI heart allografts could be induced when heart transplants were combined with liver (n=7) or kidney (n=8) transplants. The survival of both ACI heart allografts (MST=25.0 days, n=4) and small bowel allografts (MST=28.0 days, n=4) was also prolonged when simultaneous heart and small bowel transplantation was performed in anti-CD4-treated recipients. The second ACI heart allograft was permanently accepted by tolerant Lewis recipients of ACI liver or kidney allografts induced by anti-CD4 treatment, and third-party heart grafts were acutely rejected without affecting survival of the primary allografts.

CONCLUSION

Our current results show that: (1) there is a vigorous rejection of heart > or = small bowel > kidney > liver in high-responder Lewis rats after pretransplant anti-CD4 therapy; and (2) simultaneous or metachronous combined liver-heart and kidney-heart transplants may protect heart allografts from rejection.

Simultaneous pancreas and kidney transplant rejection: separate or synchronous events?

The results of simultaneous pancreas and kidney transplantation (SPK) cannot be matched by pancreas transplantation alone (PTA), in part because an independent diagnosis of pancreas graft rejection remains difficult. The relationship between rejection of the pancreas and rejection of the kidney is poorly understood, and it is not known whether simultaneous transplantation of both organs confers true protection to either graft. To study these questions, reliable canine allotransplant models of kidney transplantation alone (KTA), PTA, and SPK were established. Sixty-seven mongrel dogs received KTA (n=21), PTA (n=23), or SPK (n=23) with either no immunosuppression, low-dose cyclosporine (CsA)-based immunosuppression, or high-dose CsA-based immunosuppression. Needle core biopsy (NCB) and fine needle aspiration biopsy (FNAB) were performed at 0, 2, 4, 7, 9, 11, 14, 21, and 30 days or at the time of graft failure. Pancreas and kidney graft survival after SPK was significantly shorter in dogs given low-dose CsA than in dogs given high-dose CsA (pancreas, P<0.04; kidney, P<0.03). Concurrent NCBs and FNABs were performed on 227 occasions in pancreas grafts and 229 occasions in kidney grafts. The time to initial evidence of rejection by NCB was not different in any immunosuppressed group. Synchronous rejection occurred in 73% of immunosuppressed SPK biopsies. Kidney-only rejection occurred in 23% of biopsies and pancreas-only rejection occurred in only 3% after SPK. All markers of pancreas graft rejection were poor, with the most sensitive being NCB of the simultaneously transplanted kidney. In summary, recipients of SPK required more immunosuppression than recipients of PTA, and improved PTA survival should be achievable with more sensitive markers of rejection. Markers of kidney rejection were the most sensitive indicators of pancreas rejection, and independent pancreas rejection was uncommon after SPK.

Equivalent success of simultaneous pancreas kidney and solitary pancreas transplantation. A prospective trial of tacrolimus immunosuppression with percutaneous biopsy

OBJECTIVE

This study was designed to evaluate the results of solitary pancreas transplantation in a protocol that uses the new immunosuppressant tacrolimus (FK) and liberally applies ultrasound-guided percutaneous pancreas biopsy to diagnose rejection.

SUMMARY BACKGROUND DATA

Pancreas graft survival in patients who simultaneously receive a kidney transplant (SPK) historically has been 75% to 90% at 1 year, approaching that of cadaveric kidney transplantations. In sharp contrast, graft survival rates in patients who receive a pancreas atone (PA) have remained static over the past decade, with approximately 50% functional at 1 year. It was hypothesized that the results of PA transplantations would improve with newer maintenance immunosuppressants and biopsy techniques.

METHODS

Twenty-seven PA recipients prospectively were treated with FK-based immunosuppression (PA-FK). Percutaneous biopsy was performed for hyperamylasemia, hyperlipasemia, hypoamylasuria, or unexplained fever. One year pancreas graft survival in these patients was compared to 15 cyclosporine treated PA cases (PA-CsA) and 113 SPK recipients.

RESULTS

The 1-year pancreas graft survival rate of 90.1% in technically successful PA-FK patients was significantly better than the 53.4% rate in PA-CsA recipients (p = 0.002) and no different than the 87.4% rate in SPK recipients. The only graft lost to acute rejection in the PA-FK group was because of acknowledged patient noncompliance. Percutaneous biopsy substantially improved the diagnostic certainty in cases of suspected rejection and was associated with a low complication rate (3/178 = 1.5%).

CONCLUSIONS

Modern immunosuppression and biopsy techniques have improved the success of solitary pancreas transplantations to the point where outcome is now equivalent to that of SPKs.

Delayed endocrine pancreas graft function after simultaneous pancreas-kidney transplantation. Incidence, risk factors, and impact on long-term outcome

BACKGROUND

The incidence of delayed endocrine pancreas graft function and its impact on long-term outcome after simultaneous pancreas-kidney transplantation are unknown.

METHODS

We studied 54 technically successful adult type I insulin-dependent diabetic recipients of cadaver, whole organ, bladder-drained simultaneous pancreas-kidney transplants (mean age, 37.6 years; 65% male, 35% female; 9% pancreas retransplants; 63% on chronic pretransplant dialysis; mean duration of diabetes, 25.1 years). Insulin was administered during the first 2 weeks after transplantation, as needed, to keep blood glucose < 150 mg/dl. Delayed endocrine pancreas graft function was defined as total, cumulative insulin requirement of > 30 U between day 5 and day 10, and/or > 15 U between day 11 and 15. Quadruple immunosuppression was used for all recipients.

RESULTS

The incidence of delayed endocrine pancreas graft function was 69%. By univariate analysis, delayed endocrine graft function was associated with pretransplant recipient weight > 80 kg (P = 0.04), donor age > 45 years (P = 0.02), and cardiocerebrovascular (P = 0.06) and nontraumatic causes of donor death (P = 0.02). The incidence of acute pancreas rejection episodes was similar for recipients without and with delayed endocrine pancreas graft function. Pancreas graft survival at 1 and 3 years was 94% and 82% without versus 76% and 59% with delayed endocrine graft function (P = 0.03).

CONCLUSIONS

Increased pancreas graft failure after delayed endocrine function was a consequence of insufficient functional reserve (e.g., older donors) rather than increased immunogenicity. Pretransplant reduction of recipient weight and careful donor selection are therefore crucial in order to decrease the incidence of delayed endocrine pancreas graft function and its negative impact on long-term outcome.

Colon vs small bowel rejection after total bowel transplantation in a pig model

With the advent of FK 506, small bowel transplantation has become clinically feasible. Both clinically and experimentally, jejunal and ileal biopsies are used for early diagnosis of rejection. More recently, the colon, in addition to the small bowel, has been transplanted to decrease the high incidence of diarrhea after small bowel transplantation. A Bishop-Koop ileostomy allows biopsies on a regular basis, but the diagnosis of rejection remains a problem after takedown of the ileostomy. Rejection of the ileum is more frequent and more severe than rejection of the jejunum or the colon. Colon biopsy after ileostomy takedown would not rule out rejection of the ileum.

Experimental tracheal and tracheoesophageal allotransplantation. Paris-Sud University Lung Transplantation Group

We investigated the effects of allograft perfusion with a preservative technique and of combined thyrotracheoesophageal implantation on airway epithelium of long segments of thyrotracheal grafts allotransplanted on their own vascular pedicles into immunosuppressed pigs. Four groups of five animals each underwent heterotopic (into the neck) thyrotracheal (group 1) and thyrotracheoesophageal (group 2) and orthotopic thyrotracheal (group 3) and thyrotracheoesophageal (group 4) allotransplantation. Allograft revascularization included (1) interposition of donor right subclavian artery--incorporating the inferior thyroid artery--to recipient right carotid artery (end-to-end fashion) and (2) end-to-side anastomosis of donor anterior vena cava to recipient right external jugular vein. All thyrotracheoesophageal blocks were harvested after inferior thyroid artery perfusion with 4 degrees C Euro-Collins solution. The overall lengths of tracheal and esophageal grafts were 10.7 +/- 2.7 cm and 13.4 +/- 3.6 cm, respectively. In the heterotopic groups, all allografts were viable and histologically normal at postmortem examination and the incidence and severity of airway ischemia and rejections (at equal residual levels of cyclosporine) were not different between groups 1 and 2. In the orthotopic groups, the first two pigs died of airway collapse with histologically normal grafts. In the remaining pigs, temporary airway stenting was inserted and allografts remained viable and histologically intact for their entire length 30 days after transplantation. Transplanted tracheal smooth muscles had concentration-dependent contractions and relaxations similar to those of nontransplanted (native) tracheas. This study documents the feasibility of allotransplanting long tracheal and esophageal segments on their own vascular pedicles and demonstrates that allograft preservation and thyrotracheoesophageal transplantation are equally effective in minimizing airway ischemia. Thyrotracheoesophageal transplantation does not enhance recipient alloimmune response compared with thyrotracheal transplantation alone.

Tissue-specific effects of anti-CD4 therapy in induction of allograft unresponsiveness in high and low responder rats

In these experiments, we studied the role of anti-CD4 (Ox38) monoclonal antibody in the prevention of heart and/or kidney allograft rejection in low (ACI) and high (Lewis) responder rats. In low responder ACI rats, donor-specific tolerance for heart and kidney allografts (individually or in combination) was achieved by pretransplant anti-CD4 therapy. In high responder Lewis rats, anti-CD4 therapy alone (or combined with anti-CD8 (Ox8), thymectomy or total lymphoid irradiation) did not prevent first-set rejection of heart allografts. This difference was correlated with a more profound and longer lasting CD4+ cell depletion in the low responder strain. Anti-CD4 treatment, however, produced tolerance of kidney transplants in high responder rats. Additionally, anti-CD4 treatment induced tolerance to heart (as well as kidney) allografts in Lewis recipients of combined kidney and heart allografts from ACI. The effects of anti-CD4 treatment thus depend upon the recipient responder status as well as the organs transplanted and the order of transplantation.