Total orthotopic small bowel allotransplantation in the dog. Features of atypical rejection and graft-versus-host reaction

The critical histologic review of our experience with small bowel allotransplantation in the dog is presented. While "classical" rejection with dense small cell infiltration and mucosal destruction does occur, more common is the "atypical" rejection reaction in which cellular infiltration is sparse. This "atypical" rejection was characterized by a significant decrease of mucosal epithelial structures with increased mitotic figures in crypt cells and frequent vascular changes, including segmental fibrinoid necrosis and thrombosis with or without overlying mucosal destruction. Substantial regenerating capacity of bowel mucosa tends to compensate for the destruction, complicating the histology. The host lymph nodes and spleen present a histologic picture highly suggestive of GVH reaction. The reduction in host lymphocytes in these organs from karyorrhexis with replacement by histiocytes and subsequently by plasma cells is described. It is emphasized that rejection and GVH are not mutually exclusive and occur simultaneously. The decrease of functional mucosal mass could well account for the nutritional malsequelae. Also, the weakening of immune structures on the host and the graft side may predispose to catastrophic enterogenous infections, perhaps explaining the large number of animals that die without overt signs of rejection following small bowel transplantation.     

Limb allotransplantation in rats: combined immunosuppression by FK-506 and 15-deoxyspergualin.

The immunosuppressive effect of combined therapy using FK-506 and 15-deoxyspergualin was investigated in rat limb allotransplantation. The right hindlimb of an inbred Dark Agouti rat (RT1a) was transplanted to a Lewis rat (RT1l) and observed for 120 days. Eighty-eight transplantations were performed. Rejection of the grafts was evaluated histologically as well as macroscopically. A pathologic grading system was used to rate the severity of rejection. Limb survival time in Lewis rats receiving FK-506 therapy for days was significantly prolonged by combined therapy with 15-deoxyspergualin. Histologic study showed practically no rejection in all the graft-composing tissues except the skin and bone marrow, in which there was rejection. These results suggest that tissues like bone, cartilage, and muscle may survive transplantation with short-term combination FK-506 and 15-deoxyspergualin therapy even after withdrawal of both agents.     

Induction of graft-versus-host disease by small intestinal allotransplantation in rats

Adult male (LewisXBrown Norway) F1 (LBNF1) rats received heterotopic small intestinal transplants from Lewis donors. Lewis-to-Lewis and LBNF1-to-LBNF1 isografts served as controls. All of the allograft recipients died after a median survival time of 16.2 days, but all isografted rats survived indefinitely. During the period of deterioration, allografted rats developed marked cutaneous erythema and became increasingly weak and cachectic. Histological changes of the skin, spleen, and grafts were characteristic of graft-versus-host disease (GVHD). There was a marked degree of relative splenomegaly. Injection of spleen cells obtained from LBNF1 rats with clinical GVHD into the foot-pad of syngeneic LBNF1 rats resulted in significant enlargement of the ipsilateral popliteal lymph node. The degree of lymph node enlargement was comparable to that induced in LBNF1 rats by injection of normal Lewis spleen cells. These results clearly demonstrate the ability of the small intestinal allograft to cause rapid and fatal GVHD in rats that are incapable of graft rejection.     

FK778 and FK506 combination therapy to control acute rejection after rat liver allotransplantation

BACKGROUND: In organ transplantation, several immunosuppressants are currently used to control graft rejection. Clinically, no single immunosuppressive agent can completely prevent posttransplantation immunoreaction; thus, combination therapy is usually performed. Novel agents with more powerful immunosuppressive activity and less toxicity need to be developed. METHODS: Lewis rat livers were orthotopically transplanted into Brown-Norway recipients. FK778 was administered orally from day 0 to day 6 to prevent acute rejection and from day 7 to day 13 to rescue ongoing rejection. To assess the combined effects, recipients were treated with intramuscular injection of FK506 and oral administration of FK778 from day 0 to day 6. Blood chemistry and histopathologic findings were measured to determine the patient's general condition and the graft condition. Allospecific antibodies were measured using enzyme-linked immunosorbent assays. The FK778 trough concentration was examined by using high-performance liquid chromatography. RESULTS: The acute immune response was suppressed by FK778 alone in a dose-dependent manner. The optimal FK778 dosage was determined to be 20 mg/kg per day, because adverse effects (weight loss and intestinal bleeding) occurred at 30 mg/kg per day. FK778 treatment from day 7 to day 13 rescued liver grafts from ongoing rejection. The intramuscular FK506 (0.125 mg/kg per day) injection and the oral FK778 (20 mg/kg per day) gavages suppressed acute liver graft rejection effectively and maintained better graft condition compared with monotherapy. CONCLUSIONS.: FK778 treatment effectively prevented acute rejection and rescued ongoing rejection after liver transplantation. The optimal dosage was determined to be 20 mg/kg per day. Combination therapy with FK506 was more beneficial than FK778 monotherapy.     

A schema for histologic grading of small intestine allograft acute rejection

BACKGROUND: Histologic evaluation of small bowel allograft biopsies is important for the diagnosis of acute rejection. However, a standard histologic schema to grade the severity of intestinal acute rejection is not currently available. The primary goal of this study was to develop a histologic grading system for the diagnosis of small bowel allograft acute rejection. METHODS: We evaluated 3268 small bowel allograft biopsies obtained from adult patients who underwent small bowel transplantation at the University of Pittsburgh Medical Center between 1990 and 1999. A histologic grading system was proposed and validated by retrospective correlation with clinical outcomes. RESULTS: Among the 3268 biopsies, 180 acute rejection episodes were diagnosed (88 indeterminate, 74 mild, 14 moderate, and 4 severe). All four histologically diagnosed, severe acute rejection episodes resulted in graft failure before resolution, despite aggressive immunosuppressive therapy. Four of the 14 moderate acute rejection episodes were associated with unfavorable clinical outcomes. In contrast, the 74 mild and 88 indeterminate acute rejection episodes were not associated with unfavorable clinical outcomes. Statistical analysis for trend revealed that grades indicating more severe acute rejection episodes were associated with a greater probability of unfavorable outcomes (P<0.01). In addition, there was good overall agreement among different pathologists regarding the diagnosis of acute rejection using the proposed schema, suggesting that this system is practical. CONCLUSIONS: This study provides a reliable predictive schema for assessment of the severity of human small bowel acute rejection.     

Induction of graft-versus-host disease and rejection by sensitized small bowel allografts

This study was undertaken to investigate under which circumstances graft versus host disease occurs following fully allogenic small bowel transplantation in the rat. To facilitate the development of GVHD, Brown-Norway donors were specifically sensitized against the Lewis hosts prior to transplantation. Additionally, the Lewis recipients were immunocompromised before transplantation using splenectomy, cyclosporine, and antilymphocyte serum. No further immunosuppressive therapy was administered after transplantation. When all pretreatment regimens were used, acute lethal GVHD arose in two of nine animals (22%), whereas in two animals (22%) signs of acute GVHD and rejection were observed concurrently. When recipients of sensitized grafts were pretreated with CsA alone, one of eight animals (12.5%) showed signs of GVHD and rejection. All other animals died of acute rejection without clinical signs of acute GVHD. However, histological signs of GVHD were observed frequently in hosts grafted with a sensitized small bowel transplant. These data show that acute lethal GVHD can occur when an immunocompromised host is grafted with a sensitized intestinal transplant.     

FK 506 reverses acute graft-versus-host disease after allogeneic bone marrow transplantation in rats.

Severe graft-versus-host disease was induced by transplantation of ACI rat bone marrow and spleen cells into irradiated Lewis rat recipients. Treatment with FK 506 or cyclosporine A (CsA) was started after clinical and histologic evidence of acute GVHD was present. A 14-day course of FK 506 at 1.0 mg/kg/day could rescue 100% of the animals suffering from GVHD. In contrast only one half of the animals treated with CsA at a high dose of 25 mg/kg/day recovered. After cessation of immunosuppressive therapy, FK 506-treated animals displayed a marked prolonged disease-free interval as compared to CsA-treated bone marrow recipients. Recurrence of the disease in these animals could be prevented when FK 506 treatment was continued after the induction period with a low maintenance dose of 0.1 mg/kg/day every other day.     

The use of FK506 and RS61443 for reversal of small-bowel rejection

Successful clinical small-bowel transplantation is still difficult to achieve [3, 6]. Two features render the small intestine unique among vascularised solid organ grafts. First, the bowel contains a large amount of lymphoid tissue within the Peyer's patches, mesenteric lymph nodes, and intraepithelial lymphocytes, which are thought to mediate graft-versus-host disease and provide a major stimulus for the recipient's immune system [10]. Unfortunately, mere surgical reduction of these tissues, by using segmental allografts, does not furnish any immunological advantage [12]. Second, the small bowel lacks specific serum markers such as blood urea nitrogen (BUN) in the kidney or bilirubin in liver transplantation. Clinical signs such as fever, pain, or tenderness of the abdomen may indicate an already advanced destruction of the graft. Therefore, very potent immunosuppressive regimens are necessary to avoid small-bowel allograft rejection or even to reverse an ongoing rejection process. Cyclosporin was shown in small and large animal models to control rejection reactions sufficiently [4, 13]. However, there are two even more promising immunosuppressive agents currently under investigation. FK506, a macrolide lactone isolated from Streptomyces tsukubaensis, leads to long-term survival of small-bowel allografts in a rodent model and has already been used in a few clinical small-bowel transplantations [11, 14]. RS61443, a mycophenolic acid morpholinoethylester, selectively inhibits T- and B-cell proliferation [9]. We have investigated the use of FK506 and RS61443 for the reversal of small-bowel allograft rejection in a small animal model.     

Upfront use of eculizumab to treat early acute antibody-mediated rejection after kidney allotransplantation and relevance for xenotransplantation

Acute antibody-mediated rejection (AMR) early after transplant remains a challenge, both in allotransplantation and in xenotransplantation. We report the case of an early and severe acute AMR episode in a kidney transplant recipient that was successfully treated with upfront eculizumab. A 58-year-old woman had been on dialysis since 2014. She underwent a first kidney transplant in 2018 with primary non-function and received several blood transfusions. Postoperatively, she developed anti-HLA antibodies. One year later, she received a second allograft from a deceased donor. At day 0, there was only one preformed low-level donor-specific antibody (DSA) anti-DQ7. After initial excellent allograft function, serum creatinine increased on days 7-9, and this was associated with oligo-anuria. On day 7, there was an increase in her DSA anti-DQ7 and 4 de novo DSA had developed at high MFI values. Allograft biopsy showed severe active AMR with diffuse C4d deposits in peritubular capillaries. The early acute AMR episode was treated with upfront eculizumab administration (2 doses) with efficient CH50 blockade (< 10% CH50). Rituximab was also administered on day 12, and intravenous immunoglobulin (IVIG) was given over the following days. There was an excellent clinical response to eculizumab administration. Eculizumab administration rapidly reversed the acute AMR episode without the need for plasmapheresis. Rituximab and IVIG were also used as B-cell immunomodulators to decrease DSA. Blocking efficiently the terminal complement pathway may become a useful strategy to treat acute AMR in sensitized recipients of allografts, and possibly in recipients of discordant xenografts.     

rhIL-10抑制小肠移植急性排斥反应的研究

目的观察rhIL-10对小肠移植急性排斥反应和T细胞增殖的抑制作用。方法将移植后的大鼠随机分为同基因组、对照组和3种不同剂量的rhIL-10治疗组，各组n=6。术后3、5、7d取移植肠管，行病理检查，测外周血T细胞亚群及术后7d肝、肾功能的重要参数：天冬酸氨基转移酶（AST）、丙氨酸氨基转移酶（ALT）、血肌酐（Crea）和血尿素（BUN）。结果对照组术后3d发生轻度排斥，5d发生中度排斥，7d发生重度排斥；中、高剂量组除部分标本在术后5、7d发生轻度排斥外，无排斥征象；低剂量组与对照组改变相似，但排斥的病理改变发生较晚、较轻。术后3、5、7d，低、中、高剂量组外周血CD3^＋T细胞数及CD4^＋／CD8^＋比值与对照组比较差异有统计学意义（P〈0．05）。各组AST、ALT、Crea和BUN差异均无统计学意义（P〉0．05）。结论（1）对小肠移植急性排斥的抑制，低剂量作用是明确的，但疗效有限。中、高剂量作用较明显；与同基因组、对照组比较，不增加肝、肾毒副作用；（2）动态检测外周血CD3^＋T细胞数及CD4^＋／CD8^＋比值可作为器官移植术后监测排斥反应的重要指标之一。     

Monoclonal antibodies for the prevention of graft-versus-host disease and marrow graft rejection. The depletion of T cell subsets in vitro and in vivo

One of the major complications of allogeneic bone marrow transplantation is graft-versus-host disease. This can be avoided by removing the mature T cells from the marrow, most conveniently by the use of monoclonal antibodies. However, T cell purging results in an increased tendency for the recipient to reject the donor marrow. We have developed monoclonal antibodies to L3/T4 and Lyt-2 that specifically deplete functional T cell subsets in mice. We demonstrate that such reagents can be used to control both graft-versus-host disease and marrow rejection in mouse models of bone marrow transplantation across one-haplotype or two-haplotype major histocompatibility differences. Such strategies to abrogate host resistance, by administration of anti-T-cell monoclonal antibodies to the recipient, may complement marrow T cell purging for human allogeneic bone marrow transplantation.