Increased iNOS-expressing macrophage in long-term surviving rat small-bowel grafts

BACKGROUND: Inducible nitric oxide synthase (iNOS) produces nitric oxide and modulates many biologic processes critical in the development of rejection; however, its role in chronic rejection (CR) in small-bowel transplantation (SBT) is largely unknown. METHODS: FK506 prevented acute rejection (AR); however, recipients eventually lost their bowel grafts to CR. Combined FK506 and rapamycin treatment prevented CR, thus leading to long-term graft survival. We investigated iNOS expression in our rat orthotopic SBT CR model. RESULTS: Histologically, mesentery vascular occlusion and fibrosis, which are hallmarks of CR, were apparent in bowel grafts in an FK506 single-treatment group. In contrast, patients with long-term surviving grafts receiving FK506 and rapamycin developed mild vascular occlusion and fibrosis. Unlike in AR, low iNOS expression, which is associated with decreased macrophage infiltration, was observed in CR grafts. However, iNOS expression and macrophage infiltration was higher in long-term-surviving grafts than CR grafts. Immunofluorescence staining revealed that the majority of macrophages expressed iNOS in long-term surviving grafts. COMMENTS: Sequential treatment combining FK506 and rapamycin prolonged survival of SBT animals with decreased vasculopathy and collagen deposition of the intestinal grafts. iNOS may play opposing roles in AR and CR in SBT.     

Immunologic benefits of longer graft in rat allogenic small bowel transplantation

BACKGROUND: The effect of graft length on rejection reaction in small bowel transplantation (SBT), which is poorly understood, is tested using rat allogenic SBT models with a short course of tacrolimus. MATERIALS AND METHODS: Inbred Brown Norway rats (major histocompatibility complex: RT1) and Lewis rats (RT1) were used as donors and recipients, respectively. The intestinal tract of the recipient was partially or totally replaced by segmental (15 cm) or whole (70 cm) donor intestine, using two different SBT models. With tacrolimus treatment (0.64 mg/kg per day, 0-13 postoperative days, intramuscularly), recipients' body weights and their survival were evaluated. To compare the extent of peripheral chimerism, donor passenger leukocytes were followed using flow cytometry with a donor-specific monoclonal antibody, OX-27. For the periodical histologic analysis, heterotopic SBT and protocol biopsies of the graft were also performed with short or long intestinal grafts. RESULTS: In a classical Monchik and Russell orthotopic SBT model, whole SBT recipients survived more than 60 days. However, all of the allogenic segmental SBT recipients died within 14 days without histologic sign of graft rejection. In the modified orthotopic SBT model using a cuff technique without systemic clamping, all recipients with segmental allograft survived longer than 29 days. However, recipients with whole graft tended to survive longer than those with segmental graft. The suffering period, lasting from the onset of rejection to death, was significantly shorter in the segmental group than in the whole group. Flow cytometric analysis showed that recipients with whole intestinal grafts had significantly higher ratio of donor passenger leukocytes in peripheral blood. Histologic studies of the protocol biopsies showed that the shorter graft tended to be more severely rejected than the longer graft. CONCLUSIONS: We have demonstrated experimentally that long intestinal grafts have immunologic advantage over short grafts.     

Effect of FTY720 and ex vivo graft irradiation in rat small bowel transplantation: apoptosis of crypt cells and lymphocytes

OBJECTIVE: We investigated the extent of apoptosis in crypt cells and Peyer's patches (PPs) during small bowel allograft rejection in rats to examine the effect of FTY720 and ex vivo graft irradiation during rejection. MATERIALS AND METHODS: Orthotopic small bowel transplantations (SBT) were performed from Brown Norway (BN) rats to Lewis (LEW) rats. Four groups of SBT animals were studied on days 3, 5, and 7 after operations: untreated allograft, allograft with FTY720, allograft with irradiation, and allograft with FTY720+irradiation. Cryostat sections were prepared from the grafts, including PPs. An in situ end-labeling (ISEL) technique was used to detect apoptotic cells. Indirect immunoperoxidase staining was also performed using monoclonal antibodies against rat Fas/FasL. RESULTS: The graft survival was prolonged in the FTY720-treated groups. In the FTY720-treated group, the number of ISEL-positive enterocytes was significantly down-regulated on days 3, 5, and 7 compared with the untreated allograft group. The number of ISEL-positive mononuclear cells was also significantly down-regulated compared with the untreated allograft group. The FTY720 the radiation and the FTY720+irradiation treated groups showed significantly down-regulated numbers of Fas/FasL-positive enterocytes on day 7 compared with the untreated allograft group. Fas/FasL-positive mononuclear cells were also significantly down-regulated in the allograft compared with the untreated allograft group. CONCLUSIONS: FTY720 and ex vivo graft irradiation prevented up-regulation of the number of apoptotic enterocytes, lymphocytes, and Fas/FasL-positive lymphocytes, and also prolonged small bowel allograft survival. Combination FTY720 and ex vivo graft irradiation did not affect graft survival and apoptotic cell expression compared with the FTY720 only group. These findings suggest that FTY720 may prevent both rejection-associated and sepsis-induced apoptosis during the late phase of small bowel graft rejection.     

Mucosal glutamine utilization after small-bowel transplantation: an electrophysiologic study.

A short course of FK 506 after small bowel transplantation averts rejection in the rat and achieves indefinite survival of the recipient whose nutritional status is dependent on the function of the intestinal graft. Ex vivo electrophysiologic studies using the Ussing Cell were conducted to delineate functional competence of the graft by evaluating mucosal ion transport and glutamine utilization. Orthotopic small-bowel transplantation was performed in Lewis (LEW) rats as recipients of either Brown-Norway (BN) allografts or LEW syngeneic grafts. Allograft recipients received FK 506 either as a short course (2 mg/kg on Day 0-4 after transplantation) or continuously (2 mg/kg Day 0-4, then 0.5 mg/kg weekly). Ileal mucosa was harvested from small bowel grafts 9 and 60 days after transplantation and mounted in the Ussing Cell containing Hanks' balanced salt solution with/without L-glutamine (20 mM). Transmembrane potential difference (PD), which represents mucosal active ion transport, and mucosal resistance, an index of membrane integrity, were recorded. Nine days after transplantation, mucosal PD was the same in the ileum from syngeneic grafts, allografts treated with FK 506 and normal LEW and BN rats, and the addition of glutamine increased PD equally in all groups. In comparison, PD was markedly decreased in allografts undergoing rejection, and the glutamine response was blunted. Sixty days after transplantation, mucosal PD was reduced in allografts treated with a short course of FK 506, but normal in allografts receiving continuous immunosuppression with FK 506 and in syngeneic grafts. A decrease of mucosal resistance was not a feature of rejection nor a sequel of limited FK 506 therapy. Our data indicate that allograft rejection results in a significant decrease in mucosal PD and a poor response to glutamine. Control of rejection by FK 506 preserves normal electrophysiologic responses of the allograft mucosa.     

Long-lasting donor passenger leukocytes after hepatic and intestinal transplantation in rats

BACKGROUND: Donor passenger leukocytes (DPLs) that migrate after organ transplantation stimulate the recipient immune system and normally cause rejection and graft vs. host reaction. However, DPLs also contribute to the unresponsiveness to the donor organ. The quantity and quality of these migrating cells are considered dependent on individual transplanted organs. We compared the DPLs of the liver, which might contain somatic stem cells, with those of intestinal grafts that have highly immunogenetic cells. To study DPLs over a long period, we used green fluorescent protein (GFP) transgenic (Tg) rats developed by us as donors. METHODS: We performed orthotopic liver transplantation (OLT) and small bowel transplantation (SBT) from GFP Tg rats to wild recipients. A short course of tacrolimus (0.64 mg/kg, intramuscularly) was used to prevent antigenicity of the GFP. The fate of the DPLs in the peripheral blood and the recipient bone marrow was monitored by flow cytometry. Using long-surviving recipients, the GFP(+) cells in the graft and various host immunologic organs were measured and characterized by immunohistochemical staining. RESULTS: In both groups, the numbers of the GFP(+) cells in the peripheral blood increased transiently and then gradually decreased to undetectable levels. While no GFP(+) cells were identified in the long-surviving-recipient bone marrow, there were a few GFP(+) cells in the graft liver, graft mesenteric lymph nodes and the recipient spleen. These cells showed major histocompatibility complex (MHC) class II antigen. There was no significant difference in the migration patterns of the GFP(+) cells in the OLT and SBT rats. CONCLUSIONS: In both the OLT and SBT groups, the DPLs migrated transiently in the recipient peripheral blood. A small numbers of MHC class II-positive DPLs were present at the graft site and in the host spleen, but not in the bone marrow. There were no significant differences in the migration patterns of the DPLs between the OLT and SBT rats over the long term.     

Hyperacute rejection in porcine liver transplantation. I. Clinical characteristics, histopathology, and disappearance of donor-specific lymphocytotoxic antibody from serum

Hyperacute rejection following orthotopic liver transplantation remains an extremely unusual occurrence. In this study, we examined a porcine model of liver transplantation in which recipient animals were sensitized prior to transplantation with three serial full-thickness skin grafts. Three experimental groups were studied. Group I recipients (n = 6) were specifically sensitized against their liver donors with biweekly skin grafts followed by hepatic grafting. Group II recipients (n = 6) underwent third-party skin graft sensitization prior to liver transplantation. Group III recipients (n = 6) underwent liver grafting without sensitization. Mixed lymphocyte cultures were done before each skin graft and prior to transplantation. Lymphocytotoxic antibody (LCTA) titers were measured before the first skin graft, at weekly intervals thereafter, intraoperatively, and daily postoperatively until death. Intraoperative and postmortem liver biopsies were obtained in all recipients. Five of six recipients in Group I died within 4 hr of hepatic revascularization. The remaining animal survived for four days. Mean survival time in group I was 0 +/- 0.7 days. In contrast, MST in groups II and III were 4.0 +/- 1.2 and 6.2 +/- 1.3 days, respectively. The MST in group I was significantly shorter than in groups II and III (P less than 0.026 and P less than 0.005, respectively). There was no significant difference in survival between groups II and III. MLC reactivity between recipients and skin donors increased progressively following each skin graft, reaching a peak just prior to liver transplantation. LCTA titers also increased following each skin graft, reaching peak levels immediately prior to hepatic grafting. Intraoperative LCTA titers decreased within 2 min of graft revascularization and were undetectable within 4 hr. In group III (unsensitized recipients), MLC reactivity was low and at no time was LCTA detectable. Histologic examination of the livers from group I recipients showed parenchymal hemorrhage, endophlebitis, and neutrophil infiltration. Histologic examination of postmortem liver biopsies from animals in groups II and III revealed acute cellular rejection. In conclusion, hyperacute rejection resulting in graft failure and recipient death can be consistently produced in a porcine model of hepatic transplantation by donor-specific sensitization of the recipient. It is postulated that high titers of donor-specific antibody are required to exceed the liver's capacity for antibody absorption and elimination and produce the clinical picture of hyperacute rejection.     

Partial donor-specific tolerance to delayed skin grafts after rejection of hematopoietic cell graft

BACKGROUND: Donor-specific tolerance (DST) is induced after allogeneic hematopoietic cell transplantation (HCT) and is a potential strategy for prolonging survival of solid organ grafts. DST may persist in recipients with transient mixed hematopoietic chimerism (MC) when solid organ transplantation and HCT are done concomitantly. METHODS: In a canine model of allogeneic HCT after nonmyeloablative conditioning, DST to skin grafts was evaluated in dog leukocyte antigen (DLA)-identical recipients with stable MC (n=11), or after rejection of the hematopoietic cell (HC) graft (n=19). RESULTS: There was significant improvement in the survival of DLA-identical HC donor-derived skin grafts in recipients with MC compared to normal recipients (n=7; P<0.0001). However, HC donor-derived skin grafts in four recipients with MC developed an inflammatory reaction without skin graft loss. This may represent partial DST. Survival of DLA-identical HC donor-derived skin grafts was also significantly prolonged compared to normal recipients even when skin grafting was delayed until after rejection of the HC graft (P=0.002). An inflammatory reaction developed in all nine of the surviving HC donor-derived skin grafts in this group, but there was no graft loss at last follow-up (median, 30 [range, 9-84] weeks). An increased time to rejection of the hematopoietic graft was associated with prolonged survival of the subsequent skin graft (P=0.02). CONCLUSION: In a model of stable MC, DST to skin grafts may be complete or partial. Partial DST can persist after HC graft rejection even if solid organ transplantation is delayed. Further investigations are required to understand the mechanisms responsible for DST after allogeneic HCT.     

Changes in the composition of serum bile acid as a predictor of small bowel allograft rejection in rats

Composition of bile acid was studied as a noninvasive rejection marker after small bowel transplantation (SBT). Orthotopic SBT were performed in rats, and they were divided into four groups: group 1, sham-operated rats; group 2, recipients with isografts; group 3, recipients with allografts treated with FK506; and group 4, recipients with untreated allografts. On postoperative days (POD) 5 and 7, the graft histology, intraluminal bacterial overgrowth, individual bile acids concentration of the recipient serum and bile were examined. On POD 5, early histological findings of acute rejection were observed in group 4, and the ratio of secondary bile acids of this group were significantly higher than the other groups. The bile acid changes were enhanced by bacterial overgrowth on POD 7. The ratio of secondary bile acids changed in relation to acute rejection after SBT, suggesting that they can be useful for early diagnosis of acute SBT allograft rejection.     

Liver allografts are toleragenic in rats conditioned with posttransplant total lymphoid irradiation

BACKGROUND: Posttransplant total lymphoid irradiation (TLI) treatment has been applied to tolerance induction protocols in heart and kidney transplantation models. METHODS: We examined the efficacy and mechanism of posttransplant TLI treatment in the induction and maintenance of tolerance in a rat orthotopic liver transplantation model. RESULTS: Posttransplant TLI prolonged ACI (RT1(a)) liver allograft survival in Lewis (RT1(b)) hosts, with 50% long-term engraftment without immunosuppression and without evidence of chronic rejection. Injection of donor-type liver mononuclear cells (LMCs) facilitated the prolongation of graft survival, with more than 70% of grafts in LMC recipients surviving more than 100 days without chronic rejection. Recipients with long-term liver allograft survival accepted ACI but not PVG skin grafts. In TLI-conditioned recipients with accepted grafts, apoptosis occurred predominantly in graft-infiltrating leukocytes. In contrast, there were few apoptotic leukocytes in rejecting grafts. Recipients with long-term graft acceptance (>100 days of survival) demonstrated evidence of immune deviation; mixed lymphocyte reaction to ACI stimulator cells was vigorous, but secretion of interferon-gamma and interleukin-2 was reduced. In tolerant recipients, the number of Foxp3(+) CD25(+) CD4(+) regulatory T cells was increased in the liver allograft as well as in the peripheral blood. CONCLUSION: We conclude that posttransplant TLI induces tolerance to liver allografts via a mechanism involving apoptotic cell-deletion and immunoregulation.     

Effect of FTY720 in rat small bowel transplantation: apoptosis of crypt cells and lymphocytes in gut-associated lymphoid tissues

AIM: We investigated the extent of apoptosis in crypt cells and Peyer's patches (PPs) during small bowel allograft rejection in rats to examine the effect of FTY720 during rejection. METHODS: Orthotopic small bowel transplantations (SBTs) were performed from BN to LEW rats. Isografted animals served as controls. Three groups of SBT animals were studied on days 3, 5, and 7 after operation: isograft, untreated allograft, allograft with FTY720. FTY720 was orally administered by gavage (1 mg/kg/d) to allograft recipients on 7 consecutive days. Cryostat sections were prepared from grafts, including PPs. An in situ end-labeling (ISEL) technique was used to detect apoptotic cells. Indirect immunoperoxidase staining was also performed using monoclonal antibodies against rat Fas/Fas-L. RESULTS: Graft survival was prolonged in the FTY720-treated group. The number of ISEL-positive enterocytes in the allografts increased significantly on days 3, 5, and 7 compared with the isograft group. In the FTY720-treated group, the number of ISEL-positive enterocytes in the allografts was down-regulated significantly on days 3, 5, and 7 compared with untreated allograft group. In the PPs, the number of ISEL-positive mononuclear cells increased significantly in the allografts compared with the isograft group. In the FTY720-treated groups, the number of ISEL-positive mononuclear cells were down-regulated significantly in the allografts compared with the untreated allograft group. The number of Fas/FasL-positive enterocytes were increased significantly in allografts compared with isograft group. In FTY720-treated groups, the number of Fas/FasL-positive enterocytes were down-regulated significantly on day 7 compared with the untreated allograft group. In the PPs, Fas/FasL-positive mononuclear cells also increased significantly on day 7 in the allografts compared with isografts. In the FTY720-treated groups, Fas/FasL-positive mononuclear cells were down-regulated significantly in the allografts compared with the untreated allograft group. CONCLUSIONS: The number of apoptotic enterocytes, lymphocytes, and Fas/FasL-positive lymphocytes increased during small bowel graft rejection. FTY720 prevented up-regulation of the number of apoptotic enterocytes, lymphocytes, and Fas/FasL-positive lymphocytes while also prolonging small bowel allograft survival.     

Real-time monitoring for detecting rejection using strain gauge force transducers in porcine small bowel transplantation

PURPOSE: The clinical results of small bowel transplantation (SBT) have not been satisfactory mainly because of the immunological barrier. It is important to detect the presence of and to perform adequate treatment of rejection as early as possible to improve graft survival. Therefore, we have established a pig model to monitor graft motility as a means to detect rejection in real time. METHODS: Orthotropic SBT was performed in 25 pigs using FK-506 (0.05 to 0.1 mg/kg/d) immunosuppression. The interdigestive motor patterns were evaluated using strain gauge force transducers (SG). Seven pigs without SBT were treated as controls (C). Animals that displayed migrating motor complex (MMC) activity as evidenced by duration, amplitude, and interval in the graft were alive more than 10 days with adequate oral feeding: the functional graft (FG) group. In contrast the rejection (R) group did not show these activities on data recorded within 10 days before death due to rejection. RESULTS: The FG group showed MMC propagated throughout the graft with all parameters almost the same as the control group except for the duration. In contrast, all parameters in the group R were significantly lower than those in group FG, suggesting that group R motility was obviously impaired by rejection. CONCLUSIONS: The SG method may afford real-time monitoring of transplanted bowel motility that could be useful to detect rejection after SBT.     

Effect of cyclosporin therapy in controlling the rejection of ileal versus jejunal allografts*

Abstract. Experimental evidence suggests that jejunal allografts are rejected as rapidly as are ileal grafts, despite their lesser content of lymphoid tissue as an immunologic stimulus. However, it may be possible to postpone the rejection of jejunal grafts more readily than that of ileal grafts by means of immunosuppressive therapy with cyclosporin (CyA). To test this, we used the rat model (BN-LEW) of orthotopic small-bowel transplantation. The proximal third of the small-bowel with one-third of the mesenteric lymph nodes (n= 20), or the distal ileal third with all of the mesenteric lymph nodes (n= 22), or the entire small-bowel (n= 23) was interposed after resection of an equivalent type and length of recipient bowel. CyA (15 mg/kg) was given to all of these rats for 5 days. Three additional control groups were not given CyA. The difference in graft/recipient survival among the groups receiving CyA and among those not on CyA therapy was not statistically significant. Antidonor hemagglutinin titers, the mixed lymphocyte culture (MLC) assay, and histologic examination of the allograft failed to show a mitigated rejection reaction for the recipients of jejunal grafts. The data show that short-term treatment with CyA prolongs graft survival. Equal doses of CyA, however, did not lead to prolonged survival of jejunal grafts or alter the course of rejection in comparison with that for ileal or whole-bowel transplants.     

移植物局部转染CTLA4Ig基因对大鼠小肠移植排斥反应的预防作用

目的探讨CTLA4Ig基因在移植小肠局部转染表达及表达产物对排斥反应的预防作用。方法大鼠小肠移植前,经肠系膜上动脉给供肠灌注脂质体包裹的CTLA4IgcDNA重组质粒,术后应用组织免疫学及逆转录聚合酶链反应(RTPCR)检测移植小肠中CTLA4Ig转基因产物的表达,并行组织病理学检查,同时设立无CTLA4Ig基因转染的对照组。结果对照组(n=8)的移植小肠在术后7～14d全部坏死;实验组(n=18)7只受鼠的移植小肠于术后56～90d坏死,11只受鼠的移植小肠于术后90d时仍存活良好。对照组移植物组织切片见单核细胞广泛浸润,肠壁肌层及黏膜出血坏死,绒毛及隐窝结构消失;实验组存活超过90d者组织切片仅见少量单核细胞浸润,黏膜轻度增厚,但无明显的肠绒毛缩短及隐窝细胞减少等改变。组织免疫学及RTPCR结果显示,在移植后28d内移植小肠中有CTLA4Ig转基因产物的表达,但第56d及90d则检测不到其表达。结论经肠系膜上动脉体外灌注脂质体包裹的CTLA4IgcDNA重组质粒可有效转染移植小肠,CTLA4Ig基因在移植小肠局部转染对术后的排斥反应具有预防作用。     

Tolerance induced by bone marrow chimerism prevents transplant vascular sclerosis in a rat model of small bowel transplant chronic rejection

BACKGROUND: The major impediment to success in solid organ transplantation is chronic rejection (CR). The characteristic lesion of CR is transplant vascular sclerosis (TVS). Although the mechanism of TVS is thought to have an immunologic basis, in humans immunosuppression does not prevent or reverse it. One possible therapy to prevent TVS is induction of donor-specific tolerance. Bone marrow chimerism has been successful in inducing tolerance in acute and chronic rejection heart and kidney transplant models. The highly immunogenic small bowel (SB) allograft provides a rigorous test of the efficacy of this tolerance regimen. We examined whether induction of tolerance by bone marrow chimerism could prevent TVS in a model of Fisher 344 (F344) to Lewis (LEW) rat SB transplantation. METHODS: Bone marrow chimeras (BMC) were created by transplantation of T-cell-depleted F344 bone marrow into irradiated LEW rats. Chimerism was assessed by flow cytometric method. F344 SB, heterotopically transplanted into the chimeras, was clinically and histologically assessed for CR. F344 SB grafts, transplanted into cyclosporine-A-treated LEW recipients, served as control grafts for CR. RESULTS: Cyclosporine-A-treated LEW rats chronically rejected F344 SB grafts. By contrast, the BMC group demonstrated tolerance and had long-term SB graft survival (>120 days) without TVS. The BMC demonstrated immunocompetence by prompt rejection of third party ACI (RT1av1) SB allografts. CONCLUSIONS: Bone marrow chimerism prevents chronic graft failure secondary to TVS in a model of chronic SB rejection. TVS fails to develop when tolerance is established, suggesting that the mechanisms involved in TVS are, in part, immunologically mediated.     

Structure and function of orthotopic small bowel allografts in rats treated with cyclosporine

Previous studies of small bowel transplantation using a variety of animal models and immunosuppressive regimens have failed to demonstrate consistently prolonged survival of bowel allografts capable of maintaining a normal nutritional state. In the present study, total orthotopic small bowel transplantation was performed in inbred rat strains to determine the structure and function of intestinal allografts using cyclosporine for immunosuppression. Without cyclosporine, Lewis-Brown Norway and Brown Norway allografts were quickly rejected by Lewis recipients, resulting in host death. A 15 mg/kg dose of cyclosporine given intramuscularly immediately after operation and for 6 successive days thereafter achieved prolonged but not uniformly indefinite animal and graft survival with clinical courses and pathologic findings consistent with chronic rejection. With continuation of cyclosporine every other day until day 28, all Lewis recipients of Brown Norway allografts were alive and well 8 months after transplantation. Weight gain, maltose absorption, and multiple nutritional indices in these animals were not significantly different from those of either age-matched normal Lewis rats or recipients of Lewis isografts. Full-thickness biopsy specimens of these allografts showed no evidence of graft rejection. These results demonstrate that indefinite survival of intestinal allografts with preservation of their structure and function sufficient to allow normal growth and weight gain can be achieved with cyclosporine therapy. This success in the rat model of orthotopic small bowel transplantation suggests that clinical small-bowel transplantation may become possible using cyclosporine.     

Long‐term small bowel allograft function induced by short‐term FK 506 application is associated with split tolerance

Abstract Functional long‐term allograft survival after experimental small bowel transplantation (SBT) is limited by chronic rejection. Initial application of high‐dose FK 506 has been shown to induce stable long‐term graft function. In order to examine whether this long‐term function is associated with donor‐specific tolerance, we analyzed the functional status of recipient T cells in vivo and in vitro. One‐step orthotopic SBT was performed in the allogeneic Brown Norway (BN)‐to‐Lewis rat strain combination. FK 506 was given daily at a dose of 2 mg/kg from days 0‐5 in the rejection model and from days 0‐9 in the long‐term functional model. Mean survival time in the rejection model was 98 ± 2.8 days. Histological examination of these small bowel allografts disclosed signs of chronic rejection. In contrast, all animals of the long‐term functional model survived long term (> 250 days) without clinical signs of chronic rejection. The latter model, furthermore, produced evidence of donor‐specific tolerance. Whereas heterotopic Dark Agouti (DA) hearts were rejected regularly within 7 days, BN hearts survived indefinitely (> 70 days). In vitro, mixed leukocyte reactivity of CD4 + T cells was similarly strong against donor (BN) antigens as against third‐party (DA) antigens. The split tolerance revealed by our in vivo and in vitro results enabled acceptance of both the small bowel allograft without signs of chronic rejection and of donor‐specific heart allografts.     

Recipient growth and nutritional status following transplantation of segmental small-bowel allografts

Concerning small-bowel transplantation in children, the question arises whether a segmental small-bowel graft from an adult donor would permit normal growth of the young recipient. Orthotopic small-bowel transplantation was performed in 4- to 6-week-old Lewis rats weighing 100-135 g. The entire small bowel of the recipient was replaced with an intestinal allograft consisting of the entire small bowel (N = 6), the jejunum (N = 6), or the ileum (N = 6) from adult Brown Norway rats. Immunosuppression with cyclosporine (15 mg/kg im) on alternate days for 4 weeks achieved graft acceptance of indefinite duration. Six and twelve months after transplantation, all recipients demonstrated normal global nutritional parameters (hematocrit, serum albumin) and gained weight at a rate comparable to that for age-matched controls. Nutritional deficiencies did not become apparent clinically. By 10 to 12 months, the levels of fat-soluble vitamins (A and E) were reduced significantly in recipients of segmental grafts. Vitamin B12 levels were also reduced but not significantly. Fecal fat was significantly elevated in all rats with grafts (3.2 +/- 1.0 to 4.8 +/- 0.9 g fat/100 g stool; controls, 1.8 +/- 0.4), but the increase was most pronounced in those with jejunal grafts (4.7 +/- 0.9). This was paralleled by a reduction in serum triglyceride levels in all transplanted rats, a reduction which reverted to normal by 10 to 12 months for rats with entire small-bowel grafts but not for those with segmental grafts. Graft biopsy demonstrated normal intestinal architecture with villus hyperplasia of segmental grafts.(ABSTRACT TRUNCATED AT 250 WORDS)     

The effects of cyclosporine on varying segments of small-bowel grafts in the rat

The relationship between the cyclosporine A (CSA) dose and rejection of varying lengths of small-bowel grafts was studied in a rat heterotopic microsurgical small-bowel transplantation model involving a haploidentical strain combination. When Lewis X Brown Norway F1 hybrid (LBN) small-bowel grafts were transplanted into Lewis (LEW) rats without CSA, all grafts in the proximal 10 cm, the proximal 40 cm, and the entire (approximately 80 cm) small bowel were rejected on days (mean +/- SEM) 6.6 +/- 0.2 (n = 11), 7.0 +/- 0.4 (n = 6), and 7.8 +/- 0.7 (n = 6), respectively. A 10-day course (days 0-9) of CSA 2 mg/kg significantly (p less than 0.05) prolonged the survival of the proximal 10 cm, the proximal 40 cm, and the entire small bowel allografts to days 18.8 +/- 1.7 (n = 5), 16.5 +2- 1.3 (n = 6), and 13.5 +/- 1.0 (n = 4), respectively. Similarly, the CSA 5 mg/kg regimen significantly (p less than 0.05) delayed the rejection of the 10 cm, the 40 cm, and the 80 cm small-bowel grafts to days 50.2 +/- 7.2 (n = 6), 47.7 +/- 2.6 (n = 3), and 40.3 +/- 5.8 (n = 3), respectively. However, 6 of 12 rats treated with CSA 5 mg/kg died of pneumonia, and these animals were all in groups with the 40 cm and 80 cm grafts. When these animals were included in calculations of rejection-free survival, the averages for the 40 and 80 cm groups treated with CSA 5 mg/kg were 34.2 +/- 6.4 and 28.7 +/- 6.1 days, respectively. CSA suppressed rejection of small-bowel allografts in a dose-related fashion. More important, significantly (p less than 0.05) lower doses of CSA were necessary for rats that received shorter intestinal grafts. In fact, the relationship between rejection and CSA dose in the 10 cm grafts was characterized by the formula: day of rejection = 9.3 [CSA dose]1.03. We conclude that the ideal small intestinal graft should be the smallest possible segment that maintains adequate nutrition and CSA doses should be matched for segment lengths.     

肠移植早期黏膜地址素细胞黏附分子在大鼠移植小肠及其肠系膜淋巴结的表达

目的 探讨黏膜地址素细胞黏附分子（MAdCAM-1）在大鼠小肠移植早期移植肠及其肠系膜淋巴结中的表达及意义。方法 选用近交系F344／N和BN大鼠建立全小肠异位移植模型后分3组：第1组，非手术对照组（F344／N）；第2组，同基因移植组（F344／N→F344／N）；第3组，异基因移植组（BN→F344/N）。术后1、3、5、7d取各组移植肠及其肠系膜淋巴结检测MAdCAM-1表达的分布及变化，同期进行移植肠组织病理学检查。结果 同基因移植组各检测时点的肠黏膜组织表现与正常小肠的组织学特征基本相同；异基因移植组肠黏膜组织表现符合轻-中-重度排斥反应的渐进过程，2周后移植肠绒毛变的低平，散在黏膜上皮脱落，移植肠相关肠系膜淋巴结萎缩明显。MAdCAM-1在急性排斥反应期，高表达于移植肠固有层及其肠系膜淋巴结，特别是高表达于肠黏膜固有层中的扁平血管内皮细胞表面。同基因移植组术后MAdCAM-1的表达在1—7d均无明显量的变化；而异基因移植组MAdCAM-1在移植肠中的表达呈上升趋势，而在其肠系膜淋巴结中的表达呈下降趋势。结论 MAdCAM-1与小肠移植急性排斥反应的进展关系密切。