The immunomodulatory effect of cryopreservation in rat tracheal allotransplantation.

BACKGROUND: Cryopreservation is one solution to the problem of donor organ deficit. To investigate the effect of cryopreservation on tracheal allografts, we performed 2 experiments in rats. METHODS: In Experiment 1, we assessed second-set graft rejection. Two weeks after primary heterotopic transplantation (Group 1, fresh isografts; Group 2, fresh allografts from Lewis rats; and Group 3, cryopreserved allografts from Lewis rats; n = 5, respectively), each animal underwent secondary heterotopic grafting with isografts and allografts from Lewis and Wistar Furth rats (n = 5, respectively). Four weeks after the secondary transplantation, all grafts were retrieved for histologic analysis. In Experiment 2, we assessed the long-term results of allograft cryopreservation, without immunosuppression therapy. Six months after transplantation of fresh (Group 4) and cryopreserved (Group 5) allografts, the tracheal segments (each group, n = 5) were histologically evaluated. RESULTS: In Experiment 1, only the secondary allografts from Lewis rats in Group 2 did not maintain lumen structure and often showed dislocated or destroyed cartilage. Second-set graft rejection was specifically recognized in Group 2, but not in Group 1 or 3. In Experiment 2, the cryopreserved allografts appeared almost normal and lumen rigidity was preserved 6 months after transplantation. These allografts were superior to the fresh allografts in patency and in cartilage dislocation and mononuclear cell infiltration scores, but not in the viable chondrocyte ratio. CONCLUSIONS: We conclude that cryopreservation may produce successful long-term results because of its immunomodulatory effect on tracheal allografts.     

Molecular mechanism of contractile dysfunction in cardiac allograft rejection.

Alterations in the beta-adrenergic receptor adenylyl cyclase pathway are well known in heart failure. To determine if an alteration in this pathway occurs during the reversible phase of cardiac allograft rejection, we used a rat heterotopic heart transplant model. Lewis rats received either isografts or Lewis Brown Norway allografts. Cardiac grafts and native hearts were explanted 4, 5, or 6 days later. Receptor-mediated modulation of adenylyl cyclase activity was investigated using isoproterenol, forskolin, and the muscarinic and adenosine receptor agonists carbachol and R-N6-(C2-phenyl-isopropyl)-adenosine (R-PIA), respectively. Allografts demonstrated evidence of histological rejection and a significantly impaired response to forskolin and isoproterenol on all days: [table: see text] (% increase in cAMP in response to forskolin or isoproterenol +/- standard error. All results P less than 0.03 except Day 4 forskolin and Day 5 isoproterenol.) No significant difference was noted between isografts and allografts stimulated with carbachol and R-PIA. These data suggest that a primary alteration in adenylyl cyclase activity may be a component of the molecular basis of reversible contractile dysfunction in cardiac allograft rejection.     

Gene expression profile during acute rejection in rat-to-mouse concordant cardiac xenograft by means of DNA microarray

Using a rat-to-mouse concordant cardiac transplantation model and DNA microarrays, we studied the gene expression profiles during acute rejection. We used inbred BALB/c and C3H/He mice and Lewis rats for our study, in which heterotopic cardiac transplantations were performed. Total RNA was isolated from xenografts (Lewis to C3H), allografts (BALB/c to C3H), rat isografts (Lewis to Lewis) and mouse isografts (C3H to C3H) on day 5 following transplantation. We screened for gene expression profiles in the xenografts, allografts, and mouse isografts by means of DNA microarrays. With a murine array, we determined that many IFN-gamma inducible genes were profoundly expressed in both the allografts and xenografts relative to the isografts. Mac-1 was specifically induced in the xenografts relative to the allografts. Using a rat array, we observed that the cardionatrin and atrial natriuretic factors were most profoundly expressed in the xenografts in comparison with the rat isografts. In addition to known genes, many expressed sequence tags were induced in the xenografts. We identified a group of genes, including Mac-1 induced specifically in xenografts, as well as many new genes upregulated in xenografts.     

Modulation of catecholamine responsiveness and beta-adrenergic receptor/adenylyl cyclase pathway during cardiac allograft rejection1 2

BACKGROUND: This study investigated the changes of catecholamine responsiveness and beta-adrenergic receptor/adenylyl cyclase pathway during acute cardiac transplant rejection. METHODS: Isogeneic Lewis to Lewis and allogeneic Dark Agouti (DA) to Lewis rat cardiac transplants were studied 3 and 5 days after heterotopic intraabdominal transplantation (n=6/group). Myocardial blood flow (MBF), left ventricular systolic pressure (LVSP), maximum pressure development (+dP/dt), and end-diastolic pressure (LVEDP) were measured using an intraventricular balloon. Contractile response to dobutamine (5 microg/kg/min) was also assessed. In separate groups beta-adrenergic receptor density and adenylyl cyclase activity were measured in the grafts, in the recipients' native hearts and in native hearts of sham-operated controls. RESULTS: During mild to moderate rejection cardiac function indices remained unchanged, although MBF and contractile response to dobutamine decreased significantly (P<0.05) in the allogeneic group. The beta-adrenergic receptor density was significantly (P<0.05) increased in both isografts and allografts and in the native hearts of allografted recipients in comparison to native hearts of controls. Adenylyl cyclase activity showed a significant decrease (P<0.05) only in allografts. During severe rejection, LVSP and +dP/dt decreased and LVEDP increased in allografts in comparison to isografts (P<0.05). This was accompanied by a significant decrease in MBF, contractile response to dobutamine, beta-adrenergic receptor density, and adenylyl cyclase activity (P<0.05). CONCLUSIONS: Both microcirculatory disturbances and primary alteration in adenylyl cyclase activity may contribute to decreased contractile reserve in mild to moderate cardiac allograft rejection, whereas beta-adrenergic receptor density seems to be also influenced by cardiac denervation. Severe rejection leads to systolic and diastolic heart failure with complex dysregulation of the beta-adrenergic receptor/adenylyl cyclase pathway and impaired microcirculation.     

31P nuclear magnetic resonance of rat pancreatic grafts

This study investigates whether phosphate metabolite concentrations and intracellular pH alter in early acute rejection of rat pancreatic allografts. In vitro biochemical assays, in vitro 31P nuclear magnetic resonance spectroscopy, and in vivo 31P NMR spectroscopy of the grafts were compared. Duct-ligated, vascularized rat pancreatic isografts and allografts were transplanted onto the infrarenal aorta of the recipients with inferior vena cava venous drainage. In order to obtain reproducible acute rejection, allografting was performed across a major histocompatibility barrier. For the in vitro experiments freeze-clamped graft extracts were prepared and analyzed for adenosine triphosphate concentration by fluorimetry, then placed in an 8.5 Tesla vertical bore magnet. 31P NMR spectra were recorded using a Bruker AM 360 spectrometer operating at 145.7 MHz for 31P. Spectra were acquired from nontransplanted controls; 3-day, 5-day, and 1-month posttransplant isografts, and 3-day and 5-day posttransplant allografts. All grafts examined were functioning satisfactorily. The ATP content of the extracts was significantly lower in the 3- and 5-day allografts than the respective isografts. Invasive in vivo 31P NMR spectra were recorded using surface coils adjacent to the grafts from functioning 5-day posttransplant isografts and allografts (i.e., 3 days prior to an expected elevation in blood sugar from acute rejection in the allografts). The ATP/inorganic phosphate ratios and pH from the in vivo spectra were significantly lower in the allografts than in the isografts. It is concluded that changes in intracellular metabolism occur early in the process of acute rejection and that 31P NMR spectroscopy may provide a means of diagnosing this before current methods.     

Evidence of mitochondrial impairment during cardiac allograft rejection

NADH laser fluorimetry and mitochondrial oxigraphy were used to study myocardial oxidative energy metabolism during cardiac allograft rejection. Heterotopic cardiac transplantation was performed on Lewis rats; allografts (with Fischer rat donors) were compared with isografts (with Lewis rat donors). In vivo and in vitro assays were performed six days after transplantation. Myocardial NADH fluorescence was recorded in vivo from grafted hearts, at baseline; during brief, complete ischemia; and during reperfusion. Oxygen consumption of mitochondria isolated from both native and grafted hearts was determined. Neither baseline levels nor maximum ischemic levels of NADH fluorescence (F0 = k[NADH]) were found to be significantly different between allografts (0.45 +/- 0.05 to 0.87 +/- 0.10) and isografts (0.45 +/- 0.04 to 1.11 +/- 0.05). During recovery, the rate of fluorescence decrease was significantly lower in allografts than in isografts (0.024 +/- 0.001 vs. 0.038 +/- 0.002 delta F0.s-1, P less than 10(-3], indicating a lower rate of NADH reoxidation. In the presence of malate and glutamate substrates, mitochondrial O2 consumption was significantly lower in allografts than in isografts (30 +/- 9 vs. 100 +/- 15 nanoatoms O2. min-1.mg prot-1, P less than 10(-2]. These results indicate that mitochondrial oxidative metabolism was impaired during the rejection process. Such energy production disturbances may contribute to the dysfunction of rejecting hearts.     

Failure of cyclosporin a to rescue peripheral nerve allografts in acute rejection

Prevention and control of graft rejection remain essential in the investigation of peripheral nerve allotransplantation. Although use of cyclosporin A (CsA) has been shown to suppress successfully the rejection of nerve allografts, limited information exists concerning use of this drug to arrest rejection in progress, and thereby effect salvage of these grafts. The aim of this study was to determine the efficacy of CsA in the treatment of ongoing acute rejection of peripheral nerve allografts. Buffalo rats received posterior tibial nerve grafts from either Lewis or Buffalo donor animals and were divided into five groups: group 1 received isografts and no CsA treatment (n = 8), group 2 received allografts with continuous CsA therapy (n = 10), group 3 received allografts with no treatment (n = 7), group 4 received allografts with initiation of CsA therapy delayed until 3 weeks after the procedure (n = 11), and group 5 received allografts with an interrupted course of CsA (n = 15). All grafts were harvested at 10 weeks. Histomorphometric analysis demonstrated comparable nerve regeneration in groups 1 and 2 and good regeneration in group 3 animals, despite cellular infiltrate suggestive of rejection. At 3 weeks after surgery, group 4 animals showed early rejection and significantly less neuroregeneration than positive controls at 10 weeks after delayed initiation of CsA therapy. Finally, group 5 animals showed early regeneration at 3 weeks but significantly lesser regeneration by 10 weeks after interruption of therapy. In this experimental protocol, CsA was ineffective in rescuing histologically proven rejection in progress.     

Tolerance induction permits the development of graft-versus-host disease: donor-mediated attack following small bowel transplantation in mixed chimeras.

The induction of tolerance to organ allografts would eliminate acute and chronic rejection as well as the need for nonspecific immunosuppression. We have shown that tolerance induced through the creation of mixed allogeneic bone marrow chimeras allows for the long-term engraftment of cardiac and small bowel allografts across strong multiple major histocompatibility barriers. The possibility that tolerance might render the host susceptible to graft-versus-host disease (GVHD) has not been investigated in this or other models of tolerance. To test this possibility chimeras were created by transplantation of T-cell depleted ACI and Lewis bone marrow into lethally irradiated Lewis rats. Chimerism was determined post bone marrow transplant (BMTx) by flow cytometry of lymphocytes from reconstituted animals. ACI/Lew chimeras (ALC), Lewis/ACI F1 (LACF1), and Lewis (LEW) rats all received heterotopic ACI vascularized small bowel grafts. A second group of chimeras received small bowel grafts from ACI rats pretreated with low dose irradiation to eliminate T-cells from the graft. LEW-->LEW small bowel isografts were also performed. Animals were examined for evidence of GVHD by clinical signs and histologic examination of biopsied tissues. GVHD was quantified using the popliteal lymph node enlargement assay. All LACF1 rats developed severe lethal GVHD following ACI small bowel transplant. Bone marrow chimeras, ALC (n = 6), developed fatal GVHD in a similar fashion after receiving a small bowel transplant. LEW-->LEW isografts and chimeras receiving bowel from irradiated ACI rats survived long term without GVHD while ACI-->LEW allogeneic transplants all underwent acute rejection. GVHD or its absence was confirmed histologically. Popliteal lymph node enlargement indices reflected the presence of GVHD in the chimeras (1.87) and LACF1 (5.4) receiving allografts, but not in isografts or chimeras receiving irradiated allogeneic transplants. Analysis of cytokines in the tongues of rats undergoing GVHD showed elaboration of Th1 type proinflammatory cytokines which was not seen in isografted rats or rats receiving preirradiated small bowel. These results demonstrate that tolerance induction through mixed chimerism results in susceptibility to small bowel induced GVHD. Preirradiating the donor bowel prior to SBTx can prevent GVHD.     

Transplantation of the entire small bowel in inbred rats using cyclosporine

Inbred strains of rats were used to analyze unidirectional host-versus-graft disease (transplant rejection) without graft-versus-host disease in small intestinal transplants and the immunosuppressive properties of cyclosporine (CsA). Forty-six Lewis rats received heterotopic transplants of the entire small bowel in four groups: Lewis-to-Lewis isografts, without CsA; Lewis-to-Lewis isografts, with CsA (15 mg/kg/day); (Lewis X ACI)F1-to-Lewis allografts, without CsA; (Lewis X ACI)F1-to-Lewis allografts, with CsA. Small bowel rejection was associated with gross morphological changes that preceded all other findings. A histologic scoring system assessed the degree of transplant rejection. A characteristic transient weight loss was seen in animals rejecting their bowels. Glucose absorption was impaired and polyethylene glycol absorption increased during rejection. Cyclosporine inhibited all of these changes in allografted rats. It is concluded that daily administration of cyclosporine is effective in preventing the morphologic and functional changes of acute transplant rejection in intestinal allografts and does not change these parameters in transplants that are not rejecting.     

Intragraft delivery of 16, 16-dimethyl PGE2 induces donor-specific tolerance in rat cardiac allograft recipients

The stable prostaglandin E2 analogue, 16,16-dimethyl PGE2 (di-M-PGE2) was continuously infused by osmotic pump directly into rat heterotopic cardiac allografts. Intragraft delivery of 20 micrograms/kg/day di-M-PGE2 for 2 weeks completely prevented graft rejection for more than 150 days (n = 10), while untreated Buffalo recipients rejected Lewis cardiac allografts within 8 days after transplantation (mean survival time = 7.4 +/- 0.5 days, n = 5). When given for only 1 week, 20 micrograms/kg/day had a partial effect, since 60% of recipients accepted grafts long-term and 40% experienced rejection by day 14 (n = 5). In contrast, systemic intravenous administration of 20 micrograms/kg/day di-M-PGE2 for 2 weeks could not prolong graft survival (MST = 7.0 +/- 0.0 days, n = 3), and the higher dose of 200 micrograms/kg/day resulted in death by day 2 (n = 5). Long-term BUF recipients of LEW cardiac allografts accepted LEW donor strain skin grafts for more than 35 days while rejecting third-party Wistar Furth skin grafts in a normal fashion (MST = 7.3 +/- 0.5 days, n = 3), indicating the induction of donor-specific tolerance. Long-surviving LEW cardiac allografts retransplanted into naive BUF recipients were rejected within 7 days (MST = 6.7 +/- 0.5 days, n = 3), indicating no change in graft immunogenicity. Therefore, a 14-day infusion of di-M-PGE2 directly into a strongly MHC-mismatched cardiac allograft uniformly has resulted in long-term engraftment and the development of recipient donor-specific tolerance.     

Changes in myocardial beta-adrenergic receptors during acute rejection of heterotopically transplanted rat hearts.

To evaluate changes of the myocardial beta-adrenergic receptors in acute cardiac graft rejection, the density and binding affinity value of the myocardial beta-adrenergic receptors in heterotopically transplanted rat isografts and allografts were analyzed. Hearts from Fisher rat donors were transplanted either to the Fisher rats (isografts) or to Lewis rats (allografts). Histologic examination of the allografts showed mild to moderate rejection on the seventh and fourteenth days and showed severe rejection on the twenty-first day after transplantation. The density values in the allografts and isografts similarly increased significantly (p < 0.05) above the normal level on the seventh and fourteenth days after transplantation. The density in allografts on the twenty-first day decreased significantly (p < 0.05) below the normal level, while that in isografts remained at the normal level. In contrast, the binding affinity value of myocardial beta-adrenergic receptors in both isografts and allografts did not change after transplantation. These results demonstrated that myocardial beta-adrenergic receptors presented upregulation in mild to moderate rejection, whereas these receptors presented downregulation in severe rejection. The data suggested that downregulation of myocardial beta-adrenergic receptors plays a major role in decreased cardiac contractility during severe rejection, but not during mild and moderate rejection.     

Cryopreservation prevents arterial allograft dilation

Historically, immune-mediated degradation and subsequent aneurysm formation have limited the usefulness of cryopreserved arterial allografts. This study tested the hypothesis that modern cryopreserved arterial allografts are protected from immune-mediated dilation. Abdominal aortas were harvested from anesthetized rats (Lewis and Brown-Norway) for immediate implantation or cryopreservation. Subsequently, Lewis rats underwent infrarenal aortic replacement with either an acutely harvested or a cryopreserved graft. There were four experimental groups: (1) acutely harvested isografts (Iso; n = 6), (2) cryopreserved isografts (C-Iso; n = 6), (3) cryopreserved allografts (C-Allo; n = 6), and (4) acutely harvested allografts (Allo; n = 6). All grafts were explanted at 8 weeks. A video camera and edge detection software were used to measure systolic and diastolic in vivo graft diameter (d). Measurement of arterial blood pressure (p) allowed calculation of compliance (Dd/Dp). Tail-cuff plethysmography was used to assess graft patency at 1 week. Graft diameter and blood pressure measurements were repeated at harvest. All harvested grafts were examined histologically. Our results showed that cryopreservation prevented immune-mediated dilation in arterial allografts in our 8-week rat implant model. Furthermore, the compliance of the cryopreserved grafts and was similar to that of controls. Further investigation is needed to delineate the exact mechanism of these potential cliniclly significant findings.     

Asynchronus rejection of intrathoracic heart-lung transplantation rats

We have reported intrathoracic heart-lung transplantation in rats could be made easily by using Internal Shunt Method as described elsewhere. In this study, we examined the rejection of intrathoracic heart-lung allografts in this model to determine whether acute pulmonary rejection precedes cardiac rejection following heart-lung transplantation or not. Ten heart-lung allografts (no immunosuppressive agent was given) and four isografts were examined pathologically. There was no pathologic change except perivascular or peribronchiolar edema in isografts, which was attributed to operative damage. Acute pulmonary rejection apparent pathologically 3 days after transplantation and lung allografts lost its function 6 days after transplantation. Otherwise, acute cardiac rejection first became apparent pathologically 5 days after transplantation. And their pulsation appeared well 6 days after it. It is concluded that pulmonary rejection precedes cardiac rejection following heart-lung transplantation.     

Time course and cellular localization of inducible nitric oxide synthases expression during cardiac allograft rejection

BACKGROUND: We have demonstrated that inhibition of inducible nitric oxide synthase (NOS) ameliorated acute cardiac allograft rejection. This study determined the time course and cellular localization of inducible NOS expression during the histologic progression of unmodified acute rat cardiac allograft rejection. METHODS: Tissue from syngeneic (ACI to ACI) and allogeneic (Lewis to ACI) transplants were harvested on postoperative days 3 through 10 and analyzed for inducible NOS mRNA expression (ribonuclease protection assay), inducible NOS enzyme activity (conversion of L-[3H]arginine to nitric oxide and L-[3H]citrulline), and nitric oxide production (serum nitrite/nitrate levels). Inducible NOS mRNA and protein expression were localized using in situ hybridization and immunohistochemistry. RESULTS: Inducible NOS mRNA and enzyme activity were expressed in allografts during mild, moderate, and severe acute rejection (postoperative days 4 through 10), but were not detected in normals, isografts, or allografts before histologic changes of mild acute rejection (postoperative day 3). Inducible NOS expression resulted in increased serum nitrite/nitrate levels during mild and moderate rejection (postoperative days 4 through 6). Inducible NOS mRNA and protein expression localized to infiltrating mononuclear inflammatory cells in allograft tissue sections during all stages of rejection but were not detected in allograft parenchymal cells or in normals or isografts. CONCLUSIONS: Inducible NOS expression and increased nitric oxide production occurred during the early stages of acute rejection, persisted throughout the unmodified rejection process, and localized to infiltrating inflammatory cells but not allograft parenchymal cells during all stages of acute rejection.     

Increased risk of antibody-mediated rejection of reduced-size liver allografts

Because of the shortage of liver allografts in children, transplantation of reduced-size liver allografts from adult cadaveric donors or living, related donors is being done more frequently. Reduced-size liver allografts may be used in cases of ABO incompatibility and T-cell warm cross-match positivity. This experimental study in inbred rats was undertaken to determine if reduced-size liver allografts are more sensitive to antibody-mediated rejection than full-size liver allografts. Brown-Norway (BN) (RT1(n)) rats were sensitized by three successive skin grafts at 10-day intervals. Then orthotopic Lewis (LEW) (RT1(1)) liver grafts were transplanted into these BN rats. Full-size liver allografts were compared with reduced-size liver allografts (70% of donor liver). Control groups were composed of full-size and/or reduced-size isografts. Titers of specific antibodies were assayed using a complement-dependent assay before and after orthotopic liver transplantation. Histological and immunofluorescence studies (IgG, IgM, C(3), and fibrinogen deposits) were assessed. Recipients of reduced-size liver allografts died of hyperacute rejection at 36.6 +/- 4.1 h, significantly earlier than recipients receiving full-size liver allografts, which died of accelerated acute rejection at 259.2 +/- 25.2 h (P < 0.001). Either full-size or reduced-size isograft recipients survived indefinitely. A decrease in the titers of donor-specific antibodies was observed in both groups of animals. Slight deposits of IgG, IgM, C(3), and fibrinogen were observed in recipients of reduced-size liver allografts, whereas larger deposits were observed in recipients of full-size liver allografts. Our data demonstrate that there is an increased risk of antibody-mediated rejection of reduced-size liver allografts in sensitized recipients. This may have important clinical implications for partial liver grafting in cases of ABO incompatibility and T-cell warm cross-match positivity.     

Hyperhomocyst(e)inemia Induces Accelerated Transplant Vascular Sclerosis in Syngeneic and Allogeneic Rat Cardiac Transplants

Chronic rejection (CR) and transplant vascular sclerosis (TVS) cause the majority of graft failures in cardiac transplantation. Hyperhomocyst(e)inemia [hH(e)] is associated with human TVS without a proven causal relationship. This study investigated the effect of hH(e) on graft survival and TVS in allogeneic and syngeneic rat cardiac transplants. Lewis recipients of heterotopic F344 heart allografts, received normal or hH(e)-inducing (folate, methionine) diets [controls: syngeneic transplanted [+/- hH(e), + CsA] and nontransplanted rats [+/- hH(e), +/- CsA]]. Serial plasma homocyst(e)ine [H(e)] levels were measured. TVS was assessed in clinically rejected grafts and a subset of pre-rejection normal diet allografts (day 64) (neointimal index, NI). The hH(e) diet elevated plasma H(e) levels. When compared with normal diet controls (n = 9), hH(e) diet allografts (n = 9) had decreased time to onset of CR (40 +/- 9 vs. 72 +/- 10d, p = 0.02), and graft failure (64 +/- 10 vs. 107 +/- 12d, p = 0.009). hH(e) diet allografts at rejection (n = 9, 64d) had more severe TVS (NI = 68 +/- 2) than both time-matched normal diet allografts (NI = 49 +/- 6, n = 8, 64d, p <0.001) and normal diet allografts at rejection (NI = 58 +/- 5, n = 9, 107d, p = 0.007). hH(e) induced TVS in syngeneic grafts (NI=50 +/- 3, n = 10 vs. NI = 5 +/- 3, n = 10, 130d, p <0.001). hH(e) accelerated rejection and increased the severity of TVS in allogeneic cardiac transplants, and induced TVS in syngeneic cardiac transplants.     

Use of anti-CD40 ligand monoclonal antibody as antirejection therapy in a murine peripheral nerve allograft model

Monoclonal antibody directed against CD40 ligand prevents acute allograft rejection in several models of solid-organ transplantation. This study describes the use of CD40 ligand as antirejection therapy in a mouse peripheral nerve allograft model. C3H mice received 8-mm nerve isografts (n = 2) or nerve allografts from C57BL donors. Treated animals (n = 11) received anti-CD40 ligand antibody applied to the graft and by intraperitoneal injections postoperatively. At 3 weeks, nerve histology from treated animals was comparable to isografts, whereas untreated allografts demonstrated virtually no signs of regeneration. Walking-track analysis demonstrated a trend toward improved functional recovery in treated animals. In conclusion, blockade of the CD40 pathway suppresses nerve allograft rejection in mice, and facilitates regeneration comparable to isografts.     

The effect of soluble complement receptor type 1 on hyperacute allograft rejection.

A major obstacle to successful organ transplantation in sensitized recipients is antibody-mediated hyperacute rejection. We hypothesized that human recombinant soluble complement receptor type 1 (sCR1), which inhibits activation of the complement cascade at multiple stages, would delay this process. Using a well-established model of hyperacute rejection, 21 Lewis rats each received three successive ACI rat skin grafts which resulted in high serum titers of ACI-specific antibodies. These hypersensitized Lewis rats then received heterotopic ACI cardiac allografts. Immediately prior to allograft reperfusion, sCR1 at 3 mg/kg (n = 11) or an equivalent volume of phosphate-buffered saline (PBS) (n = 10) was administered intravenously. Five minutes following allograft reperfusion, hemolytic complement activity was reduced by 63 +/- 2% (SEM) in the sCR1 group vs 25 +/- 3% in the PBS group (P less than 0.0001, Wilcoxon rank sum test (WRST)). Graft survival in the sCR1 group was prolonged to 32.0 +/- 4.47 hr vs 3.25 +/- 0.81 hr in the PBS group (P less than 0.0001, WRST). Serial histologic examination of allografts showed that sCR1 therapy prevented the early development of luminal platelet thrombi in the allograft coronary vessels. This study demonstrates that a single 3 mg/kg dose of sCR1 significantly prolongs ACI cardiac allograft survival in the hypersensitized Lewis rat recipient. Complement inactivation, mediated by sCR1, may prove useful for transplantation in sensitized recipients.     

Cold ischemia augments allogeneic-mediated injury in rat kidney allografts

BACKGROUND: Some clinical studies demonstrate that kidney grafts with prolonged cold ischemia experience early acute rejection more often than those with minimal ischemia. The mechanism, however, is putative. Therefore, the aim of this study was to unravel the impact of ischemia on the immune response in rat kidney allografts compared with that in isografts. METHODS: To induce ischemic injury, donor kidneys were preserved for 24 hours in 4 degrees C University of Wisconsin solution before transplantation. No immunosuppression was administered. The histomorphology according to the BANFF criteria for acute rejection and infiltrating cells were assessed at days 1, 2, 3, 4, 6, and 8 post-transplantation. RESULTS: In allografts, exposure of the kidney to ischemia led to a significantly earlier onset of interstitial cell infiltration and tubulitis compared with nonischemic allografts. The BANFF score of interstitial cell infiltration was 1 +/- 0 vs. 0.25 +/- 0.29 at day 3 and 2 +/- 0 vs. 1.25 +/- 0.25 at day 4. In contrast, in isografts, the effect of ischemia on the histology was not significant. From day 6, the histologic differences between ischemic and nonischemic grafts disappeared. Ischemia led to a more intense expression of P-selectin (day 1), intercellular adhesion molecule-1 (ICAM-1; day 2), and major histocompatibility complex (MHC) class II on endothelium and proximal tubular cells (day 2) in both allografts and isografts. Concurrently with the up-regulated ICAM-1 and MHC expression, significantly more CD4(+) cells and macrophages infiltrated the ischemic allografts at days 2 and 3 and the ischemic isografts at day 4. Importantly, the influx of these cells after ischemia was significantly greater in allografts than in isografts. CONCLUSIONS: Cold ischemia augments allogeneic-mediated cell infiltration in rat kidney allografts. The earlier onset of acute rejection in 24-hour cold preserved allografts may be prevented by better preservation or treatment using tailored immunosuppression.