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The aim of this study was to determine if human decay-accelerating factor (hDAF) protects against hyperacute rejection in an ex vivo liver perfusion system using human blood. Pig livers were perfused ex vivo via the portal vein for an average of 5-6 h using a membrane oxygenator. Three groups were studied. Group I: Wild-type pig livers were alloperfused with fresh pig blood (n = 5). Group II: Wild-type pig livers were xenoperfused with fresh human blood (n = 5). Group III: hDAF transgenic pig livers were xenoperfused with fresh human blood (n = 5). The graft ischemic time, ratio of perfusate volume to liver weight, flow rate, and perfusate hematocrit were similar in each group. The hDAF livers perfused with human blood (Group III) had a lower ALT level, less protein and albumin losses, lower bilirubin levels in the perfusate, less weight gain, and greater bile production than the wild-type livers perfused with human blood. Histology showed classic features of hyperacute rejection in Group II, including massive hemorrhage, severe vasculitits, fibrin and C5b-9 deposition, and endothelial damage within 1 h of perfusion, whereas liver histology studies in Groups I and III were near normal. IgG and IgM deposits were seen in the xenoperfused livers. Electron microscopy (EM) and immuno-EM showed loss of endothelial cells, trapping of white blood cells and platelets, and diffuse fibrin deposits in Group II only. hDAF pig livers perfused with human blood showed superior function and histology when compared with wild-type pig livers. These data suggest that (1) hyperacute rejection may contribute to the inconsistent results using wild-type pig livers for extracorporeal liver support and (2) genetically modified pigs that express hDAF may provide a better donor source than wild-type pigs for extracorporeal liver support.

Post-transplantation lymphoproliferative disorder (PTLD) and acute rejection are two serious complications of orthotopic liver transplantation that can have a similar histologic appearance. We undertook the present study to assess the best way to distinguish these two entities. We studied histologic features, immunophenotyping, and Epstein-Barr virus (EBV) status, as assessed by immunohistochemical stain and in situ hybridization (ISH), in three groups: Group I, 8 cases of PTLD post-orthotopic liver transplantation with liver involvement; Group II, 15 cases diagnosed with acute liver rejection (control group); and Group III, a subset of 6 biopsy specimens from 4 patients of Group I whose graft rejection was diagnosed within the 2 months preceding the diagnosis of PTLD. The mean proportion of plasma to plasmacytoid cells in most cases from Group I was more than 40%, whereas from Group II it was less than 25% (P = .0001). There was a higher number of B lymphocytes than T lymphocytes in Group I. The numbers of mitotic figures and immunoblasts were significantly different in the two groups (P < .0001 and P = .0005, respectively), being higher in the patients with PTLD. EBV immunostain was most specific for the diagnosis of PTLD (75% positive in Group I, negative in Group II). ISH for EBV-encoded RNA was positive in 87% of cases in Group I and only 6.6% of cases in Group II (P = .0005). In Group III, four of the six liver biopsy specimens had a low plasma cell count and were negative for EBV studies. The other two biopsy specimens in this group had 70 to 80% plasma cell infiltrate, in addition to positive EBV immunostain and ISH in one, for which tissue was available for study. We conclude that viral studies and assessment of the number of plasma cells and B lymphocytes can help to distinguish between acute rejection and early PTLD.

Rejection continues to be the single largest impediment to successful organ transplantation. Antilymphocyte globulin, which contains antibodies that react with the leukocyte common antigen known as CD45, has proved to be one of the most effective agents for preventing rejection. We have shown earlier that a monoclonal antibody directed against the RB isoform of CD45 substantially inhibits the alloreactivity of human CD4+ lymphocytes in vitro. Here we investigate whether CD45RB could be an appropriate target for preventing renal allograft rejection in mice. Mice treated with two injections of a monoclonal antibody (MB23G2) raised against CD45RB protein all survived and had normal renal function. Furthermore, this antibody reversed acute rejection when therapy was delayed until day 4, and the mice survived for their natural lifespan. The immunosuppression achieved may find application in the prevention and treatment of transplant rejection in man.

Rapid and severe rejection remains a major obstacle to successful clinical intestinal transplantation (IT). The aggressive nature of rejection in IT has been attributed to the increased massive immune stimulus provided by large numbers of resident lymphocytes, antigen presentation capacity of enterocytes, and graft damage mediated by luminal microflora. Early small bowel expression of proinflammatory cytokines, MHC class II, and adhesion molecules may also promote IT rejection, but the lack of a mouse model has hampered extensive studies of gene expression in IT. Using a recently developed surgical model, we examined the temporal pattern of gene expression in CB6F1 (H-2b/d) vascularized, heterotopic intestinal allografts transplanted into BALB/c (H-2d) mice. Although histological evidence of rejection was not present until day 7 in allografts, Northern blot analysis demonstrated increases in TNF alpha gene transcripts as early as day 3, followed by the expression of IL-1 beta, intercellular adhesion molecule-1, and MHC class II by day 5. Using reverse-transcriptase polymerase chain reaction, IFN-gamma was detected in allografts by day 3 and persisted to day 10. In contrast, IL-2, IL-4, IL-5, and IL-6 mRNA transcripts peaked by day 5 and then decreased, suggesting that both Th1 and Th2 subsets are involved in the rejection of unmodified small bowel allografts. The early and progressive expression of TNF alpha and IL-1 beta as well as IFN-gamma, intercellular adhesion molecule-1, and MHC class II in IT rejection may contribute to the difficulty in controlling IT rejection with present immunosuppression.

Colon transplantation has been proposed as a method to improve the function of an intestinal allograft. The present study examined the risk of colon rejection and the effect of FK506 on colon rejection in BN-->LEW rats with orthotopic bowel transplants. The first 4 groups included rats with untreated allografts (group 1), rats with isografts treated with 0.6 mg/kg FK506 (group 2), rats with allografts treated with 0.6 mg/kg FK506 (group 3), and rats with allografts treated with 0.4 mg/kg FK506 (group 4). In each of these groups (10-12 rats), half of the animals received a small bowel graft only (SB), while the other half received a small bowel, ascending colon, and cecum graft (SBC). The animals were followed daily until they died or were killed at 4 weeks. In group 5, an additional 18 untreated rats with SBC allografts were randomly killed on the third, fifth, seventh, and tenth postoperative days to study the sequential histopathologic and immunopathologic changes of colon rejection. There was no difference in survival, body weight, nutritional parameters, or bacterial contamination after SB and SBC transplantation. Intestinal transit was slower after SBC than SB transplantation (P < 0.05). Sequential histopathologic studies revealed that (1) the severity and time course of colon rejection was similar to small intestine rejection, and (2) the features of colon rejection were similar to ulcerative colitis. There was no evidence of graft-versus-host disease after SBC transplantation. In summary, adding a segment of large bowel to a small bowel allograft does not increase the risk of rejection or surgical complications. The transplanted colon slows intestinal transit. Treatment with FK506 effectively prevents colon rejection. These data suggest that adding a colon graft may improve the outcome of clinical small bowel transplantation.