Castanospermine, an oligosaccharide processing inhibitor, reduces membrane expression of adhesion molecules and prolongs heart allograft survival in rats.

The inhibition of intracellular oligosaccharide processing is a new approach to immunosuppression in allotransplantation. The net effect of such inhibition is reduction in the membrane expression of certain glycoproteins. Hence cell-cell interaction in allorejection may be impaired in the presence of glycoprotein processing inhibitors because the expression of key ligand-receptor pairs of N-linked glycoproteins including adhesion molecules is inhibited. The aims of this study were to measure the immunosuppressive ability of castanospermine (CAST) in a rat heart allograft model, to measure its effect on membrane expression of adhesion molecules (LFA-1 alpha, LFA-1 beta, ICAM-1), class I and class II MHC antigens and on other T cell associated molecules (CD4, CD8, CD39, CD45, W3/13), to test its tolerogenic potential and its toxicity. Membrane expression of these molecules was measured by flow cytometry for single cells and by immunoperoxidase staining for the allograft. In grafted rats CAST significantly reduced the expression of LFA-1 alpha on lymphoid cells in the thymus, lymph node, spleen and heart allografts. ICAM-1 expression on endothelial cells of the allograft vasculature, class I and class II MHC expression on lymphoid cells in the thymus, class II MHC expression on lymphoid cells in the allograft; and CD4, CD8, CD45 and W3/13 expression on lymphoid cells in some organs. By contrast, in non-grafted rats CAST significantly upregulated expression of class I MHC and CD45 in the thymus, lymph node and spleen, ICAM-1 and CD4 on lymphoid cells in the spleen, but reduced expression of LFA-1 alpha on lymphoid cells in the thymus. It also prolonged rat heart allograft survival in a dose-dependent manner and with limited testing was relatively non-toxic. In conclusion, CAST is an immunosuppressive molecule which may work by downregulation of the ligand-receptor adhesion molecule pair, LFA-1 alpha-ICAM-1 although subtle downregulation of class I and II MHC, CD4 and CD8 molecules could also contribute to its immunosuppressive activity. Hence, both lymphocyte-endothelial cell binding and lymphocyte activation may be inhibited by CAST. This work suggests that CAST may hold significant potential as a transplant immunosuppressant probably as an adjuvant agent to inhibitors of interleukin 2 secretion.

Behavioral conditioning prolongs heart allograft survival in rats.

Conditioned immunosuppression using a taste aversion paradigm has been demonstrated in a number of laboratory models but few reports have demonstrated changes in immunity sufficient to be of clinical relevance. The experiments reported here demonstrate that the survival of heart allografts in rats can be prolonged by behaviorally conditioned immunosuppression using cyclosporin A (CsA) as an unconditioned stimulus in taste aversion conditioning. Conditioned animals received saccharin as the conditioned stimulus paired with an injection of CsA at 10 and 6 days prior to transplantation. They were reexposed to saccharin alone 1 day prior to and 3 days after transplantation. On these occasions the conditioned group displayed taste aversion behavior when offered saccharin and a significant prolongation of heart graft survival was observed compared to the conditioned and nonconditioned control groups. These experiments suggest that behaviorally conditioned immunosuppression may have important clinical implications as an adjunct to drug treatments in transplantation medicine.

[Revascularization of peripheral nerve transplants. Stereomicroangiographic evaluation of revascularization in allogeneic transplants, allogeneic transplants with cyclosporin A therapy and autologous transplants]. / Revaskularisierung peripherer Nerventransplantate. Stereomikroangiographische Beurteilung der Revaskularisierung bei allogenen Transplantaten, allogenen Transplantaten unter Cyclosporin A-Therapie und autologen Transplantaten.

Allogeneic nerve grafts of the sciatic nerve longer than 3 cm were transplanted between August- and Wistar rats. One group of animals were treated with 17 mg/kg body weight Cyclosporine A from day 1-28. Autologous nerves served as controls. At various postoperative days contact microangiography, stereoangiography, microdensitometry and histology were performed. Allogeneic untreated grafts were rejected at day 7. Undisturbed neovascularisation was only seen in autografts. In Cyclosporine A treated rats a gradually reduced revascularisation could be observed until day 90.

[Cellular mechanisms in graft rejection of peripheral nerve transplants]. / Zelluläre Mechanismen bei der Abstossungsreaktion peripherer Nerventransplantate.

Allogeneic nerve specimens (sciatic nerve) were transplanted in rats. Cyclosporin A was used as an immunosuppressive agent. Under this treatment reinnervation occurred. Without treatment, nerve grafts were rejected. In order to monitor the acute cellular rejection, the nerve grafts were surrounded by a silicon tube. The perineural exudate and the mononuclear cells contained in it were aspirated at three day intervals by fine needle aspiration. Exact analysis of the mononuclear cells involved in the rejection mechanism and their degree of activation could in future provide a tool that allows control of nerve graft rejection and estimation of the effect of immunosuppressive treatment.