Observation of some of the phenomena of tolerance to soluble protein antigens and allogeneic tissue transplants in Xenopus laevis has formed the framework of the present study. The method of larval induction of high-zone tolerance used in this laboratory has been confirmed and further analysed. Larvae treated with high doses of Human-γ-globulin (HGG) were unable to produce anti-HGG antibody after challenge. The proliferative response demonstrated in the spleens of tolerant toadlets 21 days after challenge was, however, of similar magnitude to that in normally responding animals. Adoptive transfer of high-zone tolerance specific to HGG was demonstrated by intravenous inoculation of tolerant histocompatible splenocytes simultaneously with an antigenic challenge via the dorsal lymph sac. This is indicative of the active involvement of a suppressor T-cell population. The induction of high-zone tolerance in X. laevis results in changes in spleen cell populations as demonstrated by buoyant density gradient separation. Spleen cell sub-populations taken from the separated layers were not, however, effective in the adoptive transfer of tolerance. A normal lymphocyte transfer reaction was observed in X. laevis to show a number of characteristics seen in the mammalian reaction. The use of mitomycin-C treated donor cells and early thymectomized hosts has demonstrated that the phenomenon is composed of donor and host components which are largely distinct from each other. Implantation of allogeneic larval spleens resulted in the induction of transplantation tolerance or impaired rejection in a significant proportion of skin grafted toadlets in which both the donor and host larvae were up to and including stage 51 at the time of transplantation. The implication of these results is that immunomaturity of the donor and host is important in the induction of transplantation tolerance but that other factors must also be involved.

No description available.

In this study we have reproduced the prolongation of graft survival by ITI in a rat heart transplant model in which an ITI of an optimal number of donor bone-marrow cells (BMC) was given together with 1ml ALS IP 14 days before transplant. The efficacy of this protocol was critically dependent on the donor-recipient haplotype and influenced by antigenic strength and MHC disparity but not by non-MHC background genes. In strain disparities where ITI was unsuccessful, this was caused by alloreactive recent thymic emigrant cells. In a high responder strain combination the effect was highly dependent on the dose of BMC in the intrathymic injection. Moreover it was readily reproduced with injection of antigen by the intravenous route, even at a lower dose than that required via the intrathymic route. This was in contrast to the other strain combinations tested in which the beneficial effect of donor antigen injection was specific to the intrathymic route, and it suggested that the effect in this group might be at least partly dependent on peripheral mechanisms. The polyclonal ALS can easily be demonstrated to be non-specific in its depletion of peripheral lymphocytes at the dose used in these studies, and we have shown that it also penetrates the thymus. Therefore treatment with ALS may have more effects that mere disablement of peripheral alloreactive T cells, thus complicating the interpretation of the experiments. We have therefore refined our model by recruiting in place of ALS a more specific agent, the partially depleting anti-CD4 monoclonal antibody MRC-OX38, which is equally effective as an adjunct to ITI. We have shown using flow cytometry and immunohistochemistry, that this and certain other monoclonal antibodies, at a therapeutic dose, do not cross the "blood-thymus barrier", and therefore do not complicate the model as ALS potentially does. We would recommend this approach in further studies.

The primary obstacle to enabling wide spread adoption of composite tissue transplantation, as well as to improving long term solid organ transplant outcomes, is establishing a personalized medication regimen optimizing the balance between immunosuppression and immune function the individual minimum effective level of immunosuppression. Presently, the clinical gold standard for monitoring immune function is histologic inspection of biopsy for tissue damage, or monitoring blood chemistry for signs of organ failure. These trailing indicators reflect damage that has already accumulated, and are of little use in proactively determining the immunologic state of a patient. Samples collected from small animal surgical models were used to quantify the amount of immune signaling protein present (cytokines and chemokines) under various experimental conditions. Patterns in protein expression that reliably discriminate amongst the groups were then investigated with statistical inference methods such as the logistic classifier, decision tree, and random forest, operating in both the original feature space and in transformed feature spaces. This work demonstrates computational methods are effective in elucidating and classifying cytokine profiles, allowing the detection of rejection in composite tissue allografts well in advance of the current clinical gold standard, and shows that the methods can be effective in solid organ contexts as well. This work further determines that cytokine patterns of inflammation associated with rejection are specific to the structure and composition of the tissue in which they occur, and can be distinguished from immune signaling patterns associated with unspecific inflammation, wound healing, or immunosuppressed tissue. Clinical translation of these findings may provide novel computational tools that enable physicians to design personalized immunosuppression strategies for patients. The methods described in this work also provide information that can be used to investigate the biological basis for the observed immune signaling patterns. Further development may provide a computational framework for identifying novel therapeutic strategies in other pathologies.