Here we report that stable multilineage chimerism and engraftment can be established across haploidentical major histocompatibility complex barriers with minimal treatment-related toxicity and without significant risk of graft-versus-host disease.
Using the miniature swine large animal model we have attempted to determine the relationship between tolerance and the presence of donor cells in the bone marrow, thymus and lineages of peripheral blood in a series of hematopoietic cell transplant recipients receiving delayed donor allografts without immunosuppression. Twenty-two animals receiving hematopoietic cell transplantation and a delayed organ allograft were analyzed. Assays for presence of donor CFUs in bone marrow (by PCR), thymic chimerism (by FACS and PCR/Southern Blot), peripheral blood chimerism (by FACS), and in vitro responsiveness to donor MHC were performed. Presence of donor BM CFUs, thymic chimerism and multilineage peripheral blood chimerism at the time of organ transplantation all correlated precisely with subsequent allograft tolerance (p < 0.001, p < 0.001, p < 0.005 respectively). These parameters were therefore accurate predictors (Positive Predictive Value (PPV) = 100% in all) of tolerance. In vitro assays of responsiveness were also highly associated (p < 0.002, p < 0.002 respectively), but were not as accurate predictors of subsequent organ tolerance (CML PPV = 80%). Engraftment, as indicated by the presence of donor derived CFU in the bone marrow, detectable thymic chimerism and multilineage peripheral blood chimerism are reliable predictors of subsequent donor allograft acceptance in hematopoietic cell transplant recipients.
This manuscript reports on five cases of spontaneous myelogenous leukemia, similar to human disease, occurring within highly inbred, histocompatible sublines of Massachusetts General Hospital (MGH) MHC-defined miniature swine. In cases where a neoplasm was suspected based on clinical observations, samples were obtained for complete blood count, peripheral blood smear, and flow cytometric analysis. Animals confirmed to have neoplasms were euthanized and underwent necropsy. Histological samples were obtained from abnormal tissues and suspect lesions. The phenotype of the malignancies was assessed by flow cytometric analysis of processed peripheral blood mononuclear cells and affected tissues. Five cases of spontaneous myeloid leukemia were identified in adult animals older than 30 months of age. All animals presented with symptoms of weight loss, lethargy, and marked leukocytosis. At autopsy, all animals had systemic disease involvement and presented with severe hepatosplenomegaly. Three of the five myelogenous leukemias have successfully been expanded in vitro. The clustered incidence of disease in this closed herd suggests that genetic factors may be contributing to disease development. Myelogenous leukemia cell lines established from inbred sublines of MGH MHC-defined miniature swine have the potential to be utilized as a model to evaluate therapies of human leukemia.
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