| Islet transplantation has been hindered by continued failures secondary to immunological rejection and islet cell loss from a non vascularized graft. This thesis addresses strategies to improve islet cell transplantation through improved immunosuppression and gene transduction methodologies. We found that a monoclonal antibody against a protein expressed on all hematopoietic cells, CD45, results in long term allograft survival and tolerance in a murine model of islet cell transplantation. Anti-CD45RB mAb, is able to increase protein expression of a potent downregulatory molecule, CTLA-4 on CD4 T cells. This likely occurs through a non-transcriptional mechanism that is distinct from T cell receptor upregulation of CTLA-4. Tolerance that develops with anti-CD45RB mAb treatment is absolutely dependent on the expression of this protein, as molecules which interfere with its expression or knockout mice are unable to accept allografts. We also found that anti-CD45RB mAb ligation causes a rapid and substantial apoptosis of lymphocytes, primarily CD8 cells. This occurs even in the absence of T cell activation and may involve the Fas pathway. Furthermore, islet transplantation studies using knockout mice and adoptive transfer studies demonstrate an absolute requirement for T cell apoptosis in anti-CD45RB mAb induced graft acceptance.; To preserve islets from cell death, we transduced islets with an adenoviral vector containing the survivin gene. We found that islets were protected from cell death from cytokines and hypoxia in vitro and had improved function in a model of marginal islet transplantation in vivo.; Together this data provides new immunologic and non-immunologic methods to improve the success of islet cell transplantation that may one day be translated into the clinical arena. |
