The Kang Lab is interested in the development of novel strategies for the induction of transplant-specific tolerance in order to control transplant rejection without long-term global immunosuppression. We have several projects that each focus on different means of achieving this ultimate goal. In one project, we are working with specialized immune cells called dendritic cells to learn how to specifically suppress only the white blood cells that attack the transplanted organ in a recipient. Other developments include genetically engineering cell lines in order to determine quantitative and mechanistic information about the roles of two different types of white blood cells in rejection.
Generation of Tolerance to Alloantigen
In order to achieve allo-specific transplant tolerance, we are currently investigating the manipulation of dendritic cells (DCs), which are specialized immune cells that normally activate the T cells that cause rejections. The lab has succeeded in genetically engineering dendritic cells to express well-known immunomodulatory molecules (interleukin 10, TGF_beta, CTLA4 Ig); these modified DCs appear to specifically inhibit donor-specific T cells in vitro. A major emphasis of our work is on targeting DCs to lymphoid organs (such as lymph nodes and spleen) via engineered expression of lymphoid homing receptors (CCR7, L-selectin, or a control molecule green fluorescent protein).
We are testing the best homing receptor (or combination of homing receptors) by injecting modified DCs intravenously into mice, followed by an analysis of their lymphoid homing efficiency at various time points. We believe that lymphoid homing will be critical to the induction of tolerance. Once our homing strategy is defined, this will be combined with immunomodulatory genes using bicistronic vectors (gene vehicles that can express more than one gene). Once these DCs have been successfully engineered as confirmed by in vitro testing, we will inject them into mice that will be the recipients of islet transplants, and we will monitor the results to see if the dendritic cell treatment prolongs survival of these grafts.
Development of a T Cell Receptor Transgenic Model
Basic research has shown that T cells appear to be key mediators of transplant rejection. However, despite their apparent importance, little quantitative or mechanistic information is known about the relative contributions of CD+4 T cells and CD8 T cells to the process of transplant rejection. One method of studying the role of these particular T cells is to design mice to produce T cells bearing a known specificity to as given antigen. These mice are called T cell receptor transgenic mice, and their use has revolutionized the study of T cell immunology in vivo. We have created a T cell receptor transgenic mouse that carries CD4+ T cells with reactivity to allografts. These mice, in combination with previous established transgenic/knockout mouse lines, will be used to study parameters including the minimum numbers of each subset of T cells needed for rejection, spatial-temporal characteristics of rejection, the contribution of T cell memory rejection, molecular requirements for rejection, and the development of a mechanistic "readout" for transplantation tolerance strategies.