Using T-Cell Alloreactivity and Chimerism to Guide Immunosuppression Minimization in Intestinal Transplantation
brief summary
The purpose of this study is to investigate the safety and feasibility of giving intestinal transplant patients CD34+ stem cells (the cells that make all the types of blood cells) obtained from their organ donor's bone marrow. The goal of this is to develop a post-transplant treatment strategy that controls rejection while reducing the high risk of infection and malignant disease associated with the high levels of immunosuppression medication(s) that intestinal and multi-organ transplant patients must take. Infusion of bone marrow cells from the same donor of the transplanted organ(s) could promote a state called "mixed chimerism" in which both donor cells and recipient cells coexist in the body with the ultimate goal of minimizing the amount of immunosuppression medication(s) needed.
detailed description
Abdominal trauma, congenital abnormalities and ischemic injury cause intestinal damage that prevents the digestion and absorption of fluids and nutrients essential for life. Intestinal transplantation is life-saving for patients with complications related to the administration of intravenous nutrients. Approximately 100-160 intestinal transplants (ITx) are performed in the US annually. However, patient survival rates are far from optimal, due to high rejection rates resulting from an immune attack of the recipient against the donor, termed host-vs-graft (HVG) reactivity The high levels of global immunosuppression used to prevent rejection come with a high risk of infections and malignant disease (i.e. lymphoma). Thus, there is an urgent need for a well-tolerated treatment strategy that controls rejection while reducing these risks. Immune tolerance, in which the immune system regards the donor as "self" so that long-term graft acceptance is achieved without life-long immunosuppression, would accomplish this goal . Infusion of bone marrow cells from the same donor of the solid organs could promote a state called "mixed chimerism" in which both donor cells and recipient cells coexist in the body. Mixed chimerism has been shown to induce tolerance to the transplanted organ in animal models and in patients receiving kidney transplants.
The investigators propose studies to promote tolerance induction in intestinal transplant recipients by administering donor bone marrow stem cells to promote lasting mixed chimerism. The investigators' proposal builds on their demonstration that mixed chimerism commonly occurs in intestinal transplant (ITx) recipients without bone marrow transplant, and that its presence correlates with reduced rejection rates. However, this mixed chimerism is not permanent. The investigators have discovered that there are bone marrow stem cells in the donor intestinal grafts and that some of these survive and enter the bone marrow of the recipient. This process is facilitated by a phenomenon called a "lymphohematopoietic graft-vs-host responses (LGVHR)", in which T lymphocytes from the ITx donor attack recipient blood-forming cells to make "space" for their own establishment in the bone marrow, but do not induce GVHD. The investigators have also obtained evidence that this immune response suppresses rejection of the graft.