T-cell mechanisms of B-cell destruction

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In type 1 diabetes the body becomes deficient in insulin production from pancreatic b cells because the immune system mistakenly attacks and destroys b cells as if they were an invading infection. Recurrence of autoimmune destruction of b cells also occurs following transplantation of whole pancreas or islet cells and may occur in the future when other engineered insulin producing cells are transplanted. The focus of this program is to better understand how b cells are killed by the immune system and to test ways of protecting beta cells from these mechanisms. Because of the inaccessibility of the pancreas to study (particularly biopsy) in humans with diabetes, much of the proposed work will be carried out in b cells derived from non-obese diabetic (NOD) mice, the best available mouse model of type 1 diabetes. It is clear from the literature that a molecule called perforin found in cytoxic T lymphocytes (CTL) is a major, if not the major, mechanism the immune system uses against b cells. For this reason we will try to better understand the interaction between b cells and perforin and ultimately design ways of them from perforin-mediated cell death. It is equally clear that there are other mechanisms besides perforin that can cause b cell death and the program will also address discovery of these mechanisms and new ways to block them. Beta cells in NOD mice will be protected from perforin or other mechanisms by the addition of protective genes or removal of harmful genes using transgenic knockout technology. Addition or removal of genes involved in cell death can be done systematically and each protocol tested using NOD mouse model. The process of cell death that b cell undergo in type 1 diabetes is called apoptosis. Apoptosis is a general mechanism by which cells of all types die. Experts in the biology of apoptosis and perforin are important members of the program, providing the opportunity to translate the latest advances in cell death research to diabetes. This research addresses several of the specific research areas of interest to JDRF. It focuses on the prevention of b cell death in individuals with type 1 diabetes receiving islet transplants. It may be applicable in the future to protection of stem or precursor cells that have been differentiated into b cells or even to devising strategies to prevent the development of diabetes.