Infiltration of autoreactive CD4 T lymphocytes into the pancreas represents a hallmark event in the development of insulin-dependent autoimmune diabetes. Chemokines regulate adhesion of cells to vascular endothelium and, via chemoattractant effects, govern cellular recruitment into inflammatory lesions. However, their role in diabetes has not yet been studied. Defining functions of chemokines in regulating inflammation in the pancreas will provide a greater understanding of diabetes and may supply essential new information for advances in treatment. Th1 cells which secrete IFN-gamma, TNF-alpha, and LT are associated with pathogenesis leading to destruction of islet beta cells and disease onset whereas Th2 cells which produce IL-4, IL-5 and IL-10 do not cause disease due to protective effects of IL-4. Early events leading to differences in the entry of autoreactive CD4 subsets into the pancreas may thus be crucial in diabetes and a key point for therapeutic intervention. The investigators have developed an adoptive transfer model to study the migratory behavior islet-specific, transgenic CD4 subsets. Th1 cells, which induce disease within 5-6 days, enter the pancreas more rapidly than Th2 cells and express different chemokines in vitro. Moreover, in vivo, several chemokines partition with Th1 but not Th2 infiltrates. From these studies they propose that polarized secretion of chemokines by Th1 vs. Th2 cells in the pancreas regulates selective recruitment of subsets of cells that determine whether beta islet cells are destroyed. This pilot project will employ several novel strategies to bridge in vitro and in vivo analysis of chemokines in diabetes that will form the basis for more detailed mechanistic studies in the future. They will use blocking studies to identify chemokines that regulate disease onset and progression, and intravital microscopy to assess chemotaxis in vivo in the presence or absence of Ag (islets). Since cytokines regulate chemokine synthesis by multiple cell types, cytokine/chemokine cascades are likely to determine the nature and extent of pancreatic inflammation. The investigators will test the hypothesis that T cell-derived cytokines coordinate chemokine expression and responses within the pancreas. In addition to IL-4 and IFN-gamma, they have an unparalleled opportunity to study TNF family cytokines (TNF-alpha, LT, LT alpha1beta2, LIGHT) using Fc-receptor constructs as blocking agents in experiments that are likely to reveal fundamental aspects of the biology of inflammation. They will determine if cytokines or conditions of TCR stimulation and costimulation can modulate a Th1 to a Th2 pattern of chemokine expression/reactivity and alter their capacity to induce diabetes. Identifying the role of chemokines in diabetes will provide new insights into regulation of the disease process.
