OBJECTIVE The progressive infiltration of pancreatic islets by lymphocytes is mandatory for development of autoimmune type 1 diabetes. This inflammatory process is mediated by several mediators that are potential therapeutic targets to arrest development of type 1 diabetes. In this study, we investigate the role of one of these mediators, interleukin-16 (IL-16), in the pathogenesis of type 1 diabetes in NOD mice.
RESEARCH DESIGN AND METHODS At different stages of progression of type 1 diabetes, we characterized IL-16 in islets using GEArray technology and immunoblot analysis and also quantitated IL-16 activity in cell migration assays. IL-16 expression was localized in islets by immunofluorescence and confocal imaging. In vivo neutralization studies were performed to assess the role of IL-16 in the pathogenesis of type 1 diabetes.
RESULTS The increased expression of IL-16 in islets correlated with the development of invasive insulitis. IL-16 immunoreactivity was found in islet infiltrating T-cells, B-cells, NK-cells, and dendritic cells, and within an insulitic lesion, IL-16 was derived from infiltrating cells. CD4+ and CD8+ T-cells as well as B220+ B-cells were identified as sources of secreted IL-16. Blockade of IL-16 in vivo protected against type 1 diabetes by interfering with recruitment of CD4+ T-cells to the pancreas, and this protection required the activity of the chemokine CCL4.
CONCLUSIONS IL-16 production by leukocytes in islets augments the severity of insulitis during the onset of type 1 diabetes. IL-16 and CCL4 appear to function as counterregulatory proteins during disease development. Neutralization of IL-16 may represent a novel therapy for the prevention of type 1 diabetes.
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- Received January 28, 2009.
- Accepted July 27, 2010.
- © 2010 by the American Diabetes Association.
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