Date of Award
2008
Degree Type
Thesis
Degree Name
Doctor of Philosophy
Program
Microbiology and Immunology
Supervisor
Dr. Terry Delovitch
Abstract
Autoimmune Type 1 diabetes (TlD) results from the T cell-mediated destruction of insulin-producing islet β cells of the pancreas. The most widely investigated pre- clinical animal model for the study of TlD is the nonobese diabetic (NOD) mouse, which spontaneously develops T1D with an immunological profile similar to the human disease. It is well accepted that T1D arises in part from functional deficiencies in regulatory T cell populations, including CD4+CD25+Foxp3+ (Treg) cells and iNKT cells. We and other investigators have shown that activation of iNKT cells by alpha-galactosylceramide (α- GalCer) can protect NOD mice from T1D. As iNKT cells represent a unique target for cellular therapy against T1D, the mechanisms underlying this protection warrant further examination.
My studies presented here examine the role of soluble mediators and cellular interactions that occur during iNKT cell mediated protection against T1D. Using NOD.IL-4 and NOD.IL-10/ mice, I found that IL-4 but not IL-10 expression was necessary for α-GalCer mediated protection against spontaneous and cyclophosphamide (CY) induced T1D. These results highlight an important role for IL-4 in iNKT cell induced protection against T1D. To further evaluate the mechanism of iNKT cell mediated protection against T1D, I analyzed whether the activity of CD4+CD25+Foxp3+ regulatory T cells (Tregs) was required for protection. Using treatment in vivo with an anti- CD25 mAb that inactivates Treg cells, I found that Treg activity is required for iNKT cell protection from T1D induced by α-GalCer. Treg inactivation prior to α-GalCer treatment resulted in increased pro-inflammatory cytokine release and bystander cell
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transactivation. I further explored whether this requirement for Treg activity also applies to a Th2 biased glycolipid analog of α-GalCer, termed C20:2. Unlike α-GalCer, Th2 biased activation of iNKT cells protected NOD mice from T1D following Treg cell inactivation. By comparison to α-GalCer, C20:2 activated iNKT cells secreted an increased level of Th2 cytokines and elicited reduced bystander activation of immune cells. These results suggest that Treg inactivation unmasks the potential side effects of α- GalCer and highlight the potential benefit of Th2 biased iNKT cell activation by C20:2 for the immunotherapy of TlD in humans
Recommended Citation
Ly, Dalam, "MECHANISMS OF INKT CELL PROTECTION AGAINST TYPE 1 DIABETES" (2008). Digitized Theses. 4929.
https://ir.lib.uwo.ca/digitizedtheses/4929