Protective effects of green tea in suppressing autoimmune response in Type 1 Diabetes

Abstract

Autoimmune disease onset and progression involves both genetic and environmental factors. Dietary factors are modifiable environmental factors that affect the outcome of autoimmune diseases. Populations that consume green tea (GT) have one of the lowest T1D disease incidence, thus GT potentially can prevent/blunt autoimmune responses. However, how GT modulates immune functions and suppress autoimmunity is unclear. Type 1 diabetes (T1D) is a model for studying the effects of GT on autoimmune diseases. We hypothesize that GT suppress T1D autoimmune response by restoring immune regulation. We characterized the effects of GT on T1D using nonobese diabetic (NOD) mice which develop spontaneous T1D. NOD mice were provided with 2% GT or water. After 5 wks, we examined the extent of insulitis in the pancreas. GT‐treated NOD mice had significant reduced insulitis compared to control. We hypothesize that GT suppressed insulitis by directly affecting regulatory T cells (Treg) and dendritic cells (DC), both critical in controlling autoimmunity. Indeed, GT‐treated NOD mice had 1) increased Treg frequency, 2) decreased DC TNFalpha production, and 3) reduced T cell proliferation and IFNgamma production. Our data suggest GT has potent immunomodulatory effects on multiple cell types in vivo, and provides the foundation for understanding the mechanisms by which GT modulate autoimmune response and immune function in general.