Previous studies in mice and humans suggesting that γδ T cells play a role in the development of type 1 diabetes have been inconsistent and contradictory. We attempted to resolve this for the type 1 diabetes-prone NOD mice by characterizing their γδ T cell populations, and by investigating the functional contributions of particular γδ T cells subsets, using Vγ-gene targeted NOD mice. We found evidence that NOD Vγ4+ γδ T cells inhibit the development of diabetes, and that the process by which they do so involves IL-17 production and/or promotion of regulatory CD4+ αβ T cells (Tregs) in the pancreatic lymph nodes. In contrast, the NOD Vγ1+ cells promote diabetes development. Enhanced Vγ1+ cell numbers in NOD mice, in particular those biased to produce IFNγ, appear to favor diabetic disease. Within NOD mice deficient in particular γδ T cell subsets, we noted that changes in the abundance of non-targeted T cell types also occurred, which varied depending upon the γδ T cells that were missing. Our results indicate that while certain γδ T cell subsets inhibit the development of spontaneous type 1 diabetes, others exacerbate it, and they may do so via mechanisms that include altering the levels of other T cells
