DPP4 and type 1 diabetes mellitus: To investigate the potential mechanisms by which the DPPIV inhibitor MK626 induced a reduction in T1D incidence and insulitis score, we aimed to determine whether treatment with MK626 was associated with changes in T cell subsets from both the thymus and peripheral compartments (spleen and PLNs) and/or in their expression of CD26, which could contribute to the development of immune tolerance.