DPP4 and type 1 diabetes mellitus: Although data on DPP-4i impact in immune cells of T1D patients remain limited, Varga and colleagues discovered that in T1D patients, serum DPP-4 enzymatic activity is elevated, but mDPP-4 expression on lymphocyte membranes is reduced, which may indicate a novel T effector cell regulatory malfunction (Varga et al, 2011).