ADA and type 1 diabetes mellitus: Although it is likely that mild ADA-SCID promotes a dysregulated immune system and therefore an increased risk for an autoimmune attack on beta-cells and subsequent T1D (3), the present findings support the notion that a decreased adenosine disposal rate, caused for example by a lowered ADA1 activity, initiates non-autoimmune apoptosis/necrosis also in beta-cells, and not only in lymphocytes, and that this could contribute to the pathogenesis of T1D.