In the case of T1D, it is conceivable that a precipitating event such as nonspecific inflammation, metabolic stress, smaller pancreas size [35], or a viral infection [36] activates modifying enzymes such as tTG in beta cells and within tissue resident APC, thereby generating modified beta cell proteins that are recognized by the immune system (Fig. 1). Here, TGM2 is linked to type 1 diabetes mellitus.