Type 1 diabetes mellitus as a disease of the β-cell (do not blame the immune system?)

Abstract

Type 1 diabetes mellitus is believed to result from destruction of the insulin-producing β-cells in pancreatic islets that is mediated by autoimmune mechanisms. The classic view is that autoreactive T cells mistakenly destroy healthy (‘innocent’) β-cells. We propose an alternative view in which the β-cell is the key contributor to the disease. By their nature and function, β-cells are prone to biosynthetic stress with limited measures for self-defence. β-Cell stress provokes an immune attack that has considerable negative effects on the source of a vital hormone. This view would explain why immunotherapy at best delays progression of type 1 diabetes mellitus and points to opportunities to use therapies that revitalize β-cells, in combination with immune intervention strategies, to reverse the disease. We present the case that dysfunction occurs in both the immune system and β-cells, which provokes further dysfunction, and present the evidence leading to the consensus that islet autoimmunity is an essential component in the pathogenesis of type 1 diabetes mellitus. Next, we build the case for the β-cell as the trigger of an autoimmune response, supported by analogies in cancer and antitumour immunity. Finally, we synthesize a model (‘connecting the dots’) in which both β-cell stress and islet autoimmunity can be harnessed as targets for intervention strategies. This Review examines the evidence that β-cells are active participants in the dialogue with the immune system during the development of type 1 diabetes mellitus. The authors suggest that therapies targeting β-cell health, vitality and function might prove essential, in combination with immunotherapy, to change the course of events leading to β-cell destruction. Autoreactive T cells are part of the normal T cell repertoire. β-Cells are poorly equipped to survive an inflammatory milieu and participate in their own destruction. Metabolic activity drives β-cell dysfunction and destruction. Inflammation triggers profound metabolic, epigenetic and autoantigenic changes, which expose β-cells to the immune system. The immune response to distressed β-cells might be one with ‘good intentions’, as infected tissues or tumours provoke the immune system in similar ways. Immunotherapy might be insufficient to cure type 1 diabetes mellitus; β-cell therapy might contribute to reducing β-cell immunogenicity and islet autoimmunity. Autoreactive T cells are part of the normal T cell repertoire. β-Cells are poorly equipped to survive an inflammatory milieu and participate in their own destruction. Metabolic activity drives β-cell dysfunction and destruction. Inflammation triggers profound metabolic, epigenetic and autoantigenic changes, which expose β-cells to the immune system. The immune response to distressed β-cells might be one with ‘good intentions’, as infected tissues or tumours provoke the immune system in similar ways. Immunotherapy might be insufficient to cure type 1 diabetes mellitus; β-cell therapy might contribute to reducing β-cell immunogenicity and islet autoimmunity.