Type 1 diabetes mellitus (T1DM) is an autoimmune disease in which the person’s immune system destroys its own pancreatic islet cells that leads to complete loss of insulin production. Allogeneic pancreatic islet cell transplantation has been shown to replenish the vanished β-cell population and provide glycemic control, restoration of hypoglycemia awareness, and protection from severe hypoglycemic events. However, with allogeneic transplantation, there is a need for life-long immunosuppression to protect the islet grafts from allo- and autoimmunity.