In type 1 diabetes (T1D), the immune system mistakenly attacks the pancreatic islet β cells resulting in the loss of insulin secretion. Insulin-replacement therapy developed more than a century ago provided means to manage the symptoms of diabetes without addressing the root cause of the disease-the faulty immune system. A healthy immune system has built-in mechanisms to limit unwanted, excessive immune activation and prevents damages to self-tissues. These immune self-tolerance mechanisms are often impaired in autoimmune patients including those with T1Ds. Understanding how immune self-tolerance is broken in patients with T1D can inform the design of new curative therapies that correct the immune defects. In this paper, we will summarize the mechanisms of immune tolerance, review their relevance to T1Ds, and discuss novel therapeutic approaches to rebalance the immune system for the treatment of T1Ds.