What causes people to get type one diabetes?

Auutoimmunity. Autoimmunity refers to one's own immune system making antibodies that target one's own proteins or tissues. T1d(type1 diabetes) occurs when antibodies lead to destruction of beta cells in the pancreas that produce insulin. Researchers are working on exactly what leads to autoimmunity. It appears to be a combination of genetics and exposure to certain viruses or food/environmental proteins.