Type 1 diabetes, coeliac disease, autoimmune gastritis and thyroiditis are examples of autoimmune conditions where the immune system mistakenly responds to, and attacks, healthy cells of the body. Individually autoimmune diseases are relatively rare, but together they affect at least 5% of the UK population. The immune response that causes these diseases includes the production of antibodies to cells of the pancreas, gut, and thyroid. These antibodies can be measured in the blood and can act as markers of disease before symptoms occur. The antibodies to cells of the pancreas are highly predictive for type 1 diabetes; when an individual has multiple markers they have a 50-70% risk of developing diabetes in the next decade. These markers can be detected in early life (from 6 months of age) but may arise later and often persist for many years before disease onset. Although markers of autoimmunity have been well studied in family members of individuals with autoimmunity, particularly in childhood, they are rarely studied in people without a family history of disease. Studying markers of pancreatic and co-existing autoimmunity in blood samples from ALSPAC children and parents will complement data from our family-based study and tell us whether some people develop these markers during childhood, adolescence or in later life. Is autoimmunity “explosive” with rapid appearance of autoantibodies followed by clinical onset of symptoms or does it follow a more indolent pathway? This will help us understand why different individuals are diagnosed with autoimmune disease very early in life, while others are diagnosed as adults.