The immune system evolved to defend against infections (‘non-self’). When its control systems fail and it attacks ‘self’ tissues (that is, which belong to the organism to which the immune system belongs), the result is autoimmune disease. Genes and environment predispose to autoimmune disease. Some autoimmune diseases (Graves’ disease, hyperthyroidism, myasthenia gravis, systemic lupus erythematosis) are caused by antibody proteins secreted by immune B cells; others (type 1 diabetes, multiple sclerosis, rheumatoid arthritis) are due to toxic immune T cells – Professor Leonard C Harrison