The human immune system defends us against invading microbes, viruses and even our own cells when they turn cancerous. But it can also be our own worst enemy. We now know that the immune defences can in fact turn attacker on the body’s cells in an aberrant phenomenon known as “autoimmunity”. In fact, many common illnesses today are autoimmune diseases, such as rheumatoid arthritis, type-1 diabetes and multiple sclerosis.
The first scientist to recognise autoimmunity — although he didn’t give it that name — was Hakaru Hashimoto, a young Japanese researcher who in 1912 described the cases of four middle-aged women with swollen thyroid glands. He extracted samples of their thyroid tissue while working at the medical school of Khyushu University in Japan and was struck by the preponderance of lymphoid cells within the biopsies. He ruled out chronic infections or deficiencies in the diet as the cause of the problem. Instead, in a 30-page monogram published in German he described what he thought was a new disease, which he called struma lymphomatosa.
Hashimoto’s disease is now recognised as an autoimmune disease, occurring twice as often in women than in men, and is a primary cause of hypothryroidism, an under-active thyroid gland. However, the key work demonstrating the role of the immune system came later on in the 1950s when researchers looked again an Hashimoto’s thryoiditis and found that a milky deposit or precipitate formed when an extract of human thyroid gland was added to blood from a patient with the illness. These experiments clearly showed that the blood contained antibodies to a constituent of human thyroid tissue and that these antibodies might be responsible for causing the disease.
These findings, and those of Hashimoto in 1912, led directly to a new concept of disease — a process we call autoimmunity. The thyroid was the first part of the body to be recognised as being capable of suffering from an attack by the body’s own immune defences.