Shadow proteins in thymus may explain how immune system gets to know its own body

Researchers recently identified a protein that appears to work by turning on in the thymus, which lies beneath the breast bone, the production of a wide array of proteins from the body’s periphery. The discovery of the protein called “aire” could shed light not only on how the healthy immune system develops tolerance to its own proteins but also how tolerance is lost, as it is in diabetes, rheumatoid arthritis, Crohn’s disease and other autoimmune illnesses. “Our findings lead back to humans because they tell us about a very important mechanism for controlling autoimmunity,” said Diane Mathis, a Harvard Medical School professor of medicine at Joslin Diabetes Center. “At the same time, they may help us understand why people develop autoimmune diseases.” The findings were reported in the Oct. 11, 2002, issue of the journal Science.