An iron-regulating molecule called hepcidin is produced by the immune system and restricts the growth of gut bacteria after an intestinal injury, helping to heal the lining of the intestine, according to a study by Weill Cornell Medicine, NewYork-Presbyterian and Institut Cochin investigators. The study, published April 10 in Science, was conducted in mice and human samples and could have important implications for treating gastrointestinal diseases that damage the lining of the intestines.