Too Much of a Good Thing (image) Brown University Caption The protein CHI3L1 works to protect injured cells and to repair damage. In lung tissue, damage repair means a buildup of scar tissue, which compromises the lung. Levels of CHI3L1 are higher in patients with idiopathic pulmonary fibrosis (right) than in healthy controls. Credit Brown University/Yale University Usage Restrictions with credit Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.