CD1 a with Urushiol (IMAGE) Monash University Caption Stylised image: Urushiol (in green), the 'active ingredient' in poison ivy, entrapped by CD1a molecule (in pink), which mediates the inflammatory response. Credit Imaging CoE Usage Restrictions None License Licensed content 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.