Small Blood Vessels (IMAGE) Heidelberg University Hospital Caption In the cell walls of small blood vessels -- here stained blue -- proteins are mediators of anaphylactic shock. Credit Photo: Heidelberg University Hospital. 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.