Diagram of Macrophage Interaction (image) University of Pennsylvania Caption Macrophages are immune cell 'border guards' that have evolved to eat all sorts of foreign microbes, but they also eat many particles that are intended for therapeutics and imaging. A 'Minimal peptide "Passport"' attached to the particles provides recognition signals so that the particles are not eaten, thus improving delivery to diseased cells in the body. Credit Mary Leonard, Biomedical Art & Design, University of Pennsylvania 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.