Micrograph of S. aureus Skin Abscess (image) University of North Carolina Health Care Caption Cell nuclei are stained magenta and polyamine producing macrophages are blue. The host is attempting to wall off the infection by laying down a surrounding layer of collagen (gold) and other matrix proteins. Credit Richardson Lab, UNC School of Medicine Usage Restrictions None 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.