Macrophages (IMAGE) European Molecular Biology Laboratory Caption Fluorescence microscopy picture of bone marrow-derived macrophages: red: macrophage marker/ blue: DNA /green: ferritin. Compared to the few control cells present in this picture, IRP-null macrophages express abnormally high levels of ferritin (green), which constitutes a pool of iron Salmonella can exploit. Credit Bruno Galy/DKFZ 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.