Placental Tissue (IMAGE) Howard Hughes Medical Institute Caption When human placental tissue (fluorescence microscopy image shown) is exposed to interferon-β, it develops syncytial knots, which appear as protruding bulges, not seen in healthy tissue. Credit Yockey et al., <i>Science Immunology</i> (2018) Usage Restrictions Must use credit 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.