Periscope Up! (IMAGE) University of Pennsylvania School of Medicine Caption The thoracic duct carries Tfh-enriched lymphocytes to the blood, including a population of Tfh CXCR5 PD-1markers. Credit Laura Vella, John Wherry, Penn Medicine, JCI 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.