T Memory Cells (IMAGE) University of Pennsylvania School of Medicine Caption This image shows the expansion and formation of T memory cells over time after infection or vaccination. Credit The lab of John Wherry, PhD, Perelman School of Medicine, University of Pennsylvania 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.