aPD1 (image) Johns Hopkins Medicine Share Print E-Mail Caption When the tumor protein PD-L1 (blue) engages with PD-1 (purple), it damps the response of killer T cells (pink). Molecules that engage PD-1, called antibodies (yellow), can prevent this interaction from taking place. Credit Alyssa Kosmides and Randall Meyer, Johns Hopkins Medicine Usage Restrictions None Share Print E-Mail 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.