Pembrolizumab Image (IMAGE) Fred Hutchinson Cancer Center Caption Multispectral immunofluorescence shows the interface between Merkel cell tumor cells (orange) and host immune cells (yellow marks CD8+ lymphocytes, red marks CD68+ macrophages). Cell-surface PD-L1 expression (green) is observed on macrophages, lymphocytes and tumor cells, adjacent to PD-1 expression (white) on lymphocytes. Credit Courtesy of Janis Taube, Johns Hopkins. 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.