Trojan Cell (IMAGE) Washington University School of Medicine Caption Immune cells in the spleen have brought in stowaways: Listeria bacteria, which appear green in the image. Researchers at Washington University School of Medicine in St. Louis have found that the immune cells the bacteria have exploited can be both helpful and harmful in fighting infection. The cells could be particularly useful in efforts to turn the immune system against cancers using vaccines. Credit Kenneth Murphy 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.