Friend Virus Budding from T-cell (image) University of Utah Caption This electron microscope image shows yellow particles of a mouse leukemia virus named Friend virus emerging or "budding" out of an infected white blood cell known as a T-cell. By allowing the Friend virus to mutate and evolve in mice, University of Utah researchers produced new evidence that an arms race between microbes and immune-system MHC genes is responsible for maintaining an amazing diversity of those genes, even though some of them are responsible for autoimmune and infectious diseases that make us sick. Credit Elizabeth Fischer and Kim Hasenkrug, NIH. Usage Restrictions Credit required 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.