The activation of bystander CD8+ T cells and their roles in viral infection

Viral infection: Inciting an immunological mob Immune cells that are non-specifically activated during infection can offer protection, but may also inflict collateral damage on infected patients. T cells normally mount an antigen-specific immune response, but certain T cells can become stimulated during viral infection without selective activation by a particular antigen. Tae-Shin Kim and Eui-Cheol Shin at KAIST in Daejon, South Korea, have reviewed current insights into this ‘bystander activation’ phenomenon. They explore how the immune response to viruses such as influenza and hepatitis A produces molecular signals that induce bystander activation of ‘killer’ T cells. In some scenarios, this leads to stronger immune protection, but these cells can also damage host tissues, or contribute to disease progression. Modulating this nonspecific response could prove valuable in managing the severity of viral disease.