Why Ageing and Inflammation Affect COVID-19 T-Cell Responses

You're fighting off a new infection like COVID-19. Your T-cells, the immune system's special forces, play a crucial role. But why do some people's T-cells respond better than others? Age and inflammation have a lot to do with it, especially when it comes to severe COVID-19 cases. Scientists looked into this, focusing on patients infected during the first wave in France and Japan. They found that as we get older, our naive lymphocytes—the T-cells that haven't encountered an infection before—decrease. This age-related change, combined with high levels of systemic inflammation in severe COVID-19 cases, makes it tough for T-cells to fight the virus effectively.In particular, the CD8+ T-cells, which specifically target and kill infected cells, struggle. The proinflammatory cytokine IL-18, which is high in severe COVID-19 cases, hinders the ability of CD8+ T-cells to both start their fight and remember how to fight in the future. Interestingly, this didn't affect the humoral immune responses, which target the SARS-CoV-2 spike protein. These findings could explain why older adults are more vulnerable to infections that cause a strong inflammatory response, like COVID-19.