Question: How far has your research been able to understand the process of how a virus can "age" the cells of the immune system?

Carolyn Nielsen answered on 10 Nov 2015:

There are lots of people working on this puzzle of how cytomegalovirus affects the immune system, and my research is a piece of this.

What I have seen is that, in healthy adults, a type of white blood cell called natural killer cells don’t respond as well to vaccines in people infected with cytomegalovirus, as compared to people who aren’t infected.

The main theory at the moment is that interaction of natural killer cells with cytomegalovirus causes an expansion of a more mature type of natural killer cells. (We don’t know exactly how this happens though!) These cells are less responsive to signals by molecules called cytokines, which act as messengers between cells and can tell natural killer cells to activate. So if you have more of these mature natural killer cells, you won’t respond as well to cytokine signals overall. These signals are important in a lot of contexts, including during infection or after vaccination.

This is very similar to ageing, because as you get older you accumulate these more mature natural killer cells as well. What’s really interesting is that young people with cytomegalovirus can have natural killer cells that look more like what you would find in old people!