Factors changing in blood abundance with age, potentially transmitting damage, may include cells like T cells and small molecules like glutathione.

“The big thing that needs to be taken into account here is that the factors that change in their abundance in the blood during age, whether up or down, and that may have an effect in terms of if you like transmitting pathogenic damage from one place in the body to another, those things are, first of all, they're not necessarily just proteins. We also have to worry about cells, the fact that you have changes in the relative abundance of different types of T cells for example. And there's also a small molecule, glutathione, things like that.”