When the body is exposed to new infection for the first time, it makes memory T cells that may remain there for years.
If there is another exposure to the same infection, the T cells recognise it and instruct the body to make antibodies.
Building up antibodies is the basis of vaccination and the way we fight off infective processes.
Dr Terry Gaymes, senior lecturer of immunology at Kingston University, tells us something important we don’t know about memory T cells.