A key type of immune cell ‘self-renews’ in humans which could help improve the design of vaccines, a new study suggests.

Scientists said it was an unexpected discovery as it was previously believed that this type of T-cell had reached “end-stage” and would die following one more stint at helping people fight off – or live with – certain infections.

It suggests these cells could play a much bigger part than previously thought in lifetime immune memory and the finding could also have important implications for vaccine design.

The research was carried out by US researchers and scientists at Cardiff University, St George’s, University of London and Imperial College London.

Lead author Dr Kristin Ladell, from Cardiff University, said: “Since the Covid-19 pandemic, T-cells – the immune cells that have a crucial role in killing infected cells and protecting us against infection – have been in the spotlight, and it is crucial we continue to learn more about the role they play in long-term immunity, for good or for bad.

“Here, we have clearly shown that a type of T-cell we thought was senescent – that is, aged and deteriorating in function – is in fact self-renewing in humans.

“The very fact this is happening suggests they have a positive role to play in the long-term maintenance of immunological memory, which is critical for human health.”

Researchers used complex methods to find that CD57+ memory T-cells proliferate and self-renew.

They tracked the cells in young and elderly adult volunteers, with or without HIV-1 infection.

The experimental results were complemented by mathematical modelling performed at Imperial College London which determined that most CD57+ memory T-cells self-renew.

Dr Ladell added: “This finding is important for the understanding of how immunological memory is maintained during the life course and for vaccine design and immunotherapy.

“For example, with Covid-19, the key aim is to create a vaccine that induces a protective, long-lasting immune response that includes T-cells, but to do this, we need to learn more about how these key immune cells work.

“This could help determine whether a new vaccine might prove effective or not.”

– The study is published in the journal Cell Reports.