Novel mechanism which extends life of immune system

A new mechanism that slows down and may even prevent the natural ageing of immune cells-one of the nine 'hallmarks of ageing'*-has been identified by an international team led by UCL scientists. Published in Nature Cell Biology, researchers say the discovery in-vitro (cells) and validated in mice was 'unexpected' and believe harnessing the mechanism could extend the life of the immune system, allowing people to live healthier and longer, and would also have clinical utility for diseases such as cancer and dementia.

With the immune system no longer functioning effectively, this leads to the onset of chronic infections, cancerous disease and death. Telomere attrition has been described as one of the 'hallmarks of ageing'*.

In the study, in vitro, researchers initiated an immune response of T-lymphocytes against a microbe (foreign infection). Unexpectedly, they observed a telomere transfer reaction between two types of white blood cells, in 'extracellular vesicles'. An antigen presenting cell (APC), consisting either of B cells, dendritic cells or macrophages, functioned as a 'telomere donor', to the T lymphocyte – the telomere recipient cell. Upon transfer of the telomeres, the recipient T cell became long-lived and possessed memory and stem cell attributes, enabling the T cell to protect a host against a lethal infection in the long term.

The telomere transfer reaction extended certain telomeres about 30 times more than extension exerted by telomerase. Telomerase is the single DNA synthesising enzyme that is devoted to telomere maintenance in stem cells, cells of the immune systems and found in fetal tissue, reproductive cells and sperm. However, it does not provide this function in other cells, leading to telomere attrition. Even in immune cells where the enzyme is naturally active, continuous immune reactions cause progressive telomerase inactivation leading to telomere shortening, when cells stop dividing, and replicative senescence occurs.

On discovering the new 'anti-ageing' mechanism, the same research team established that telomere extracellular vesicles can be purified from the blood, and, when added to T cells, present anti-ageing activities in immune systems from both humans and mice.

Reference:

Dr Alessio Lanna et al,Intercellular telomere transfer rescues T cells from senescence and promotes long-term immunological memory, Nature Cell Biology, DOI: 10.1038/s41556-022-00991-z