As people age, immune cells called T cells tend to decline both in quantity and in quality. Credit: National Institutes of Health, NIAID/Science Photo Library
A twice-weekly cocktail of three messenger RNAs can rejuvenate the weary immune systems of aged mice and boost responses to vaccination and cancer treatments, a study has found1.
The treatment provides a needed boost to immune cells called T cells, which coordinate immune responses and kill infected cells. As people age, their ability to produce T cells wanes, and the ones they have become less effective.
T-cell ageing helps to explain why vaccines are sometimes less effective in older people than in young adults, and why cancer treatments that unleash the immune system against tumours don’t work as well in older adults, says María Mittelbrunn, an immunologist at the Spanish National Research Council in Madrid. Flagging T-cell immunity is also linked to the chronic inflammation associated with many age-related diseases, including some forms of cardiovascular disease.
How to make an old immune system young again “T cells, in particular, are one of the cell types that change the most during ageing,” says Mittelbrunn, who was not involved in the study. “To rejuvenate them could have immense consequences.”
The work was reported in Nature on 17 December and earlier this month at the American Society of Hematology annual meeting in Orlando, Florida.
Targeting T cells
T cells are produced in the bone marrow and then travel to a tiny gland called the thymus to mature. In the thymus, they learn to recognize and respond to pathogens such as bacteria or viruses. They also learn not to attack the body’s own healthy cells.
But the thymus degrades with age: it begins to shrink and is gradually replaced by fatty tissue. Attempts to reverse this using hormone treatments or other drugs have not worked, says Mirco Friedrich, a haematologist and oncologist at the German Cancer Research Center in Heidelberg, and first author of the study.
So, Friedrich and his colleagues decided to take a different approach: rather than directly treating the thymus, they targeted T cells by delivering an experimental therapy to the liver. “Most T cells are in the blood,” Friedrich says. “And the liver receives the body’s whole blood volume.”