The immune system can be rejuvenated by eliminating blood stem cells that promote inflammation. Scientists from the United States have demonstrated this in elderly mice, in which they have restored the ability to contain viruses and respond to vaccination.
The treatment consists of antibody therapy that selectively eliminates harmful cells. When this treatment can be applied to people in the future, it can “improve functional immunity to combat infections, chronic diseases and cancer,” the researchers write in the journal Nature, where they present their results today.
“This is a true paradigm shift; “Researchers and doctors should think differently about the immune system and aging,” says Jason Ross, from Stanford University and first author of the research. But he warns, in an email sent to La Vanguardia, that “clinical trials are still years away” in people.
The research is based on the observation that the immune system is divided into two main cell types. On the one hand, those that learn to recognize specific proteins, for example from a virus or tumor cells, and attack them precisely (called lymphocytes). On the other hand, those that protect indiscriminately without recognizing any specific enemy (called myeloid cells, like those that cause fever).
These two types of cells are produced by the same blood stem cells. But – and here is the key to the research – the composition of blood stem cells is not the same in young and old people.
In young people, balanced stem cells predominate, producing lymphocytes and myeloid cells in adequate proportions. As you age, balanced stem cells decrease and one type of unbalanced stem cells increase, producing more myeloid cells and fewer lymphocytes. This process means that, with age, protection against infections and cancer is reduced due to a lack of lymphocytes, and inflammatory health problems and blood cancers increase due to excess myeloid cells.
The experimental treatment to rejuvenate the immune system consists of eliminating unbalanced stem cells. To do this, researchers have designed antibodies capable of recognizing and attacking these cells and have administered them to mice between 18 and 24 months old, which is an advanced age for a mouse.
They have proven that, with the treatment, they achieve an increase in the proportion of balanced stem cells; a reduction of inflammatory molecules; an increase in lymphocyte production; and a rejuvenation of the lymphocytes themselves, which recover the characteristics of the lymphocytes of young mice.
These effects were observed from the first weeks after the treatment, which was administered only once, and have been maintained for months. “We were surprised that a single course of treatment had such a long-lasting effect,” says Jason Ross in a statement from Stanford University.
To make sure that these changes effectively improve the immunity of the mice, the researchers infected them with a murine virus. They have thus shown that the immune response of older mice is more effective if they have previously eliminated unbalanced stem cells.
Along the same lines, when a vaccine is administered to elderly mice, they produce more lymphocytes and are better immunized if the unbalanced cells have been eliminated.
“This discovery changes the way we think about stem cells at every stage of aging,” Irving Weissman, the Stanford University scientist who first isolated stem cells from the blood of mice and people, said in a statement. who has co-directed the current research.
With the aim of translating the treatment to people, researchers have already identified three molecules from unbalanced human stem cells that could be attacked with antibodies. “We think this study represents the first step in applying this strategy in humans,” says Ross.
The research has been co-led by Stanford University and the US National Institute of Allergy and Infectious Diseases.
“Interventions that restore the youthful function of blood stem cells could have an enormous impact on improving immunity, reducing the incidence and severity of chronic inflammatory diseases, and preventing blood diseases” such as hematological cancers, they assess in an article analysis published in Nature by researchers Yasar Arfat Kasu and Robert Signer, from the University of California, San Diego, who were not involved in the research.
