The secret of longevity of blind people
Blind rodents live longer than their fellows due to naivety
Their immunity remains forever young
Researchers from the Institute of Bioorganic Chemistry of the Russian Academy of Sciences, the Volga Research Medical University and other research institutions in Russia, the Czech Republic and Israel compared the repertoire of T-cell receptors of blind mice (Spalax spp.), house mice (Mus musculus) and humans (Homo sapiens). It turned out that the percentage of naive T-cells (T-lymphocytes), due to which the body can cope with those infections that it has not previously encountered, practically does not decrease in blind people, unlike ordinary rodents and humans, up to the very old age. A preprint of the scientific article is published on the bioRxiv website (Izraelson et al., T cell immunity does not age in a long-lived rodent species).
As the body ages, the efficiency of many of its systems, including the immune system, decreases. This is especially clearly seen in the example of acquired immunity, largely provided by T cells. These cells are formed and mature in the thymus gland – thymus. In humans, these processes are active up to about 20 years, in mice – up to 3 months. At an older age in both species, the thymus significantly decreases in size. All T-cells that have had contact with foreign substances and organisms acquire "specialization" – they learn to react quickly to the pathogens of a particular disease. But considering that new T-cells are almost not formed in adulthood, naive T-lymphocytes in a single organism become less and less over time. As a result, the ability to learn to respond quickly to new, previously unknown infections is lost.
Some mammals, such as naked diggers (Heterocephalus) and blind mice (Spalax), are distinguished by a large life span (20-30 years) for their size (weight no more than several hundred grams) and an unusual aging trajectory. For example, compared to humans and many other animals, they are much less prone to malignant tumors in old age. The authors of the new article suggested that in addition to "resistance" to cancer, long-lived rodents may have ageless T cells. Since the state of a T-lymphocyte is determined by the repertoire of T-cell receptors (TCR), it is possible to understand what percentage of T-cells are naive and still able to learn responses to new infections by analyzing the repertoire of TCR lymphocytes of a particular organism. All other things being equal, the diversity of TCR is higher with a large number of naive T cells, since it is not yet known which types of these receptors will be useful in the fight against infections and which will not.
The scientists analyzed the repertoire of T-cell receptors in organisms of two species – blind mice caught and lived from several months to 17.5 years in captivity and C57Bl laboratory mice free of specific pathogens/6. In these animals, the spleen was removed, the T-lymphocytes contained in it were filtered and the genes of various fragments of TKR contained in them were sequenced. Similar results for peripheral T-lymphocytes (taken from capillaries) of human blood were obtained from previous studies.
As earlier studies have shown, the percentage of naive T-cells in mice and humans is getting smaller with age: as they encounter new infections, they accumulate more and more "trained" TKRs on their surface, whose genes differ in structure from the genes of "non-frightened" T-cell receptors. But for blind people, this pattern is not fulfilled. Their share of naive TKR remains the same for most of their lives until old age. With a high degree of probability, due to this, they resist infections equally well at any age, but there is no experimental confirmation of this yet: no one has purposefully infected blind people with various viruses, bacteria or fungi to test their immunity in different years of life. Now we see that such a study would be useful to conduct.
The authors of the work suggest that the exceptional life expectancy for such a small animal as a blind man is largely due to the newly discovered features of his immunity. If this is the case, then the role of age-related changes in the immune system in the general course of aging of the body should be significantly revised.
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