Immunity without memory
"Short memory" of immunity can increase life expectancy
A study of Middle Eastern blind mice has shown that these rodents live unusually long due to the fact that their immune system does not have a long-term "memory". Thanks to this, it is constantly updated and does not accumulate errors. The scientists' conclusions were published by the scientific journal Nature Aging (Izraelson et al., Distinct organization of adaptive immunity in the long-lived rodent Spalax galili).
"The data we have collected shows that the traditional understanding of how the adaptive immunity of mammals works is not complete. In particular, a large number of factors indicate that the immunity of these long-lived rodents is oriented towards the formation of short, rather than long-term memory. Its absence may protect blind people from the development of inflammation and autoimmune reactions," the researchers write.
Biologists currently assume that the life expectancy of different animal species is interrelated with their typical body weight. For example, mice, rats or small birds live relatively short, while eagles, elephants and large cats live for tens or even hundreds of years. Sometimes this pattern is violated, as exemplified by the famous "immortal" Cape diggers, whose mass does not exceed 40 grams, as well as people.
Another interesting example of this is three species of Middle Eastern blind mice, large rodents living in Israel and Palestine.
These include the blindfolds of the Golan Heights (Spalax golani), the blindfolds of the Judean Mountains (Spalax judaei) and the blindfolds of the upper Galilee Mountains (Spalax galili). All these rodents are not only long–lived - they live for about two decades, but also highly resistant to cancerous tumors of various types.
A group of Russian and foreign biologists led by Dmitry Chudakov, head of the Department of the Institute of Bioorganic Chemistry of the Russian Academy of Sciences in Moscow, tried to uncover the causes of cancer resistance and longevity of the blind of the Upper Galilee Mountains (Spalax galili) by studying in detail the structure of their immune system.
To do this, scientists tracked how the number, diversity and behavior of immune cells of different types involved in the production of antibodies and the recognition of pathogens, as well as the activity of genes that control their vital activity, are changing. Biologists compared this information with how similar parts of the immunity of humans and mice of the same age work.
These observations revealed a lot of oddities in the work of immunity of both elderly and young diggers, which made scientists doubt that our current ideas about the work of acquired immunity correspond to reality.
In particular, Chudakov and his colleagues found that there were very few "adult" T-cells and B-cells in the body of blind people responsible for maintaining long-term immunity and the production of antibodies to already familiar pathogens. In addition to this, the diversity and number of "blanks" of these immune cells in their body did not fall with age, but remained constantly high.
Both are completely out of character for other mammals that develop long-term immunity and gradually lose most of the "blanks" of T cells and B cells as they get old. Similarly, the body of blind mice did not produce a number of signaling molecules that usually control the maturation of these bodies and their transformation into cells capable of producing antibodies and killing infected cells.
Such a feature of the immunity of these long-lived rodents, according to Chudakov and his colleagues, can protect them from the formation of a large number of immune cells, during the maturation of which errors occurred, as a result of which they begin to attack the cells of the body itself or cause chronic inflammation. Both often cause the development of cancer and mass cell death in various organs, including the brain.
This useful feature of their immunity is not given to rodents for free – the lack of "long-term" memory makes them more vulnerable to attacks by microbes and viruses, forcing them to go through the entire cycle of antibody formation and infection suppression virtually every time. It takes a lot of time and energy, even if the rodent's life is not in danger.
How exactly the immunity of blind people replenishes the stocks of "blanks" of T-cells and B-cells, scientists cannot yet say for sure. The researchers hope that subsequent experiments will help them find the answer to this question and will allow them to understand how much this feature of immunity affects the longevity of rodents.
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