Aristocratic spleen
Naked diggers: the "nobility" immune system works better
Naked diggers – small underground inhabitants with amazing longevity and resistance to diseases – are one of the favorite objects of study for biologists and physicians. Now researchers have discovered an intriguing connection between the work of the immune system of individuals and their social status in "society".
The widely known naked diggers (Heterocephalus glaber) are African rodents that live surprisingly long, despite their small size, do not get cancer, almost do not feel pain and tolerate low oxygen content in the air well.
These animals also differ in a rather non-standard way of life and the structure of communities. Naked diggers justify their name, as they live underground, where they build a complex system of moves. They live in colonies of about 40-70 individuals, each of which has its own rank and its own range of responsibilities. It is headed by a "queen" – the only breeding female, several "close" males are the fathers of her offspring, and the rest of the community members are just workers, each busy with their own business.
When studying the laboratory population of naked diggers, scientists from Germany and South Africa discovered a curious fact: some individuals have a noticeably larger spleen – an organ that not only serves as a blood depot, but also performs important hematopoietic and immune functions.
The article by Bégay et al. Immune competence and spleen size scale with colony status in the naked mole-rat is published in the journal Open Biology.
First of all, scientists ruled out the possibility that animals with such a spleen were simply sick. Then it turned out that the spleen of such individuals has an increased number of macrophages – immune cells that literally "swallow" pathogens. Changes in the activity of a number of genes were also detected in the spleen, which indicated an "increased combat readiness" of the immune system. In other words, the immune system of such individuals would react more effectively to the penetration of an infectious agent or the appearance of cancer cells.
As a result, it turned out that the size of the spleen of an individual is closely related to its social status. The ranks of the studied animals were set in pairs of squats, where naked diggers were forced to run towards each other in a narrow tube. In this test, an individual with a higher rank does not miss his counterpart and continues to move forward.
A total of 24 healthy individuals of naked diggers were tested. At the same time, it turned out that three-quarters of animals with a small spleen had the lowest rank, and individuals with a large spleen almost all belonged to the "nobility".
It should be noted that this phenomenon – the relationship between the effectiveness of the immune system of individuals and their social rank – is known not only for naked diggers. In particular, a similar pattern is observed in macaques, although in this case other elements of immune protection change in animals. And although the higher efficiency of the immune system gives high–ranking individuals an advantage, the question still remains: what is primary - status or strong immunity?
Naked diggers acquire their social status during their lifetime. At the same time, scientists suggest that the driving force of moving up the hierarchical ladder may be the desire for mating. And if the most "successful", i.e. reproducing, males also have more effective immune protection, then this serves as a guarantee that the genes that determine the best work of immunity will be transferred to the offspring. So in the case of naked diggers, according to researchers, it may be the social rank that is primary.
In addition, it is known that successful individuals of this species live longer: for example, the "queen" rarely dies of old age, usually she is killed during a "palace coup". So it is social success that can stimulate the immune system to ensure a long and fruitful life.
It is worth recalling here that reproduction and maintenance of immunity are two "mutually exclusive" strategies, since both of them require high energy expenditure. On the other hand, the workers of naked diggers are mainly engaged in heavy, energy-consuming work, primarily digging underground tunnels, and in this respect the dominant males are clearly in a privileged position.
As for humans, it is unlikely to draw any parallels here, however, researchers plan to study the role of the spleen in the work of anti-cancer mechanisms of naked diggers, which will expand our data on the functions of this organ.
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