We know that older people have problems with immunity and often get diseases that are usually avoided by younger residents. However, science did not have much knowledge about the mechanisms. Now scientists at the Florida campus of The Scripps Research Institute have conducted a study and demonstrated how aging cripples the production of new immune cells, which decreases the immune system’s response to vaccines and puts the elderly at risk of infection. Furthermore, this study also shows how antioxidants in the diet can slow this damaging process.
This entire research focused on an organ called the thymus, which produces T lymphocytes. They are critical immune cells that must be continuously replenished to respond to new infections. Professor Howard Petrie, one of the authors of the study, explained that “the thymus begins to atrophy rapidly in very early adulthood, simultaneously losing its function”.
He also noted that “this new study shows for the first time a mechanism for the long-suspected connection between normal immune function and antioxidants.” These discoveries are very important, as scientists were trying to come up with new therapies to stop weakening of immune systems of elderly people for quite some time, but it is very hard without the knowledge about the mechanisms behind this process.
In order to research this process, scientists used mouse models. They developed a computational approach for analysing the activity of genes in two major thymic cell types—stromal cells and lymphoid cells. Mouse tissues are actually very similar to human tissues in terms of function and age-related atrophy.
Researchers found that stromal cells were lacking an antioxidant enzyme called catalase, which results in elevated levels of the reactive oxygen by-products of metabolism and, subsequently, accelerated metabolic damage. In other words, this research showed how important this antioxidant is for healthy immune system and how its deficiency can lead to impaired immune system of older people.
In order to make sure that catalase is as important as scientists think, they increased amount of this antioxidant in genetically altered animal models. It resulted in preservation of thymus size for a much longer period. Furthermore, some animals that participated in the experiment were also given two common dietary antioxidants, including vitamin C, and were also protected from the effects of aging on the thymus. These all findings provide new evidence supporting so called the “free-radical theory” of aging.
This theory proposes that reactive oxygen species, for example, hydrogen peroxide, which are produced during normal metabolism, cause cellular damage that contributes to aging and age-related diseases. Other theories explain aging through sex hormones, particularly androgens such as testosterone, but do not answer why the thymus atrophies so much more rapidly than other body tissues.
Although thymus is very responsive to androgens, this new study showed that the mechanism of aging in the thymus is the same as in other body tissues. This does not support theories about correlation of sex hormones and aging. However, this new study showed that aging of the thymus accelerated by a deficiency in the essential protective effects of catalase, which is found at higher levels in virtually all other body tissues.
How significant are these discoveries? Well, aging processes are always very interesting for scientists, because staying young for as long as possible has been a dream of many generations. But these findings are tackling issue of preserving health throughout the life of the people to improve quality of life and make aging a more enjoyable part of life rather than staying young forever.