Researchers from the Florida campus of The Scripps Research Institute (TSRI) have demonstrated how aging diminishes the production of new immune cells, crippling its ability to respond to vaccines and thus increasing the risk of disease and infection in the elderly. The study also shows how dietary antioxidants could curb this process.
The Study: Using The Thymus To Study Immune Crippling In The Elderly
The study, published in the journal Cell Reports, focused on the thymus – an organ that produces T lymphocytes (immune cells requiring continuous renewal to fight infections). TSRI Professor Howard Petrie explained that the thymus begins to degenerate rapidly during early adulthood, consequently losing its function. “This study demonstrates, for the first time, a mechanism for the long-suspected connection between normal immune function and antioxidants”.
Dr Petrie and colleagues used a computational approach to study the activity of genes in two vital cell types of the thymus – the stromal cells and lymphoid cells. Researchers used a mouse-model, since their age-related atrophy and loss of function of the thymus were very similar to that in humans. The team observed that stromal cells were highly deficient in the antioxidant enzyme catalase. This resulted in increased levels of reactive oxygen by-products which amplified metabolic damage.
To confirm the significant role of catalase, scientists elevated its levels in genetically altered animal models. This resulted in maintenance of thymus size for a prolonged period. Moreover, animals that were administered with two ordinary dietary antioxidants, such as vitamin C, also remained protected from age-related thymus deterioration.
Aging And Antioxidants: Two Opposites Of Immune System
Overall, the findings provide evidence to support the ‘free-radical theory’ of aging, according to which elevated levels of reactive oxygen species (ROS), such as hydrogen peroxide, cause cellular damage leading to aging and age-related diseases.
Other studies have demonstrated that sex hormones – particularly androgens – play a significant role in the process of aging. However, they do not provide an answer to the most important question: why does thymus deteriorate at a much higher rate than other body organs and tissues?
“There’s no doubt that the thymus is extremely receptive to androgens”, Dr Petrie stated, “but our study demonstrates that the primary mechanism of aging in the thymus – accumulated metabolic damage – is the same as in other body tissues. However, the process is accelerated in the thymus due to the deficiency of the protective effects of catalase, which is present in higher levels in almost all other tissues of the body”.