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With advancing age, the total number of T lymphocytes can significantly decrease. However, even in the absence of significant changes in their levels, the risk of contracting infections or developing diseases typically associated with aging (such as tumors) increases due to the reduction in the space available for new immune cells. In fact, senescent T lymphocytes, more resistant to cell death, tend to accumulate, while the production of new T lymphocytes and their ability to differentiate into mature cells decreases.
Both T lymphocyte populations – helper T cells (CD4 +) and cytotoxic T lymphocytes (CD8 +) – can decrease. However, of particular concern is the inversion of the CD4 + / CD8 + ratio, a characteristic of a condition typically associated with aging – the so-called immune risk phenotype (IRP) – considered an indicator of an increased health risk. Indeed, high percentages of CD8 + T cells, combined with low levels of CD4 + T cells and poor proliferation of T cells in peripheral blood, are associated with a significant increase in mortality in the elderly population.
The CD4 + / CD8 + ratio can also be altered by viral infections, including Cytomegalovirus (CMV) infections. In fact, being positive for CMV is one of the most important causes of aging of the immune system. The virus, which remains in the body for life after the first infection, chronically stimulates CD8 + T lymphocytes, promoting their increase. As a result, CD4 + T lymphocytes decrease. Although a large part of the adult population is positive for CMV, few are aware of it. Analysis of the CD4 + / CD8 + ratio can provide significant information on the state of the immune system, revealing unsuspected compromises.

Levels of B lymphocytes vary significantly throughout life. Immediately after birth, their total number doubles, and then remain stable until the age of 2, when it begins to gradually decrease to the typical values of adulthood. From this moment their levels stabilize until, with aging, the production of B lymphocytes in the bone marrow decreases significantly. In particular, chronic inflammation associated with aging can inhibit the production of new B lymphocytes.

The reduction in NK cell cytotoxicity is associated with an increase in morbidity and mortality. Conversely, an active NK cell population is associated with longevity and good health.

Aging is characterized by an increase in NK cells in the blood, but from the age of 50 their production decreases; this suggests that the elderly population is characterized by a higher percentage of “aged” NK cells. CD56bright NK cells, corresponding to the less mature form, decrease; this causes a compensatory increase in the production of molecules involved in inflammation. At the same time, there is an increase in CD56-CD16+ NK cells, in turn characterized by an altered production of the molecules that control inflammation.

The reduction in NK cell cytotoxicity is associated with an increase in morbidity and mortality. Conversely, an active NK cell population is associated with longevity and good health.

Aging is characterized by an increase in NK cells in the blood, but from the age of 50 their production decreases; this suggests that the elderly population is characterized by a higher percentage of “aged” NK cells. CD56bright NK cells, corresponding to the less mature form, decrease; this causes a compensatory increase in the production of molecules involved in inflammation. At the same time, there is an increase in CD56-CD16+ NK cells, in turn characterized by an altered production of the molecules that control inflammation.

In healthy people, about 95% of monocytes are represented by the “classic” form, characterized by a high expression of the CD14 marker and the absence of the expression of the CD16 marker (CD14++ CD16-). From the age of 50, however, the subpopulation of “non-classical” CD14+ CD16+ monocytes begin to increase. At the same time, however, their functionality decreases, while their ability to produce proinflammatory molecules increases.

After the age of 60, the reduction of classical monocytes is significant. At more advanced age, non-classical monocytes also decrease, while another subpopulation of CD16+ cells increases, the “intermediate” CD14 ++ CD16+ monocytes. The increase in CD16+ monocyte subpopulations (non-classical and intermediate) correlates with the development of diseases associated with chronic inflammation (such as cardiovascular disease, obesity, diabetes, arthritis and inflammatory bowel diseases). However, this increase can be effectively countered. In the case of obesity, for example, both dietary intervention and bariatric surgery make it possible to reduce the levels of CD16+ monocytes.

Vitamin D deficiencies are associated with increased susceptibility to infections and the prevalence of autoimmune diseases. Conversely, avoiding them promotes a better functioning of the immune system.
Unfortunately, the low availability of food-borne vitamin D, combined with poor production following exposure to sunlight, means that up to 40% of the adult population may find themselves struggling with a deficiency. Aging further increases this risk, bringing with it others: fractures, infections, cardiovascular diseases, diabetic retinopathy, migraines, tumors and frailty.
Supplements is an effective strategy to correct these deficiencies and promote the proper functioning of the immune system. The daily intake of vitamin D, for example, has been associated with protection from acute respiratory infections