The thymus (thymus gland) is an organ of internal secretion, a “factory” for the production of T-lymphocytes– cells that regulate the body’s immune response. Over time, the thymus undergoes involution (reverse development), which is one of the stages of aging. But even if the thymus is fully functional, it would be impossible to transport lymphocytes to their destination without the lymphatic system. In fact, the immune system consists of immune cells (including T-lymphocytes) and lymphoid organs (such as the thymus, spleen, and lymph nodes) circulating throughout the body. When an infection site occurs, immune cells concentrate in the lymph node closest to it, forming the body’s immune response, one of the stages of which is cell proliferation (division). Clinically, this is manifested in an increase and soreness of the lymph node, an increase in body temperature. However, after reaching a certain age, the intensity of the body’s reaction decreases, and the lymph nodes practically do not change during infectious inflammation in the body. This is due to the fact that elderly people experience aging processes inside the lymph nodes: connective tissue grows chaotically and thickens. This makes it difficult for immune cells to move inside the lymph node, which ultimately leads to a decrease in the quality of the immune response of the entire body. That is why, according to the author of the theory, there is no formation of stable long-term immunity, even with the “rejuvenation” of the thymus and an increase in the number of T-lymphocytes by blocking endogenous androgens. Currently, research is underway to study the state of the immune system not only with the full functioning of the thymus, but also with the preservation of lymph nodes, as well as to assess the impact of all of the above on the quality and duration of life. Despite the increase in average life expectancy, most people have been living for the last 15-20 years suffering from various chronic diseases. Perhaps the research results of Nikolic-Zugic’s group and other biogerontologists can give people the opportunity to maintain their health and lead an active lifestyle until the last days.