1. Involution: The thymus undergoes a process called involution, which refers to the gradual shrinkage and reduction of its size and cellularity. This process begins in early adulthood (around 20-30 years of age) and continues throughout life.
2. T Cell Production: The thymus produces new T cells through a process called thymopoiesis. Thymopoiesis involves the differentiation, selection, and maturation of T cells from progenitor cells. As the thymus involutes, the production of T cells decreases.
3. Loss of T Cell Diversity: The thymus plays a crucial role in generating a diverse repertoire of T cells with different specificities. This diversity is essential for the immune system to recognize and respond to a wide range of pathogens. With the decline in thymic function, the diversity of T cells decreases, which can affect the overall immune response.
4. Increased Susceptibility to Infections: As the thymus involutes and the production of new T cells decreases, individuals may become more susceptible to infections. This is because the immune system is less able to recognize and mount effective responses against novel pathogens.
5. Autoimmunity: Age-related changes in the thymus can also contribute to the development of autoimmune disorders. The thymus plays a role in eliminating self-reactive T cells that could potentially attack the body's own tissues. With the decline in thymic function, these self-reactive T cells may escape immune surveillance, leading to the development of autoimmune diseases.
It's important to note that the age-related changes in the thymus are a natural part of the aging process. While they can affect immune function, most individuals maintain a robust and functional immune system throughout their lives. However, certain conditions, such as severe stress, malnutrition, or certain medical treatments, can accelerate thymic involution and further compromise immune function.