What is an effect of aging on the immune system?

Aging has several significant effects on the immune system, one of which is an increased susceptibility to infections. As individuals age, their immune system undergoes various changes that contribute to a decline in immune function, known as immunosenescence. This includes a decrease in the production of new immune cells, alterations in the function of existing immune cells, and a reduced ability to respond to pathogens and vaccines.

Older adults often have a diminished response when exposed to new antigens, which increases their vulnerability to infections like influenza, pneumonia, and other infectious diseases. Additionally, the number of naive T-cells decreases while memory T-cells may remain stable, leading to an impaired ability to respond to new infections. All of these factors collectively explain why aging is associated with a higher likelihood of infections rather than enhanced immune responses or a stabilization of immune functions.

In contrast, the other answer choices fail to capture the broader realities of aging and immune function dynamics: aging does not enhance immune responses, it does not decrease the likelihood of autoimmune diseases (in fact, older individuals may still experience them), and rather than stabilizing immune functions, aging leads to increased variability and compromised responses within the immune system.