Which immune-related change is observed in the elderly population?

The correct choice highlights a common phenomenon in the aging immune system, specifically the behavior of memory T cells. As individuals age, the generation of new naive T cells decreases, and there is a notable expansion of certain subsets of memory T cells. This occurs because older adults tend to have been exposed to a wider array of pathogens over their lifetime, leading to an accumulation of memory T cells that can quickly respond to previously encountered infections.

This increase in memory T cells is critical as it reflects the body's ability to recall and respond to past infections, which is beneficial for the immune response. However, although many aspects of the immune response decline with age—such as the production of new naive T cells—the persistence and enhancement of memory T cells play a protective role, potentially allowing for a more effective response to infections that have been previously encountered.

The other changes associated with aging might involve other aspects of the immune response, such as the production of antibodies or the activity of different immune cells, but the established fact regarding memory T cells specifically points to their increased presence in the elderly population. This nuanced understanding of the immune landscape in older adults is essential for anticipating how to approach immune-related health issues in this demographic.