Which immune function is decreased with aging?

The correct answer pertains to the decline of adaptive immune stimulation with aging. As individuals grow older, the immune system experiences a general decline in its ability to mount effective responses to new pathogens and vaccines, which is primarily due to changes in T cell function and the reduced production of new T cells by the thymus. This decline leads to a less robust adaptive immune response, making it more challenging for older adults to defend against infections or respond adequately to vaccinations.

In contrast, while memory T cells and memory B cells can also show changes with age, they do not necessarily decrease in function or quantity to the same extent as the overall adaptive immune stimulation. In fact, some studies suggest that memory B cells may even persist for longer periods, providing a degree of immunity from previous infections. Macrophage activity can also be affected with aging, but this typically focuses more on innate immunity rather than the specific adaptive responses that are crucial for long-term immunity. Thus, the decline in adaptive immune stimulation most accurately reflects the age-related immune changes.