Final answer:
An immune-related change in the elderly is the decreased production of memory B cells. So, correct option is (D).
Step-by-step explanation:
The immune-related change in the elderly population that is described is D) Decreased memory B cells. As individuals age, a process known as immunosenescence occurs, which is the gradual deterioration of the immune system brought on by natural age advancement.
One of the key features of immunosenescence is the decreased production of new B and T cells due to involution of the thymus, leading to a decline in the overall function of the immune system. Furthermore, the mechanism behind memory B cells is that they are long-lived cells that confer immunity by remembering past infections and responding more quickly to repeated exposures to the same pathogen.
However, with age, the population of these cells diminishes, contributing to a lower ability to fight off infections. This process makes older adults more susceptible to new infections and reduces the efficacy of vaccinations.