Given below are two statements: one is labelled Assertion(A) and other is labelled Reason(R).

Assertion (A): The immune responses of old persons are weak.

Reason (R): Thymus is degenerated in old individuals resulting in a decreased production of thymosin.

In the light of above statements, choose the correct answer from the options given below.

Both the assertion (A) and the reason (R) are correct, and the reason (R) provides a valid explanation for the assertion (A).

Assertion (A) is true. As people age, their immune responses tend to weaken. The thymus is a primary organ of the immune system that plays a crucial role in the development and maturation of T lymphocytes (T cells), which are important for cell-mediated immunity. Over time, the thymus undergoes a process of involution or degeneration, which means it becomes smaller and less active.

Reason (R) is true. The reason for the weakening of the immune response in old individuals is related to the degeneration of the thymus. With a less functional thymus, there is a decreased production of thymosin, which is a hormone that helps in the maturation and differentiation of T cells. As a result, there are fewer fully functional T cells available to mount an effective immune response. This decline in immune function is one of the reasons why older individuals may be more susceptible to infections and less responsive to vaccines compared to younger individuals.