Problem 136 - Objective Biology for NEET

Question

Assertion: Immune response of old person becomes weak. Reason: Thymus is degenerated in old individuals.

Step-by-Step Solution

Answer

The assertion is true, and the reason is a correct explanation of the assertion. The thymus does degenerate in old age, leading to fewer mature T cells and a weaker immune response.

Step 1: Understand the Assertion

The assertion states that the immune response of an old person becomes weak. Immunity refers to the body's ability to fight off disease-causing pathogens. As we age, various physiological changes occur, and the assertion posits that one such change is a weakening of the immune response.

Step 2: Understand the Reason

The reason given is that the thymus degenerates in old individuals. The thymus is an organ situated in the chest, where T cells mature. T cells are a type of white blood cell that play a key role in our immune response by attacking infected cells in our body. Therefore, if the thymus does indeed degenerate in old age, it would result in fewer mature T cells and potentially a less robust immune response.

Step 3: Connect the Assertion and Reason

The assertion and reason are logically connected if the degeneration of the thymus in old age can indeed lead to a weakened immune response. Studies confirm that the thymus does degenerate with age, leading to a reduced output of mature T cells. This reduction in T cell output can contribute to the weakening of the immune response in the elderly, making them more susceptible to infections and diseases. Therefore, the assertion and reason given appear to be logically connected.

Key Concepts

Thymus Degeneration

As individuals age, one of the key immune system changes includes the degeneration of the thymus gland. This small but crucial organ is located in the chest, right behind the sternum. It plays a pivotal role during our early years by producing and maturing T cells, which are essential for recognizing and combating pathogens. As we get older, the thymus gradually shrinks and becomes less active, a process known as thymic involution.
This degeneration in function and size results in a reduced production of new T cells in the body, which are vital for maintaining a robust immune surveillance system. Without a steady supply of fresh T cells, the immune system can struggle to respond efficiently to new infections. Thus, thymus degeneration is a fundamental reason for the age-related decline in immune competence.

T Cells

T cells are a subtype of lymphocytes that originate in the bone marrow but mature in the thymus. Once matured, these cells perform a variety of critical roles in managing and directing the immune response. They can be broadly classified into different types based on their functions:

• Helper T Cells: These cells assist in activating other immune cells, augmenting the immune response.
• Cytotoxic T Cells: These cells directly attack and destroy cells that have been infected by viruses or have become cancerous.
• Regulatory T Cells: These cells help in modulating the immune response and maintaining immune tolerance, preventing autoimmune reactions.

As the thymus degenerates with age, the production of these vital T cells declines, thereby weakening the immune system's ability to respond to pathogens. This underscores the connection between thymus health and overall immune effectiveness.

Immune Response

An immune response is the body's method of defending itself against harmful pathogens like viruses and bacteria. It involves a highly coordinated effort between various cells and proteins to identify, attack, and eliminate these invaders. There are two main types of immune responses:

• Innate Immune Response: This is the first line of defense, responding to invaders with non-specific actions. It includes physical barriers, like skin, and immune cells that attack any foreign agent.
• Adaptive Immune Response: This response is more specific and involves the activation of lymphocytes like T cells and B cells that target specific pathogens.

With aging, and due to phenomena like thymus degeneration, the adaptive immune response becomes less efficient. This results in older adults having a weaker ability to fight off infections, making them more prone to diseases. Understanding these changes can help us improve strategies for strengthening elderly immune health.