AIIMS 2003 Zoology Immune System Assertion Reason Question

To analyze the given question, we need to evaluate the Assertion and the Reason, and determine the relationship between them.

Assertion: Mast cells in the human body release excessive amounts of inflammatory chemicals which cause allergic reactions.

Reason: Allergens in the environment, upon reaching the human body, stimulate mast cells in certain individuals.

Explanation:

1. Understanding the Assertion:

   • Mast cells are a type of white blood cell that play a crucial role in the immune system. They are primarily involved in allergic reactions and inflammation. When an allergen (a substance that can cause an allergy) enters the body, mast cells can become activated and release various chemicals, including histamines, cytokines, and other inflammatory mediators. This release can lead to symptoms associated with allergic reactions, such as itching, redness, swelling, and even anaphylaxis in severe cases. Thus, the assertion is true.

2. Understanding the Reason:

   • Allergens, such as pollen, dust mites, or certain foods, can trigger an immune response. In susceptible individuals, the exposure to these allergens leads to the activation of mast cells, which then release inflammatory chemicals. This mechanism explains why some people experience allergic reactions while others do not. Therefore, the reason is also true.

3. Evaluating the Relationship:

   • The reason provides a direct explanation for the assertion. It explains how allergens stimulate mast cells, leading to the release of inflammatory chemicals responsible for allergic reactions. Since both statements are true and the reason correctly explains the assertion, the correct answer is A.

Why Other Options are Incorrect:

• Option B: This option states that both the assertion and reason are true but the reason is not the correct explanation. This is incorrect because, as established, the reason indeed explains the assertion.
• Option C: This option claims that the assertion is true but the reason is false. This is incorrect because both statements are true.
• Option D: This option suggests that both statements are false. This is incorrect as both the assertion and reason have been confirmed to be true.

Conclusion:

The answer is A because both the assertion and reason are true, with the reason providing the correct explanation for the assertion. Understanding the role of mast cells in the immune response to allergens is crucial in appreciating how allergic reactions occur.