Which of the following is a major disorder of the immune system?

• A. Hypersensitivity
• B. Congenital Deficiency
• C. Acquired Immune Deficiency
• D. Autoimmune Disease

Answer: (A)

Hypersensitivity describes exaggerated or inappropriate immune responses to harmless substances, which makes it a major category of immune system disorders. The immune system normally targets real threats while sparing the body, but in hypersensitivity this regulation goes awry, leading to allergic conditions such as hay fever, food allergies, asthma, and even potentially life-threatening reactions like anaphylaxis. This concept stands apart from immunodeficiency disorders, where the immune system is weakened and fails to mount an adequate defense against infections (whether congenital or acquired), and from autoimmune diseases, where the immune system attacks the body's own tissues. Understanding hypersensitivity helps explain why certain exposures trigger damaging immune reactions even when there’s no real pathogen present.