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

• A. Cirrhosis
• B. Diabetes
• C. Hypertension
• D. Immunodeficiency

Answer: (D)

Understanding how the immune system works helps you see what a disorder in that system looks like. The immune system defends the body against pathogens using cells, antibodies, and other defenses. When this system doesn’t function properly, the body can’t fight infections effectively, which is what an immune system disorder means. Immunodeficiency is exactly that—it’s a condition in which the immune response is weakened or absent, making someone more prone to infections. The other conditions involve different parts of the body: cirrhosis is liver damage, diabetes is trouble regulating blood sugar, and hypertension is high blood pressure. They’re health issues, but not immune system disorders.