Which statement best describes an autoimmune disease?

Which statement best describes an autoimmune disease?

• A. A disease that only affects the immune system's production of antibodies.
• B. A disease in which the body attacks foreign pathogens after infection.
• C. A disease caused by a deficiency in red blood cells.
• D. A disease in which the body attacks its healthy cells.

Answer: (D)

Autoimmune disease happens when the immune system turns against the body's own tissues. Normally the immune system can tell self from non-self and only targets invaders like bacteria or viruses. But in autoimmunity, the system loses that tolerance and attacks healthy cells, causing inflammation and tissue damage in whatever organs are involved. This is why the statement describing the body attacking its healthy cells best captures what an autoimmune disease is. Some other descriptions aren’t the same idea. Merely producing antibodies isn’t the whole story—autoimmune conditions can involve antibodies, but they can also involve immune cells that mistakenly attack self-tissues. Attacking foreign pathogens after infection describes a normal immune response, not autoimmunity. A deficiency in red blood cells points to a specific symptom or condition like anemia, not to the immune system attacking the body's own tissues.

Autoimmune disease happens when the immune system turns against the body's own tissues. Normally the immune system can tell self from non-self and only targets invaders like bacteria or viruses. But in autoimmunity, the system loses that tolerance and attacks healthy cells, causing inflammation and tissue damage in whatever organs are involved. This is why the statement describing the body attacking its healthy cells best captures what an autoimmune disease is.

Some other descriptions aren’t the same idea. Merely producing antibodies isn’t the whole story—autoimmune conditions can involve antibodies, but they can also involve immune cells that mistakenly attack self-tissues. Attacking foreign pathogens after infection describes a normal immune response, not autoimmunity. A deficiency in red blood cells points to a specific symptom or condition like anemia, not to the immune system attacking the body's own tissues.