Which statement correctly defines an autoimmune disease?

Which statement correctly defines an autoimmune disease?

• A. A disease caused by a bacterial infection
• B. A disease in which the immune system attacks the body's own cells
• C. A disease caused by vitamin deficiency
• D. A disease transmitted by a parasite

Answer: (B)

Autoimmune disease happens when the immune system mistakenly turns against the body's own cells. Normally the immune system recognizes what belongs to you and what doesn’t, mounting defenses against invaders while leaving your own tissues alone. When self-tolerance breaks down, the immune system targets your own tissues, causing inflammation and damage in specific organs or throughout the body. That idea is what this statement captures: the immune system attacking the body's own cells defines an autoimmune condition. This isn’t about bacteria, vitamin shortfalls, or parasites—those involve infections or nutritional issues, not an immune attack on self. Examples include type 1 diabetes, where pancreatic cells are attacked, or rheumatoid arthritis, where joints are affected, illustrating how the immune response can mistakenly harm the body it’s meant to protect.

Autoimmune disease happens when the immune system mistakenly turns against the body's own cells. Normally the immune system recognizes what belongs to you and what doesn’t, mounting defenses against invaders while leaving your own tissues alone. When self-tolerance breaks down, the immune system targets your own tissues, causing inflammation and damage in specific organs or throughout the body. That idea is what this statement captures: the immune system attacking the body's own cells defines an autoimmune condition. This isn’t about bacteria, vitamin shortfalls, or parasites—those involve infections or nutritional issues, not an immune attack on self. Examples include type 1 diabetes, where pancreatic cells are attacked, or rheumatoid arthritis, where joints are affected, illustrating how the immune response can mistakenly harm the body it’s meant to protect.