Which statement describes autoimmune disorders?

• A. They occur when the body attacks foreign substances from outside.
• B. They occur when the body perceives part of its own body as foreign and develops self-antigens to that part in order to destroy it.
• C. They are always caused by bacterial infections.
• D. They always resolve without treatment.

Answer: (B)

Autoimmune disorders arise when the immune system loses its ability to distinguish self from non-self and begins attacking the body's own tissues. In this situation, self-antigens on a part of the body are recognized as foreign, triggering an immune response that can involve autoantibodies or autoreactive T cells and lead to inflammation and tissue damage. This is different from responses to outside invaders or allergens, and while infections can sometimes trigger autoimmunity, they are not the defining cause. Autoimmune diseases can be chronic and often require treatment to control the immune attack, rather than resolving on their own.