Loss of self-tolerance results in

• A. Autoimmune disease
• B. Graft-versus-host disease
• C. Immunodeficiency
• D. Tumors

Answer: (A)

Self-tolerance is the immune system’s ability to recognize its own tissues and not attack them. When this tolerance is lost, autoreactive immune cells or autoantibodies target the body’s own components, leading to autoimmune disease with inflammation and tissue damage. Graft-versus-host disease happens when donor immune cells attack the recipient after a transplant, not due to the body's own tolerance failing. Immunodeficiency is a reduced ability to mount immune responses, not an autoimmune attack. Tumors involve complex interactions with the immune system, including evasion, but they’re not the direct result of losing self-tolerance. Thus, loss of self-tolerance most directly results in autoimmune disease.