What is the primary mechanism responsible for pathology in systemic lupus erythematosus?

• A. Allergic reaction to foreign molecules
• B. Antibodies directed against self antigens
• C. Polyclonal activation of cytotoxic T cells
• D. Lack of intracellular killing after neutrophil phagocytosis of bacteria

Answer: (B)

Autoantibody production against self-antigens drives the pathology of systemic lupus erythematosus. These antibodies target nuclear components and other self-mates, form circulating immune complexes, and deposit in tissues such as the kidneys, skin, and joints. The immune complexes activate complement and recruit inflammatory cells, leading to inflammation and organ damage characteristic of lupus—a type III hypersensitivity process. While T-cell involvement occurs, the central feature is autoantibody–mediated immune complex injury. The other options describe mechanisms not responsible for lupus pathology.