What hypersensitivity type is responsible for the immune-mediated damage seen in systemic lupus erythematosus?

• A. Type I
• B. Type II
• C. Type III
• D. Type IV

Answer: (C)

The immune-mediated damage observed in systemic lupus erythematosus (SLE) is primarily due to Type III hypersensitivity reactions. In this context, Type III hypersensitivity involves the formation of immune complexes, which are aggregates of antigen and antibody. These immune complexes can deposit in various tissues throughout the body, including the kidneys, skin, joints, and blood vessels.

In SLE, the presence of autoantibodies, such as anti-nuclear antibodies (ANAs) and anti-double-stranded DNA antibodies, leads to the formation of these immune complexes. When these complexes deposit in tissues, they trigger an inflammatory response, attracting leukocytes and activating complement pathways. This results in tissue damage and manifests as the diverse clinical features of the disease, including renal inflammation (lupus nephritis), skin rashes, and joint pain.

Understanding the mechanism of Type III hypersensitivity is crucial for comprehending the pathogenesis of SLE and its multifaceted effects on various organ systems.