SLE can be distinguished from rheumatoid arthritis on the basis of which finding?

• A. Joint pain
• B. Presence of antinuclear antibodies
• C. Immune complex formation with activation of complement
• D. Presence of anti-dsDNA antibodies

Answer: (C)

SLE is driven by circulating immune complexes formed when autoantibodies target nuclear antigens. These immune complexes deposit in tissues and activate the complement system, causing inflammation and organ damage. This immune complex–mediated, complement-activating process (a type III hypersensitivity mechanism) is a defining pattern of SLE and helps distinguish it from rheumatoid arthritis, where joint destruction is driven more by chronic synovial inflammation and autoantibodies like rheumatoid factor or anti-CCP rather than widespread immune complex deposition and complement activation. So, the finding of immune complex formation with complement activation captures the most characteristic immunopathology of SLE.