Wegener's granulomatosis is a ________ mediated hypersensitivity with _________ in 95% of cases.

• A. B cell mediated; MPO-ANCA
• B. T cell mediated; PR3-ANCA
• C. Immune complex mediated; ANCA
• D. Autoantibody independent; ESR

Answer: (B)

Wegener's granulomatosis is driven by autoimmunity where autoantibodies against neutrophil cytoplasmic antigens play a central role, and the granulomatous tissue damage is shaped by T cell–mediated responses. In about 95% of cases, antibodies against proteinase 3 (PR3-ANCA, formerly c-ANCA) are present. These PR3-ANCA antibodies bind neutrophils and trigger activation and degranulation, leading to endothelial injury and necrotizing vasculitis, while the granulomatous inflammation is largely produced by T cells (a Th1-type response) in affected tissues. Thus, the best description is a T cell–driven immune process with PR3-ANCA positivity in the vast majority of cases.