**Question:** All are TRUE about Antineutrophil Cytoplasmic Antibodies, EXCEPT:

A. Antineutrophil cytoplasmic antibodies (ANCAs) are directed against neutrophil enzymes.
B. ANCAs are commonly found in healthy individuals.
C. ANCAs are associated with systemic lupus erythematosus (SLE).
D. ANCAs do not play a role in vasculitis.

**Correct Answer: B.**

**Core Concept:** Antineutrophil cytoplasmic antibodies (ANCAs) are autoantibodies that bind to neutrophil proteins, particularly the cytoplasmic enzymes, such as myeloperoxidase (MPO) and proteinase 3 (PR3). These antibodies are often associated with vasculitis, a group of conditions characterized by inflammation of blood vessels.

**Why the Correct Answer is Right:** ANCAs are not commonly found in healthy individuals. In fact, they are typically elevated in patients with systemic vasculitis, such as granulomatosis with polyangiitis (Wegener's granulomatosis), microscopic polyangiitis, and eosinophilic granulomatosis with polyangiitis. ANCAs are not typically detected in healthy individuals, making option B incorrect.

**Why Each Wrong Option is Incorrect:**

**A.** Antineutrophil cytoplasmic antibodies are indeed directed against neutrophil enzymes, specifically MPO and PR3. This option is correct.

**C.** ANCAs are associated with several types of vasculitis, including Wegener's granulomatosis, microscopic polyangiitis, and eosinophilic granulomatosis with polyangiitis. However, ANCAs are not solely restricted to these conditions. They can also be found in other autoimmune diseases and infections, which makes this option incorrect.

**D.** ANCAs do play a role in vasculitis pathogenesis. ANCAs can cause endothelial cell damage and contribute to the immune response against neutrophils, leading to vasculitis. This option is correct.

**Clinical Pearl:** ANCAs are important biomarkers in the diagnosis and monitoring of certain vasculitis conditions. Their detection can guide treatment decisions and assess disease activity. However, ANCAs should not be the sole diagnostic criterion as they can be found in other diseases and infections.