Prosthodontics & Occlusion · single question
Same patient with metal RPD contact dermatitis — what is the Type IV mechanism?
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Correct answer: D. Delayed and cell-mediated
- A. Antibody + complement mediated = Type II (cytotoxic) — not the RPD contact dermatitis mechanism.
- B. Immediate + IgE-mediated = Type I (anaphylaxis/atopy) — NOT the mechanism of contact dermatitis from metal.
- C. Immune complex mediated = Type III (serum sickness/Arthus reaction) — not the mechanism of contact dermatitis.
- D. Type IV hypersensitivity is DELAYED (takes 24-72 hours) and CELL-MEDIATED (T-lymphocytes, not antibodies). Sensitized CD4+ T-helper cells recognize the metal hapten-protein complex and release cytokines that activate macrophages, causing the inflammatory reaction. This is the mechanism of contact dermatitis from nickel in the RPD framework.
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