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Pathology · single question

Lichen planus is best classified as which type of immune reaction?

  1. T-cell mediated autoimmune reaction against basal epithelial keratinocytes
  2. Immune complex-mediated (Type III) hypersensitivity
  3. IgE-mediated (Type I) hypersensitivity
  4. B-cell mediated autoimmune disorder
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Correct answer: A. T-cell mediated autoimmune reaction against basal epithelial keratinocytes

  • A. Correct. Lichen planus is a T-lymphocyte mediated (Type IV cell-mediated) autoimmune reaction. CD8+ cytotoxic T cells attack basal epithelial keratinocytes, causing basal cell liquefaction degeneration and formation of Civatte bodies (apoptotic keratinocytes). This leads to the characteristic histopathological features.
  • B. Type III (immune complex) hypersensitivity includes SLE and serum sickness — not lichen planus.
  • C. IgE-mediated (Type I) hypersensitivity causes anaphylaxis and allergic reactions — not lichen planus.
  • D. While antibodies may be found in lichen planus, the driving mechanism is T-cell cytotoxicity against basal keratinocytes.

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