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Pharmacology · single question

Which pairing of hypersensitivity reactions is correct?

  1. Type I = immediate IgE-mediated (anaphylaxis); Type IV = delayed T-cell-mediated (contact allergy)
  2. Type I = delayed; Type IV = immediate
  3. Both Type I and Type IV are antibody-mediated
  4. Type IV is IgE-mediated
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Correct answer: A. Type I = immediate IgE-mediated (anaphylaxis); Type IV = delayed T-cell-mediated (contact allergy)

Type I is immediate and IgE-mediated (anaphylaxis, allergic reactions to latex or penicillin within minutes). Type IV is delayed (24 to 72 hours) and T-cell-mediated (contact dermatitis, e.g., to nickel or latex accelerators, and the tuberculin/PPD reaction).Other options: The reversed and 'both antibody-mediated' options are incorrect; Type IV is cell-mediated, not IgE.Key exam takeaway: Type I = immediate IgE (anaphylaxis); Type IV = delayed T-cell (contact allergy, PPD). Type II = cytotoxic IgG/IgM; Type III = immune complex.

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