Micro & Immunology · single question
3 days after a latex rubber dam appointment, the same child presents with new burning lesions around the mouth. What type of hypersensitivity reaction has occurred?
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Correct answer: A. Type IV hypersensitivity reaction
The DELAYED reaction occurring 48-72 hours later (3 days) with burning lesions around the mouth is characteristic of a TYPE IV (cell-mediated / delayed-type) hypersensitivity reaction. Type IV is T-cell mediated (not antibody-mediated) and produces contact dermatitis-like reactions. It takes 48-72 hours because T-cell sensitization and cytokine release are slower than immediate IgE responses. Contact dermatitis from latex = classic Type IV.
- A. CORRECT. TYPE IV (delayed/cell-mediated) hypersensitivity occurs 48-72 hours after exposure. It is mediated by sensitized T lymphocytes (not antibodies) releasing cytokines. The burning skin lesions 3 days after latex contact = classic Type IV contact hypersensitivity (contact dermatitis).
- B. INCORRECT. Type III (immune complex) involves antigen-antibody complexes depositing in tissues — examples: lupus, serum sickness. Delayed contact reactions are Type IV.
- C. INCORRECT. Type I (IgE-mediated) is IMMEDIATE (within minutes) — urticaria, rhinitis, anaphylaxis. The initial acute reaction was Type I.
- D. INCORRECT. Type II (cytotoxic) involves antibodies targeting cell surfaces — examples: hemolytic anemia, Goodpasture syndrome. Not relevant here.
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