Question:
The hypersensitivity reaction that typically appears 24 - 48 hours after antigen exposure and is mediated by sensitized T lymphocytes is
The hypersensitivity reaction that typically appears 24 - 48 hours after antigen exposure and is mediated by sensitized T lymphocytes is
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The Gell and Coombs classification divides hypersensitivity reactions into four types. The key difference is the immune mechanism (antibody-mediated versus cell-mediated) and the timing of the reaction.
Updated On: Jun 24, 2026
- Type I hypersensitivity
- Type II hypersensitivity
- Type III hypersensitivity
- Type IV hypersensitivity
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The Correct Option is D
Solution and Explanation
Concept:
The Gell and Coombs classification divides hypersensitivity reactions into four types. The key difference is the immune mechanism (antibody-mediated versus cell-mediated) and the timing of the reaction.
Step 1: A reaction that takes 24–48 hours to develop and is driven by sensitized T lymphocytes (not antibodies) is the classic description of Type IV (delayed-type) hypersensitivity. The contact dermatitis and the tuberculin (Mantoux) skin test are typical examples.
Why the other choices are wrong: Type I is immediate (IgE-mediated, within minutes). Type II is antibody-mediated cytotoxicity. Type III involves immune complexes. None of these are delayed, T-cell-mediated reactions.
Answer: Option (4) — Type IV hypersensitivity is the delayed, T-cell-mediated reaction. (4)
The Gell and Coombs classification divides hypersensitivity reactions into four types. The key difference is the immune mechanism (antibody-mediated versus cell-mediated) and the timing of the reaction.
Step 1: A reaction that takes 24–48 hours to develop and is driven by sensitized T lymphocytes (not antibodies) is the classic description of Type IV (delayed-type) hypersensitivity. The contact dermatitis and the tuberculin (Mantoux) skin test are typical examples.
Why the other choices are wrong: Type I is immediate (IgE-mediated, within minutes). Type II is antibody-mediated cytotoxicity. Type III involves immune complexes. None of these are delayed, T-cell-mediated reactions.
Answer: Option (4) — Type IV hypersensitivity is the delayed, T-cell-mediated reaction. (4)
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