Which category of hypersensitivity (Types 1-4) are immediate hypersensitivities, occurring rapidly and eliciting especially severe responses to an antigen?

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Multiple Choice

Which category of hypersensitivity (Types 1-4) are immediate hypersensitivities, occurring rapidly and eliciting especially severe responses to an antigen?

Immediate hypersensitivity is Type I. It is driven by IgE antibodies bound to mast cells and basophils; when the antigen appears, it cross-links those surface IgE molecules and triggers rapid degranulation, releasing histamine and other mediators. This causes quick symptoms such as swelling, redness, bronchoconstriction, and mucus production, and in severe cases can lead to systemic anaphylaxis within minutes. This rapid, IgE-driven response distinguishes it from the other hypersensitivity types: cytotoxic Type II and immune complex–mediated Type III involve different antibodies and timing, while delayed-type Type IV is T-cell–mediated and develops over 24–72 hours.

Immediate hypersensitivity is Type I. It is driven by IgE antibodies bound to mast cells and basophils; when the antigen appears, it cross-links those surface IgE molecules and triggers rapid degranulation, releasing histamine and other mediators. This causes quick symptoms such as swelling, redness, bronchoconstriction, and mucus production, and in severe cases can lead to systemic anaphylaxis within minutes. This rapid, IgE-driven response distinguishes it from the other hypersensitivity types: cytotoxic Type II and immune complex–mediated Type III involve different antibodies and timing, while delayed-type Type IV is T-cell–mediated and develops over 24–72 hours.

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