ATI TEAS (Test of Essential Academic Skills) Version 7ScienceHard
A patient experiences a severe allergic reaction, including widespread vasodilation, bronchoconstriction, and increased capillary permeability, leading to a dramatic drop in blood pressure. Which type of hypersensitivity reaction is this most consistent with?
- AType I (Immediate) Hypersensitivity
- BType II (Cytotoxic) Hypersensitivity
- CType IV (Delayed) Hypersensitivity
- DType III (Immune Complex) Hypersensitivity
Show answer & explanationAnswer & explanation
Correct answer: A. Type I (Immediate) Hypersensitivity
The described symptoms (widespread vasodilation, bronchoconstriction, increased capillary permeability, and rapid drop in blood pressure) are characteristic of anaphylaxis, which is the most severe form of Type I (Immediate) Hypersensitivity. This reaction is mediated by IgE antibodies and histamine release from mast cells.
Why the other options are wrong
- B. Type II hypersensitivity involves antibody-mediated cell destruction (e.g., transfusion reactions), not widespread vasodilation and bronchoconstriction.
- C. Type IV hypersensitivity is cell-mediated and delayed (e.g., contact dermatitis, TB test), occurring hours to days later.
- D. Type III hypersensitivity involves immune complex deposition, leading to inflammation (e.g., lupus nephritis), not acute systemic symptoms.
Type I Hypersensitivity
An immediate allergic reaction mediated by IgE antibodies, leading to the release of histamine and other mediators from mast cells and basophils.
- Also known as immediate or anaphylactic hypersensitivity.
- Triggered by allergens like pollen, food, insect venom.
- Symptoms range from mild (hives) to severe (anaphylaxis).
Memory trick: ACID: Anaphylactic, Cytotoxic, Immune-complex, Delayed.