Hypersensitivity, asthma and research design

Correct answer: C. Type I

• A. Type IV is delayed and cell-mediated, taking 48 to 72 hours. Contact dermatitis to nickel or latex and the tuberculin skin test are the examples.
• B. Type II is antibody-mediated cytotoxicity — IgG or IgM directed at cell-surface antigens, as in transfusion reactions and pemphigus vulgaris.
• C. Correct. Type I is the immediate, IgE-mediated reaction. Antigen cross-links IgE on mast cells and basophils, which degranulate and release histamine within minutes.
• D. Type III is immune complex deposition, seen in serum sickness and lupus.

Note: Latex allergy is worth separating carefully: the dangerous immediate reaction is Type I, while contact dermatitis to glove chemicals is Type IV.

Correct answer: D. IgE

• A. IgG is the most abundant serum immunoglobulin and the only one that crosses the placenta.
• B. IgM is the first antibody produced in a primary response and is the most efficient complement activator.
• C. IgA is the secretory antibody of mucosal surfaces and the dominant immunoglobulin in saliva, where it limits bacterial adherence.
• D. Correct. IgE binds mast cells and basophils; on re-exposure to allergen it triggers degranulation, bronchoconstriction and mucus secretion.

Correct answer: D. The laser treatment

• A. Healing is the 'O', the outcome measured.
• B. The scalpel is the comparison, the 'C', representing standard care.
• C. The patients form the 'P', the population or problem being studied.
• D. Correct. 'I' is the intervention — the new or tested treatment under investigation, here the laser.

Note: A well-built PICO question makes the search strategy almost write itself — each element becomes a search term.