A 6-year-old child develops generalized urticaria, bronchospasm, and hypotension within minutes of a penicillin injection. Which immunoglobulin class is primarily responsible for this reaction?
- A IgG
- B IgE ✓
- C IgM
- D IgA
Correct answer: B. IgE
Explanation
This is a classic Type I (immediate) hypersensitivity reaction mediated by IgE antibodies bound to high-affinity FcεRI receptors on mast cells and basophils. On re-exposure to the antigen, cross-linking of adjacent IgE molecules triggers degranulation, releasing histamine, leukotrienes, and prostaglandins. The reaction characteristically occurs within seconds to minutes and can progress to anaphylaxis with cardiovascular collapse.
Reference: Ananthanarayan & Paniker's Textbook of Microbiology, 11th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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