Pathology · single question
Type I hypersensitivity reactions are mediated primarily by which immunoglobulin?
Show answer and explanation
Correct answer: D. IgE
- A. IgG mediates Type II and Type III hypersensitivity reactions and opsonization.
- B. IgA is the primary immunoglobulin in mucosal secretions (saliva, tears, breast milk); it is not the mediator of Type I hypersensitivity.
- C. IgM is the first antibody produced in a primary immune response and activates complement; not the mediator of Type I hypersensitivity.
- D. Correct. Type I (immediate) hypersensitivity is mediated by IgE antibodies bound to mast cells and basophils. Upon re-exposure to allergen, crosslinking of IgE triggers degranulation and release of histamine, prostaglandins, and leukotrienes.