IgE is primarily involved in which type of immune responses?

• A. Responds to Parasitic and Allergic Reactions
• B. Crosses Placenta
• C. Opsonizes Bacteria
• D. Immune Functions of Muscle Tissues

Answer: (A)

The main concept here is that IgE is the antibody class specialized for defense against parasites and for mediating allergic reactions. IgE binds to high-affinity receptors on mast cells and basophils; when an antigen (parasite or allergen) cross-links these bound IgE molecules, it triggers degranulation and release of histamine, leukotrienes, and other mediators that drive the inflammatory and allergic responses and help expel parasites. This pathway explains why IgE is central to parasitic infections and allergies. It doesn’t cross the placenta—that function is mainly IgG—and it isn’t primarily responsible for opsonizing bacteria—that role is handled by IgG (and complement). It also has no direct role in immune functions of muscle tissues.