IgM in the primary immune response
Which antibody class is produced first in a primary immune response and, as a pentamer, is especially effective at activating complement?
Answer D: explanation for every choice
A
IgG dominates later, after class switching, and in secondary responses.
B
IgA protects mucosal surfaces and is found in secretions.
C
IgE binds mast cells and mediates allergic responses.
D
Correct. IgM appears first, and its pentameric form binds antigens with high avidity and activates complement strongly.
TakeawayIgM first; IgG later. IgA in secretions. IgE in allergy.
Next question →
Reviewed 2026-11-05 by a medical student. Spot an error? Report it with question ID bb149.