IgE
It occurs as a monomer and has an extra domain in the constant region.

Properties
1. It is the least common serum Ig, but it binds very tightly to Fc receptors on basophils and mast
cells even before interacting with Ags.
2. It is involved in allergic reactions because it binds to basophils and mast cells.
3. It plays a role in parasitic helminthic diseases. Serum levels rise in these diseases. Eosinophils
have Fc receptors for IgEs and when eosinophoils bind to IgEs coated helminthes death of the
parasite results.