IgE is medically impoant for two reasons: It mediates immediate (anaphylactic) hypersensitivity, and It paicipates in host defenses against ceain parasites (e.g., helminths ). The Fc region of IgE binds to the surface of mast cells and basophils. IgE does not fix complement and does not cross the placenta. In contrast to other immunoglobulins, IgE is heat labile and gets inactivated by heating at 56degC Ref: Levinson W. (2012). Chapter 59. Antibodies. In W. Levinson (Ed), Review of Medical Microbiology & Immunology, 12e.