Fig. 9: Opsonization of a Helminth by IgE and Eosinophils
A major function
of the cytokines produced
by Th2 cells is to enable B-lymphocytes to activate eosinophils
and produce increased amounts of a class of antibodies called IgE against
helminths (parasitic worms) and arthropods. IgE act as an opsonizing antibody
to stick phagocytic eosinophils to helminths for extracellular killing of
the helminths. The Fab portion of IgE reacts with epitopes on the helminth
while the Fc portion binds to Fc receptors of activated eosinophils. The lysosomal
proteases of eosinophils are able to destroy the tough integument of helminths.
IgE also promotes inflammation to recruit phagocytes.