Figure 1: Components of type 2 immune response effective against gastrointestinal (GI) helminth parasites. In the primary response, APCs process and present antigens via MHC-class-II, upregulate costimulatory molecules, and, in an IL- 4 milieu, prime naïve T cells to become Th2-cells. Th2-cells and other reactive cells secrete IL-4 and IL-13, promoting B class switching to IgE and IgG1. IgE immune complexes activate basophils and mast cells by crosslinking of FcR. Activated mast cells and basophils secrete soluble mediators inducing changes in smooth muscle contractility, peristalsis, and intestinal permeability increase. IL-4 also induces goblet cell proliferation and mucus production. All of these elements induce a hostile environment for the parasite, provoking their expulsion or their reduction in size and fecundity.