Background: Although anaphylaxis is classically mediated by IgE, FcϵRI, mast cells, and
histamine, several rodent studies suggest that an alternative pathway involving IgG, FcγRIII,
macrophages and platelets, and platelet-activating factor (PAF) may be more important in
the anaphylactic response to antigen challenge. Objectives: We sought to determine the
relative roles of the classical and alternative pathways of anaphylaxis in a mouse model
characterized by mastocytosis and a high level of antigen-specific IgE antibody. Methods …