Allergies are familiar to most simply as nuisance responses to innocuous materials such as pollen, yet, at the extreme, allergic reactions to foreign protein can lead to anaphylactic shock and death. In contrast, autoimmune diseases, such as multiple sclerosis, result from the lingering attention of the immune system toward self proteins.
Using a mouse model for multiple sclerosis, termed experimental autoimmune encephalomyelitis (EAE), Pedotti et al. blur the distinctions currently drawn between allergy and autoimmunity by showing that allergic reactions can develop toward self, as well as foreign, proteins. Previous studies have shown that although EAE is driven by a chronic T helper 1 (TH1) class of inflammation, allergic-type TH2 cells also might contribute toward disease pathology. By extending the regime of immunizations that induce EAE to include the recovery phase of the disease, when large numbers of allergic TH2 cells are present, anaphylactic shock and, in some cases, death could be induced. Further examination of the immunizing proteins indicated that the allergic response may have resulted from the persistence of T cells that had not been deleted by the autoantigen within the thymus. — SJS
Nature Immunol.2, 216 (2001).