Hypersensitivities are classified by immune mechanism
Type I is mediated by IgE
IgE responses kill helminth (worm) parasites
Hygiene hypothesis
Allergens have certain properties in common
Some allergens are enzymes
Mast cells produce IL-4 to increase IgE production
The location of the stimulus determines the symptoms
Mast cells release many mediator of inflammation
Eosinophils release toxic products plus inflammatory mediators
Allergic reactions have an early and late phase component
In asthma, Th2 cells cause chronic inflammation of the airways
Allergy treatments target many different steps in allergic reactions
