Allergy and Hypersensitivity

Type I hypersensitivity: anaphylactic and atopic

(Allergy)

•Allergens are small Ags, usually inocuous

•TH2 response intitiated

•B cells produced IgE

•IgE binds mast cells, basophils, eosinophils

• Genetics factors and Allergies– Cytokines and their receptors– MHC II genes– Other polymorphisms

Increase in Atopic Allergy

• Environmental factors– Exposure to pathogens in childhood

• Measles, HepA, tuberculosis exposure beneficial?

– Environmental pollution• Eg. Children in Hale, East Germany

– Allergen levels• No evidence of rise

– Dietary changes• No evidence of effect

Mast Cell mediators

Eosinophil mediators

House Dust Mite Ag

Type II hypersensitivity:cytotoxic

• Cell-reactive antibodies

• Cross-reactivity

• Cell surface adhesion of foreign antigen…cell destruction

• Complement and phagocytosis activated

• Red blood cells and platelets most common target

Type III hypersensitivity:immune complex

Type IV hypersensitivity:delayed or cell-mediated