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