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