The document discusses the different types of hypersensitivity reactions and factors that influence allergies. Type I is allergy and anaphylaxis mediated by IgE antibodies. Genetic and environmental factors like exposure to pathogens, pollution, and diet changes impact allergy risk. Type II involves cytotoxic antibodies destroying cells, Type III involves immune complex deposition, and Type IV is delayed cell-mediated hypersensitivity. Mast cells, eosinophils, and house dust mites are also mentioned as playing roles in hypersensitivity reactions.

1. Allergy and Hypersensitivity

4. 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

9. Genetics factors and Allergies Cytokines and their receptors MHC II genes Other polymorphisms

11. 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

13. Mast Cell mediators

14. Eosinophil mediators

15. House Dust Mite Ag

20. 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

21. Type III hypersensitivity: immune complex

23. Type IV hypersensitivity: delayed or cell-mediated