hyper sensitivity and its types unit .pptx

hyper sensitivity and its type

1. HYPERSENSITIVITY ALI ASGHAR LECTURER-NURSING MICROBIOLOGY BECON-SMBBMU-LARKANA 1

2. HYPERSENSITIVITY (Allergy) Refers to undesirable reactions produced by the normal immune system, including allergies and autoimmunity. Allergy is hypersensitive state acquired through exposure of allergen. These are basically IgE mediates Urticaria , bronchospasm, angioedema ,anaphylaxis , and atopy Allergens may be introduced by skin contact, ingestion (food), inhalation (e.g., pollen), or drugs. Common allergic conditions or symptoms include eczema or atopic dermatitis, allergic rhinitis, dermatitis, bronchial asthma,urticaria and food allergy . 2

3. 1. Type-I Anaphylactic hypersensitivity MECHANISMS OF ALLERGY (Anaphylactic hypersensitivity ) Occur in individuals who have inherited very high level of IgE When exposed to allergen , activate Mast cells (mediates inflamatory response)and Basophiles ( deffense from allergens) to release HISTAMINE which constrict air way and vasodilatation. This leads to shock called anaphylactic shock. Onset is sudden. E.g penicillin allergy

4. 2. TYPE-II cytotoxic hypersensitivity Also known as cytotoxic hypersensitivity. „ It is induced by IgG or IgM antibodies „ The antibodies are usually directed against self antigens When antibody reacts with an antigen on cell surface, that cell is marked for the destruction by number of mechanisms, e.g. phagocytosis or by lytic enzymes. The procedure is usually for elimination of virus or bacteria, but antibodies are directed against self-antigen the result is destruction of body’s own tissues (Autoimmune Disease).Onset is immediate/ sudden 4

5. Examples Auto immune hemolytic anemia(RBC destroy ) Pernicious anemia (RBC, vB12) Immune thrombocytopenia(low platelets) Transfusion reactions Hashimoto's thyroiditis Graves' disease (hyperthyroidism) Hemolytic disease of the newborn(sever form of enemia ) (type of blood mother and baby incompatible)

6. TYPE-III Immune-complex-mediated hypersensitivity also known as serum sickness. Occurs at least one week after first exposure. This antigen-antibodies complex (immune complex), usually cleared by phagocytosis. If not cleared immune-complex deposited in tissue i.e kidneys, joint, heart skin,vessels where they cause inflammatory reaction. E.g Glomerulonephritis, R heumatoid arthritis, V asculitis etc Onset is 4-8 hours. 6

7. TYPE-IV Delayed type hypersensitivity Unlike type I, II, III, it does not involve antibodies, but due to overreaction of T-Cells to an antigen. It causes to release Cytotoxic T-Cells to eliminate antigen. When S-T-cells are inappropriate in action, cytotoxic T-Cells damage normal tissues. E.g. T.B, leprosy and graft rejection. Onset is 24-48 hours 7