1 / 18

Hypersensitivity Reactions:

Hypersensitivity Reactions:. Definitions: Hypersensitivity reactions : inflammatory immune responses induced by repeated antigen exposure resulting in host tissue damage. Allergen : is a nonparasitic antigen capable of stimulating hypersensitivity reactions. Types of Hypersensitivity:.

drew-hoover
Download Presentation

Hypersensitivity Reactions:

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Hypersensitivity Reactions: Definitions: Hypersensitivity reactions: inflammatory immune responses induced by repeated antigen exposure resulting in host tissue damage. Allergen: is a nonparasitic antigen capable of stimulating hypersensitivity reactions.

  2. Types of Hypersensitivity: Hypersensitivity reactions are divided according to mechanism of action into four groups: 1-Type I (Immediate hypersensitivity). 2-Type II (Cytotoxic hypersensitivity). 3-Type III (Immune complex hypersensitivity). 4-Type IV (Cell-mediated hypersensitivity).

  3. Types of Allergen: Exogenous: 1- Animal products. 2- Drugs ( penicillin) 3- Food : Egg albumen, Corn, legumes (peanuts, soybeans), milk, and seafood. 4- Insect venom. 5- Mold spores. 6- Plant pollens. Endogenous: -Self antigen.

  4. Type I Hypersensitivity: -Commonly known as allergic or immediate hypersensitivity. -Two types according to affected body sites: 1-Localized reaction: Skin, eye, Nasopharynx, Bronchopulmonary, and GIT. 2-Systemic reaction: In Bloodstream. -The reaction takes 15-30 minutes to appear as inflammatory response. -It could appear as a delayed response (10-12 hours later). -Examples: Eczema, Urticaria, Hay fever, Asthma.

  5. Mechanism of inflammation in Hypersensitivity Type I: Sensitization phase: 1-Exposure to allergen. 2-Isotype switching (IL-4, IL-13 activity). 3-Sensitization of Mast cell by IgE (FcεRI). Effector phase: 1-IgE Cross-linking. 2-Mast cell degranulation. 3-Release of vasoactive amines, Lipids, and cytokines.

  6. Type I Hypersensitivity (sensitization phase): N

  7. Type I Hypersensitivity (Effector phase): N

  8. Mast cell inflammatory mediators and their action: 1- Biogenic amines ( histamines): A-Bronchiole constriction, and mucus secretion from Goblet cell. B- Endothelial vasodilation ; increased vascular permeability, and vasoconstriction. 2- Lipid mediators: A-Leukotriene C4,and D4 ; similar to histamine effect. B-PAF (platelet aggregation: microthrombosis) C-Prostaglandins D2 :edema and pain. 3-Cytokines:TNF.

  9. Clinical examples on Type I Hypersensitivity: 1-Localized reaction in Skin: UrticariaEczema 2-Systemic Anaphylaxis: In bloodstream. Lethal effect.

  10. Type II Hypersensitivity: -Known as Cytotoxic Hypersensitivity. -Allergen could be: 1-Endogenous: Cell surface protein. 2-Exogenous: Drug metabolite adsorbed onto cell membrane. -Sites of occurrence of Type II reactions: 1-On cell surface (Example: RBCs). 2-Within extracellular matrix (Example:Basement memb).

  11. Mechanism of inflammation in Hypersensitivity Type II: -IgG ,IgM , Complement, and Cytotoxic cells are involved in this type of inflammation.

  12. Clinical Examples on Type II Hypersensitivity: 1-Immune Hemolytic Anemia: A-Alloimmunehemolyticanemia. :Erythroblastosisfetalis B-Autoimmunehemolyticanemia. : Blood transfusion anemia. 2-Goodpasture’s syndrome (nephritis). 3-Graves Disease.

  13. Type III Hypersensitivity: -Immune Complex hypersensitivity. -Soluble Immune complexes: (IgG- short peptide-IgG) or (IgG-Animal sera-IgG). -Two types: 1-Localized in skin: Example: Arthus reaction. Intradermal injection of antigen in skin; necrotizing vasculitis . 2-Systemic: Example: Serum sickness disease. -Types of Allergen: 1-Exogenous. 2-Endogenous: self antigen.

  14. Mechanism of Inflammation in Type III Hypersensitivity: -Immune complex (IgG), complement, and Neutrophils are involved.

  15. Clinical Examples on Type III Hypersensitivity: 1-Serum sickness disease that associated with: -Some types of Food allergy. -The prophylactic Vaccine. 2-Systemic lupus erythematosis. 3-Rheumatoid arthritis.

  16. Type IV Hypersensitivity: - known as cell mediated or delayed type hypersensitivity. - The classical example of this hypersensitivity is tuberculin (Montoux) reaction which peaks 48 hours afterthe injection of antigen (tuberculin). -Three types: 1-Contact dermatitis: toxic sensitizer or neoantigen. 2-Delayed type hypersensitivity(DTH): Granulomatous inf. 3-T cell mediated cytotoxicity.

  17. Mechanism of inflammation in type IV: -DTH cell,and toxin or neoantigen are involved.

  18. Clinical example: Tuberculin test:

More Related