Study Guide - Hypersensitivity.pdf

Study Guide Hypersensitivity A. Define hypersensitivity 1. Increased immune response to the presence of an antigen which produces undesirable clinical effects 2. Note that the four types of hypersens...

Study Guide Hypersensitivity A. Define hypersensitivity 1. Increased immune response to the presence of an antigen which produces undesirable clinical effects 2. Note that the four types of hypersensitivity reactions do not necessarily occur in isolation B. Describe the four types of hypersensitivity, including the time course of each 1. Type I – Immediate Hypersensitivity, Atopy i. IgE is produced instead of IgG (a) Mast cell degranulation (b) Histamine released ii. Response to allergens (a) Normally harmless substances which cause an allergic response (a) Examples include: (i) Shellfish (ii) Pet dander (iii) Dust mites (iv) Peanuts (v) Latex (vi) Insect venom iii. Anaphylaxis = systemic Type I response 2. Type II – Cytotoxic reactions to self-antigens i. Immune response to one’s own tissues (a) Complement activation, agglutination, phagocytosis (a) Examples: (i) Hemolytic diseases of newborn (ii) Myasthenia gravis ii. Cross-reaction between exogenous and endogenous body tissues (a) Examples: (a) Hemolytic streptococci / mitral valve disease (b) Guillian-Barre syndrome 3. Type III – Immune Complex Diseases i. Antigen-antibody complexes depositing around small blood vessels (a) Complement cascade, acute inflammation, tissue injury ii. Examples: (a) Rheumatoid arthritis (b) Nephritis (c) Pericarditis (d) Vasculitis (a) Systemic lupus erythematosus (cell nucleus is antigen) 4. Type IV – Cell-mediated immunity i. Delayed reaction to allergen, usually 48-72 hours (a) Based on macrophage to T-cell interactions which take time to occur ii. Examples: (a) Transplant rejections (b) Delayed contact dermatitis (e.g., poison ivy)