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Hypersensitivity - Comprehensive Review Type | Hypersensitivity - “Anaphylactic Hypersensitivity” - Associated with common “allergies” - Mast Cells. Basophils. and Eosinophils involved - Involves Antibodies: IgE - Complement is not involved Mast Cell Basophil Eosinophil Two Phases: A: Sensitization - APCs process antigens and present them to Th2 cells, which induce B cells to produce allergen-specific IgE by producing IL-I3 & IL-4. - IgE binds to FceRI receptors on mast cells and basophils. B: Activation - Allergen cross links on two adjacent cell-bound IgE molecules. - Basophil/Mast cell degranulates. Cell mediators bind to target cell and symptoms are produced. SENSITIZATION ACTIVATION allergen? cz an ae ALS “Ys ar 5 eral . ‘ wal Reespter er ° Degranviation Clinical Examples of Hypersensitivity |: + Hay Fever. Hives. Anaphylaxis. Eczema, Food allergies, Allergic Asthma. Treatments: - Avoidance of allergen - Drug therapy (antihistamines. bronchodilators. mast cell stabilizers, corticosteroids, epinephrine. - Monoclonal IgE Antibody - Allergy Immunotherapy (Gradual exposure) Testing: - In Vivo skin test - Allergen-specific IgE testing Type Il Hypersensitivity - "Antibody-Mediated Cytotoxic Hypersensitivity" - IgM or IgG are produced against. antigens found on cell surfaces. resulting in either: - A: Destruction of the target cell. - B: Inhibition of the target cell function. - C: Increased target cell Function. - 3 Ways for Cell Destruction to occur: A: Complement - Activation of the complement pathway resulting in cell lysis by formation of the MAC. B: Opsonization - Coating of the cell surface in antibodies promoting opsonization and phagocytosis. A: 4g Clars Unit -> Formation of the MAC C: Antibody-Dependent Cell-Mediated Cytotoxicity - IgG binds to receptors on target cell, and then also to the Fc receptors of Macrophages or NK cells, resulting in the release of cytotoxic enzymes. B: Phagocytosis C: Release of Cytotoxic enzymes 
