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Hypersensitivity Reaction

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Hypersensitivity Reaction, Gell and Coombs Classification, Coombs and Gell Classification, Type 1 Hypersensitivity, Immediate Hypersensitivity Reaction, Type 2 Hypersensitivity, Cytotoxic Antibody Reaction, Type 3 Hypersensitivity, Immune Complex Reaction, Type 4 Hypersensitivity, Delayed-Type Hypersensitivity, Type 5 Hypersensitivity, Stimulatory Hypersensitivity

  • Definitions
  1. Gell and Coombs Classification of Hypersensitivity Reaction
    1. Categories of Hypersensitivity Response
  • Types
  • 1 - Immediate Hypersensitivity Reaction
  1. Mediated by IgE Antibody to specific antigens
    1. Mast cells stimulated and release histamine
  2. Reaction within one hour of exposure
  3. Examples
    1. Anaphylaxis (e.g. Penicillin)
    2. Urticaria
    3. Angioedema
    4. Anaphylactoid Reaction (e.g. Anaphylactoid Reaction to Radiocontrast)
    5. Atopic Allergy
  • Types
  • 2 - Cytotoxic Antibody Reaction
  1. Mediated by IgG and IgM to specific antigens
  2. Examples
    1. Transfusion Reaction
    2. Rhesus Incompatibility (Rh Incompatibility)
    3. Mycoplasma pneumoniae related cold agglutinins
    4. Hashimoto's Thyroiditis
    5. Goodpasture's Syndrome
    6. Delayed transplant graft rejection
  • Types
  • 3 - Immune Complex Reaction
  1. Antigen-Antibody complexes deposit in tissue
  2. Reaction within 1-3 weeks after exposure
  3. Examples
    1. Systemic Lupus Erythematosus
    2. Erythema Nodosum
    3. Polyarteritis Nodosa
    4. Arthus Reaction (e.g. Farmer's Lung)
    5. Rheumatoid Arthritis
    6. Elephantiasis (Wuchereria bancrofti reaction)
    7. Jarisch-Herxheimer Reaction
    8. Serum Sickness
  • Types
  • 4 - Delayed-Type Hypersensitivity
  1. Mediated by T-Lymphocytes to specific antigens
    1. Involves major histocompatibility complex (MHC)
    2. Reaction within 2-7 days after exposure
  2. Examples
    1. Mantoux Test (PPD)
    2. Allergic Contact Dermatitis (e.g. Nickel allergy)
  • Types
  • Other allergy mediated reactions
  1. Stimulatory Hypersensitivity
    1. Humoral Antibody activates receptor sites
    2. Example: Thyrotoxicosis (TSH autoantibodies)
  2. Fas/Fas Ligand-induced apoptosis
    1. Example: Stevens Johnson Syndrome
  3. T-Cell activation
    1. Example: Sulfonamide induced Morbilliform rash
  • References
  1. Roitt (1988) Essential Immunology, Blackwell,p. 193-214
  2. Riedl (2003) Am Fam Physician 68:1781-90 [PubMed]