Wednesday, July 12, 2017

Hypersensitivity - Different Types

Type I Anaphylactic

  • antigen reacts with IgE bound to mast cells
  • anaphylaxis, atopy (e.g. asthma, eczema and hayfever)

Type II Cell bound

  • IgG or IgM binds to antigen on cell surface
  • autoimmune haemolytic anaemia, ITP, Goodpasture's, pernicious anemia, acute hemolytic transfusion reactions, rheumatic fever, bullous pemphigoid, pemphigus vulgaris.

Type III Immune complex

  • free antigen and antibody (IgG, IgA) combine
  • serum sickness, systemic lupus erythematosus, poststreptococcal glomerulonephritis, extrinsic allergic alveolitis (especially acute phase)

Type IV Delayed hypersensitivity

  • T cell mediated
  • tuberculosis, tuberculin skin reaction, graft versus host disease, allergic contact dermatitis, scabies, extrinsic allergic alveolitis (especially chronic phase), multiple sclerosis, GuillainBarre syndrome

In recent times a further category has been added:

Type V

  • antibodies that recognize and bind to the cell surface receptors, either stimulating them or blocking ligand binding
  • Graves' disease, myasthenia gravis

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