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