Thursday, October 16, 2014

Types of Hypersensitivity with Examples

Hypersensitivity refers to an undesirable reaction of  the body's immune system. This reaction may be a kind of allergy or may be the manifestation of an autoimmune condition. Medically, hypersensitivity has been divided into four types:

  • Type I hypersensitivity- anaphylactic and atopic
  • Type II hypersensitivity- antibody mediated
  • Type III hypersensitivity- Immune complex medicated
  • Type IV hypersensitivity- delayed or T-cell mediated
Type of hypersensitivity
Examples
Type I hypersensitivity- anaphylactic and atopic

Antigen provokes presensitized mast cells and basophils through IgE, causing the release vasoactive amines like histamine. Histamine acts on postcapillary venules.
Anaphylaxis


  • Bee stings
  • Food allergy
  • Asthma
  • Rhinitis
  • Hay fever
  • Eczema
  • Hives


Drug allergy

Allergic or atopic conditions like:

Type II hypersensitivity- antibody mediated

Antibodies IgM or IgG bind to the antigen present on the enemy’s cell and trigger lysis or phagocytosis. Three mechanisms can be explained: opsonizing the cells or activating the complement system, recruiting neutrophils and macrophages for tissue damage, and binding to the normal cellular receptors to cause dysfunction.

  • Hemolytic anemia
  •  Pernicious anemia 
  • Erythroblastosis fetalis 
  • ITP (Idiopathic thrombocytopenic purpura)
  •  Acute hemolytic transfusion reaction
  • Rheumatic fever
  •  Goodpasture’s syndrome
  • Bullous pemphigoid
  •  Pemphigus vulgaris 
  • Myasthenia gravis
  •  Grave’s disease
  •  SLE (only blood manifestations)

Type III hypersensitivity- Immune complex medicated

Immune complexes provoke complement system which in turn attacks neutrophils. Neutrophils release lysosomal enzymes, causing tissue damage.

  • SLE (Systemic lupus erythematosus) 
  • Rheumatoid arthritis 
  • Polyarteritis nodosum 
  • Serum sickness 
  • Arthus reaction (swelling and inflammation after certain vaccine administration) 
  • Farmer’s lung (Hypersensitivity pneumonitis) 
  • Post streptococcal glomerulonephritis
Type IV hypersensitivity- delayed or T-cell mediated


Sensitized lymphocytes encounter/confront antigens by releasing lymphokines which in turn activate macrophages.

  • Type I diabetes mellitus 
  • Multiple sclerosis 
  • GBS (Guillain-Barre syndrome) 
  • PPD test for tuberculosis 
  • Contact dermatitis (e.g. poison ivy, nickel allergy, skin tattooing) 
  • Graft-versus-host (GVH) disease 
  • Hashimoto’s thyroiditis


The table given below describes each type of hypersensitivity with examples:


Keywords: Type I hypersensitivity, Anaphylaxis, Atopic conditions, Type II hypersensitivity, Antibody mediated reaction, Type III hypersensitivity, Immune complex medicated reaction, Type IV hypersensitivity- delayed or T-cell mediated

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