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:

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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