Hypersensitivity

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Hypersensitivity

Hypersensitivity (also called hypersensitivity reaction) refers to undesirable (damaging, discomfort-producing and sometimes fatal) reactions produced by the normal immune system. Hypersensitivity reactions require a pre-sensitized (immune) state of the host. The four-group classification was expounded by P. H. G. Gell

Philip George Houthem Gell

Philip George Houthem Gell was an immunologist working in postwar Britain.Together with Robin Coombs, he developed the Gell-Coombs classification. He was elected as Fellow of the Royal Society in 1969....
and Robin Coombs

Robin Coombs

Robert Royston Amos Coombs, , was a British immunology, co-discoverer of the Coombs test used for detecting antibody in various clinical scenarios, such as Rh disease and blood transfusion....
in 1963.

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Comparison of hypersensitivity types|-

Type

Alternative names

Often mentioned disorders

Mediators

Type I hypersensitivity

Type I hypersensitivity is an allergic reaction provoked by reexposure to a specific type of antigen referred to as an allergen.Exposure may be by ingestion, inhalation, injection , or direct contact....

Allergy

Allergy is a Disorder of the immune system often also referred to as atopy. Allergic reactions occur to Natural environmental substances known as allergens; these reactions are Acquired disorder, predictable and rapid....
(immediate)

Delayed-type hypersensitivity (DTH), cell-mediated immune memory response

Cell-mediated immunity

Cell-mediated immunity is an immune response that does not involve antibodies or complement system but rather involves the activation of macrophages, natural killer cells , antigen-specific cytotoxic T-lymphocytes, and the release of various cytokines in response to an antigen....
, antibody-independent

The use of Type 5 is rare.

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Philip George Houthem Gell

Robin Coombs

Coombs and Gell classification

**Comparison of hypersensitivity types**|-
Type	Alternative names	Often mentioned disorders	Mediators
1 Type I hypersensitivity Type I hypersensitivity is an allergic reaction provoked by reexposure to a specific type of antigen referred to as an allergen.Exposure may be by ingestion, inhalation, injection , or direct contact....	Allergy Allergy Allergy is a Disorder of the immune system often also referred to as atopy. Allergic reactions occur to Natural environmental substances known as allergens; these reactions are Acquired disorder, predictable and rapid.... (immediate)	Atopy Atopy Atopy or atopic syndrome is an allergic hypersensitivity affecting parts of the body not in direct contact with the allergen.... Anaphylaxis Anaphylaxis Anaphylaxis is an acute Circulatory system and very severe Type I hypersensitivity allergy reaction in humans and other mammals. The term comes from the Greek words a?a ana and f??a??? phylaxis .... Asthma Asthma Asthma is a common chronic obstructive pulmonary disease, in which the Lung constrict, become inflammation, and are lined with excessive amounts of thickened mucus, often in response to one or more triggers....	IgE Immunoglobulin E In biology, Immunoglobulin E is a class of antibody that has only been found in mammals. It plays an important role in allergy, and is especially associated with type 1 hypersensitivity....
2 Type II hypersensitivity In type II hypersensitivity the antibodies produced by the immune response bind to antigens on the patient's own cell surfaces. The antigens recognized in this way may either be intrinsic or extrinsic ....	Cytotoxic, antibody-dependent	Autoimmune hemolytic anemia Autoimmune hemolytic anemia Autoimmune hemolytic anemia is a type of hemolytic anemia where the body's immune system attacks its own red blood cells , leading to their destruction .... Thrombocytopenia Thrombocytopenia Thrombocytopenia is the presence of relatively few platelets in blood.Generally speaking, in humans, a normal platelet count ranges from 150,000 and 450,000 per mm3.... Erythroblastosis fetalis Goodpasture's syndrome Goodpasture's syndrome Goodpasture?s syndrome is a rare condition characterised by rapid destruction of the kidneys and haemorrhaging of the lungs. Although many diseases can present with these symptoms, the name Goodpasture?s syndrome is usually reserved for the autoimmune disease produced when the patient?s immune system attacks cells presenting the Goodpasture...	IgM Immunoglobulin M Immunoglobulin M, or IgM for short, is a basic antibody that is present on B cells. It is the primary antibody against ABO blood group system and ABO blood group system antigens on red blood cells.... or IgG Immunoglobulin G Immunoglobulin G is a monomeric immunoglobulin, built of two Antibody#Heavy chain ? and two Antibody#Light chain. Each IgG has two antigen binding sites.... (Complement Complement system The complement system is a biochemical cascade that helps clear pathogens from an organism. It is part of the larger immune system that is not adaptable and does not change over the course of an individual's lifetime; as such it belongs to the innate immunity.... )
3 Type III hypersensitivity Type III hypersensitivity occurs when antigens and antibodies are present in roughly equal amounts, causing extensive cross-linking....	Immune complex Immune complex An immune complex is the combination of an epitope with an antibody directed against that epitope. The bound antigen and the binding antibody are referred to as a single entity in this state.... disease	Serum sickness Serum sickness Serum sickness is a reaction to proteins in antiserum derived from an animal source. It is a type of hypersensitivity, specifically immune complex hypersensitivity .... Arthus reaction Arthus reaction In immunology, the Arthus reaction is a type of local type III hypersensitivity reaction. Type III hypersensitivity reactions are immune complex-mediated, and involve the deposition of antigen/antibody complexes mainly in the blood vessel walls, serosa , and glomeruli.... SLE Systemic lupus erythematosus Systemic lupus erythematosus is a chronic Autoimmunity connective tissue disease that can affect any part of the body. As occurs in other autoimmune diseases, the immune system attacks the body?s cells and tissue, resulting in inflammation and tissue damage....	IgG Immunoglobulin G Immunoglobulin G is a monomeric immunoglobulin, built of two Antibody#Heavy chain ? and two Antibody#Light chain. Each IgG has two antigen binding sites.... (Complement Complement system The complement system is a biochemical cascade that helps clear pathogens from an organism. It is part of the larger immune system that is not adaptable and does not change over the course of an individual's lifetime; as such it belongs to the innate immunity.... )
4 Type IV hypersensitivity Type IV hypersensitivity is often called delayed type hypersensitivity as the reaction takes two to three days to develop. Unlike the other types, it is not antibody mediated but rather is a type of cell-mediated response....	Delayed-type hypersensitivity (DTH), cell-mediated immune memory response Cell-mediated immunity Cell-mediated immunity is an immune response that does not involve antibodies or complement system but rather involves the activation of macrophages, natural killer cells , antigen-specific cytotoxic T-lymphocytes, and the release of various cytokines in response to an antigen.... , antibody-independent	Contact dermatitis Contact dermatitis Contact dermatitis or Irritant dermatitis is a term for a skin reaction resulting from exposure to allergens or Irritation . Phototoxic dermatitis occurs when the allergen or irritant is activated by sunlight.... Mantoux test Mantoux test The Mantoux test is a diagnostic tool for tuberculosis. It is one of the two major tuberculin skin tests used in the world, largely replacing multiple-puncture tests such as the Tine test.... Chronic transplant rejection Multiple sclerosis Multiple sclerosis Multiple sclerosis is an autoimmune disease in which the immune system attacks the central nervous system, leading to demyelinating disease. Disease onset usually occurs in young adults, and it is more common in females....	T-cells

Type 5

This is an additional type that is sometimes (often in Britain) used as a distinction from Type 2.

Instead of binding to cell surface components, the antibodies recognize and bind to the cell surface receptors

Receptor (biochemistry)

In biochemistry, a receptor is a protein molecule, embedded in either the plasma membrane or cytoplasm of a cell, to which a mobile signaling molecule may attach....
, which either prevents the intended ligand

Ligand

In chemistry, a ligand is either an atom, ion, or molecule that bonds to a central metal, generally involving formal donation of one or more of its electrons....
binding with the receptor or mimics the effects of the ligand, thus impairing cell signaling

Cell signaling

Cell signaling is part of a complex system of communication that governs basic cellular activities and coordinates cell actions. The ability of cells to perceive and correctly respond to their microenvironment is the basis of development, tissue repair, and immunity as well as normal tissue homeostasis....
.

Some clinical examples:

Graves disease
Myasthenia gravis
Myasthenia gravis

Myasthenia gravis is a neuromuscular disease leading to fluctuating muscle weakness and fatigue . It is an autoimmunity, in which weakness is caused by circulating antibody that block acetylcholine receptors at the post-synaptic neuromuscular junction, inhibiting the stimulative effect of the neurotransmitter acetylcholine....

The use of Type 5 is rare. These conditions are more frequently classified as Type 2, though sometimes they are specifically segregated into its own subcategory of Type 2.

Hypersensitivity

Coombs and Gell classification

Type 5

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