Hypersensitivity
Encyclopedia
Hypersensitivity refers to undesirable reactions produced by the normal immune system, including allergies and autoimmunity
. These reactions may be damaging, uncomfortable, or occasionally fatal. Hypersensitivity reactions require a pre-sensitized (immune) state of the host. The four-group classification was expounded by P. H. G. Gell
and Robin Coombs in 1963.
Instead of binding to cell surface components, the antibodies recognize and bind to the cell surface receptors
, which either prevents the intended ligand
binding with the receptor or mimics the effects of the ligand, thus impairing cell signaling
.
Some clinical examples:
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.
Autoimmunity
Autoimmunity is the failure of an organism to recognize its own constituent parts as self, which allows an immune response against its own cells and tissues. Any disease that results from such an aberrant immune response is termed an autoimmune disease...
. These reactions may be damaging, uncomfortable, or occasionally fatal. 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.-References:...
and Robin Coombs in 1963.
Coombs and Gell classification
| Type | Alternative names | Often mentioned disorders | Mediators |
|---|---|---|---|
| I Type I hypersensitivity Type I hypersensitivity is an allergic reaction provoked by reexposure to a specific type of antigen referred to as an allergen, or to a nonimmunologic stimulus like cold weather or exercise... |
Allergy Allergy An Allergy is a hypersensitivity disorder of the immune system. Allergic reactions occur when a person's immune system reacts to normally harmless substances in the environment. A substance that causes a reaction is called an allergen. These reactions are acquired, predictable, and rapid... (immediate) |
|
Immunoglobulin E Immunoglobulin E is a class of antibody that has been found only in mammals. IgE is a monomeric antibody with 4 Ig-like domains... and IgG4 |
| II Type II hypersensitivity In type II hypersensitivity the antibodies produced by the immune response bind to antigens on the patient's own cell surfaces... |
Cytotoxic, antibody-dependent |
Autoimmune hemolytic anemia Autoimmune hemolytic anemia occurs when antibodies directed against the person's own red blood cells cause the RBCs to burst , leading to insufficient plasma concentration. The lifetime of the RBCs is reduced from the normal 100–120 days to just a few days in serious cases... Thrombocytopenia Thrombocytopenia is a relative decrease of platelets in blood.A normal human platelet count ranges from 150,000 to 450,000 platelets per microliter of blood. These limits are determined by the 2.5th lower and upper percentile, so values outside this range do not necessarily indicate disease... Goodpasture's syndrome Goodpasture’s syndrome is a rare disease characterized by glomerulonephritis and hemorrhaging of the lungs... Graves' disease Graves' disease is an autoimmune disease where the thyroid is overactive, producing an excessive amount of thyroid hormones... *see type V explanation below Myasthenia gravis Myasthenia gravis is an autoimmune neuromuscular disease leading to fluctuating muscle weakness and fatiguability... *see type V explanation below |
Immunoglobulin M Immunoglobulin M, or IgM for short, is a basic antibody that is produced by B cells. It is the primary antibody against A and B antigens on red blood cells. IgM is by far the physically largest antibody in the human circulatory system... or IgG Immunoglobulin G Immunoglobulin G are antibody molecules. Each IgG is composed of four peptide chains — two heavy chains γ and two light chains. Each IgG has two antigen binding sites. Other immunoglobulins may be described in terms of polymers with the IgG structure considered the monomer.IgG constitutes 75%... Complement system The complement system helps or “complements” the ability of antibodies and phagocytic cells to clear pathogens from an organism. It is part of the immune system called the innate immune system that is not adaptable and does not change over the course of an individual's lifetime... ) |
| III Type III hypersensitivity Type III hypersensitivity occurs when antigens and antibodies are present in roughly equal amounts, causing extensive cross-linking.-Presentation:... |
Immune complex Immune complex An immune complex is formed from the integral binding of an antibody to a soluble antigen. The bound antigen acting as a specific epitope, bound to an antibody is referred to as a singular immune complex.... disease |
Rheumatoid arthritis Rheumatoid arthritis is a chronic, systemic inflammatory disorder that may affect many tissues and organs, but principally attacks synovial joints. The process produces an inflammatory response of the synovium secondary to hyperplasia of synovial cells, excess synovial fluid, and the development... Serum sickness Serum sickness in humans is a reaction to proteins in antiserum derived from an non-human animal source. It is a type of hypersensitivity, specifically immune complex hypersensitivity . The term serum sickness–like reaction is occasionally used to refer to similar illnesses that arise from the... 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 vascular walls, serosa , and glomeruli.-History:The Arthus reaction was... Systemic lupus erythematosus Systemic lupus erythematosus , often abbreviated to SLE or lupus, is a systemic autoimmune 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... (SLE Systemic lupus erythematosus Systemic lupus erythematosus , often abbreviated to SLE or lupus, is a systemic autoimmune 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... ) Hypersensitivity pneumonitis Hypersensitivity pneumonitis is an inflammation of the alveoli within the lung caused by hypersensitivity to inhaled organic dusts. Sufferers are commonly exposed to the dust by their occupation or hobbies.-Pathophysiology:Hypersensitivity pneumonitis involves inhalation of an antigen... (Hypersensitivity pneumonitis Hypersensitivity pneumonitis Hypersensitivity pneumonitis is an inflammation of the alveoli within the lung caused by hypersensitivity to inhaled organic dusts. Sufferers are commonly exposed to the dust by their occupation or hobbies.-Pathophysiology:Hypersensitivity pneumonitis involves inhalation of an antigen... ) |
Immunoglobulin G Immunoglobulin G are antibody molecules. Each IgG is composed of four peptide chains — two heavy chains γ and two light chains. Each IgG has two antigen binding sites. Other immunoglobulins may be described in terms of polymers with the IgG structure considered the monomer.IgG constitutes 75%... Complement system The complement system helps or “complements” the ability of antibodies and phagocytic cells to clear pathogens from an organism. It is part of the immune system called the innate immune system that is not adaptable and does not change over the course of an individual's lifetime... ) |
| IV 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 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 is a term for a skin reaction resulting from exposure to allergens or irritants . Phototoxic dermatitis occurs when the allergen or irritant is activated by sunlight.... 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... Multiple sclerosis Multiple sclerosis is an inflammatory disease in which the fatty myelin sheaths around the axons of the brain and spinal cord are damaged, leading to demyelination and scarring as well as a broad spectrum of signs and symptoms... |
|
| V | Autoimmune disease, receptor mediated (see below) |
Graves' disease Graves' disease is an autoimmune disease where the thyroid is overactive, producing an excessive amount of thyroid hormones... Myasthenia gravis Myasthenia gravis is an autoimmune neuromuscular disease leading to fluctuating muscle weakness and fatiguability... |
Immunoglobulin M Immunoglobulin M, or IgM for short, is a basic antibody that is produced by B cells. It is the primary antibody against A and B antigens on red blood cells. IgM is by far the physically largest antibody in the human circulatory system... or IgG Immunoglobulin G Immunoglobulin G are antibody molecules. Each IgG is composed of four peptide chains — two heavy chains γ and two light chains. Each IgG has two antigen binding sites. Other immunoglobulins may be described in terms of polymers with the IgG structure considered the monomer.IgG constitutes 75%... Complement system The complement system helps or “complements” the ability of antibodies and phagocytic cells to clear pathogens from an organism. It is part of the immune system called the innate immune system that is not adaptable and does not change over the course of an individual's lifetime... ) |
Type V
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 molecule found on the surface of a cell, which receives specific chemical signals from neighbouring cells or the wider environment within an organism...
, which either prevents the intended ligand
Ligand
In coordination chemistry, a ligand is an ion or molecule that binds to a central metal atom to form a coordination complex. The bonding between metal and ligand generally involves formal donation of one or more of the ligand's electron pairs. The nature of metal-ligand bonding can range from...
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...
.
Some clinical examples:
- Graves' diseaseGraves' diseaseGraves' disease is an autoimmune disease where the thyroid is overactive, producing an excessive amount of thyroid hormones...
- Myasthenia gravisMyasthenia gravisMyasthenia gravis is an autoimmune neuromuscular disease leading to fluctuating muscle weakness and fatiguability...
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.