haptoglobin

haptoglobin
Identifiers
SymbolHP
Entrez3240
HUGO5141
OMIM140100
RefSeqNM_005143
UniProtP00738
Other data
LocusChr. 16 q22.1
Haptoglobin (abbreviated as Hp) is a protein in the blood plasma that binds free hemoglobin released from erythrocytes with high affinity and thereby inhibits its oxidative activity. The haptoglobin-hemoglobin complex will then be removed by the reticuloendothelial system (mostly the spleen). In clinical settings, the haptoglobin assay is used to screen for and monitor hemolytic anemia

Clinical significance

Since the reticuloendothelial system will remove the haptoglobin-hemoglobin complex from the body, haptoglobin levels will be decreased in hemolytic anaemias. In the process of binding hemoglobin, haptoglobin sequesters the iron within hemoglobin, preventing iron-utilizing bacteria from benefitting from hemolysis. It is theorized that because of this, haptoglobin has evolved into an acute phase protein.

Test order protocol

Haptoglobin is ordered whenever a patient exhibits symptoms of anemia, such as pallor, weakness, orthostatic hypotension (positional changes in blood pressure) or shortness of breath along with physical signs of hemolysis, such as jaundice or dark-colored urine. The test is also commonly ordered as a hemolytic anemia battery which also includes a reticulocyte count and a peripheral blood smear. It can also be ordered along with a Direct Antiglobulin Test when a patient is suspected of having a transfusion reaction. Finally, it may be ordered in conjunction with a bilirubin.

Results interpretation

A decrease in haptoglobin can support a diagnosis of hemolytic anemia, especially when correlated with a decreased RBC count, Hemoglobin, and Hematocrit, and also an increased reticulocyte count.

If the reticulocyte count is increased, but the haptoglobin level is normal, this may indicate that cellular destruction is occurring in the spleen and liver, which may indicate a drug induced hemolysis, or a red cell dysplasia. The spleen and liver recognize an error in the red cells (either Drug coating the red cell membrane, or a dysfunctional red cell membrane), and destroy the cell. This type of destruction does not release hemoglobin into the peripheral blood, so the haptoglobin cannot bind to it. Thus, the haptoglobin will stay normal.

If there are symptoms of anemia but both the reticulocyte count and the haptoglobin level are normal, the anemia is most likely not due to hemolysis, but instead some other error in cellular production, such as aplastic anemia

Haptoglobin levels which are decreased but do not accompany signs of anemia may indicate liver damage, as the liver is not producing enough haptoglobin to begin with.

As haptoglobin is indeed an acute phase protein, any inflammatory process (infection, extreme stress, burns, major crush injury, allergy, etc) may increase the levels of plasma haptoglobin.

Structure

Haptoglobin is produced mostly by hepatocytes but also by other tissues: e.g. skin, lung, and kidney. Haptoglobin, in its simplest form, consists of two α- and two β-chains, connected by disulfide bridges. The chains originate from a common precursor protein which is proteolytically cleaved during protein synthesis.

Hp exists in two allelic forms in the human population, so called Hp1 and Hp2; the latter one having arisen due to the partial duplication of Hp1 gene. Three phenotypes of Hp, therefore are found in humans: Hp1-1, Hp2-1, and Hp2-2. Hp of different phenotypes have been shown to bind hemoglobin with different affinities, with Hp2-2 being the weakest binder.

Miscellaneous Information

Hp has been found in all mammals studied so far, some birds e.g. cormorant and ostrich but also, in its simpler form, in bony fish e.g. zebrafish. Interestingly, Hp is absent in at least some amphibians (Xenopus) and neognathous birds (chicken and goose).

External links

The Entrez Global Query Cross-Database Search System is a powerful federated search engine, or web portal that allows users to search many discrete health sciences databases at the National Center for Biotechnology Information (NCBI) website.
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Hugo is a male given name, a latinized form of the name Hugh, a German/Teutonic name meaning "Bright in Mind and Spirit".

Hugo is one of the most popular names in Europe ranking as high as #2 in France, #6 in Spain, and #7 in Belgium in 2006.
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The National Center for Biotechnology Information (NCBI) is part of the United States National Library of Medicine (NLM), a branch of the National Institutes of Health. The NCBI is located in Bethesda, Maryland and was founded in 1988.
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Swiss-Prot is a manually curated biological database of protein sequences. Swiss-Prot was created in 1986 by Amos Bairoch during his PhD and developed by the Swiss Institute of Bioinformatics and the European Bioinformatics Institute.
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locus (plural loci) is a fixed position on a chromosome, such as the position of a gene or a biomarker (genetic marker). A variant of the DNA sequence at a given locus is called an allele. The ordered list of loci known for a particular genome is called a genetic map.
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Proteins are large organic compounds made of amino acids arranged in a linear chain and joined together by peptide bonds between the carboxyl and amino groups of adjacent amino acid residues.
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Blood plasma is the liquid component of blood, in which the blood cells are suspended. It makes up about 55% of total blood volume. Blood plasma is prepared simply by spinning a tube of fresh blood in a centrifuge until the blood cells fall to the bottom of the tube.
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Hemoglobin, also spelled haemoglobin and abbreviated Hb, is the iron-containing oxygen-transport metalloprotein in the red blood cells of the blood in vertebrates and other animals.
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Red blood cells are the most common type of blood cell and the vertebrate body's principal means of delivering oxygen from the lungs or gills to body tissues via the blood.
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Affinity may refer to:
  • Chemical affinity - the force of attraction between chemical species.
  • Biochemistry, protein-ligand binding affinity
  • Biology, cell affinity refers to how close a cell group tightly to the surrounding cells.

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Redox (shorthand for reduction/oxidation reaction) describes all chemical reactions in which atoms have their oxidation number (oxidation state) changed.

This can be either a simple redox process such as the oxidation of carbon to yield carbon dioxide, or the
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protein complex is a group of two or more associated proteins formed by protein-protein interaction that is stable over time. Protein complexes are a form of quaternary structure.
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The reticuloendothelial system (RES), part of the immune system, consists of the phagocytic cells located in reticular connective tissue, primarily monocytes and macrophages. These cells accumulate in lymph nodes and the spleen.
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The spleen is an organ located in the abdomen of the human body, where it functions in the destruction of old red blood cells and holding a small reservoir of blood. It is regarded as one of the centers of activity of the reticuloendothelial system (part of the immune system).
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Hemolytic anemia
Classification & external resources

ICD-10 D55-D59
ICD-9 282 , 283 , 773

DiseasesDB 5534
MedlinePlus 000571
eMedicine med/979  

Hemolytic anemia
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Hemolytic anemia
Classification & external resources

ICD-10 D55-D59
ICD-9 282 , 283 , 773

DiseasesDB 5534
MedlinePlus 000571
eMedicine med/979  

Hemolytic anemia
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Acute-phase proteins are a class of proteins whose plasma concentrations increase (positive acute phase proteins) or decrease (negative acute phase proteins) in response to inflammation. This response is called the acute-phase reaction (also called acute phase response).
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Anemia
Classification & external resources

ICD-10 D 50. -D 64.
ICD-9 280 - 285

DiseasesDB 663
MedlinePlus 000560
eMedicine med/132   emerg/808 emerg/734
MeSH D000740

Anemia (AmE) or anæmia/anaemia
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Pallor
Classifications and external resources

ICD-10 R 23.1
ICD-9 782.61

Pallor is a reduced amount of oxyhemoglobin in skin or mucous membrane, a pale color which can be caused by illness, emotional shock or stress, avoiding excessive exposure
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Jaundice, NOS
Classification & external resources

Yellowing of the skin and sclera caused by Hepatitis A.
ICD-10 R 17.
ICD-9 782.4

DiseasesDB 7038
MedlinePlus 003243

MeSH D007565

Jaundice, also known as icterus
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Reticulocytes are immature red blood cells, typically composing about 1% of the red cells in the human body. Reticulocytes develop and mature in the red bone marrow and then circulate for about a day in the blood stream before developing into mature red blood cells.
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A blood film or peripheral blood smear is a slide made from a drop of blood, that allows the cells to be examined microscopically. Blood films are usually done to investigate hematological problems (disorders of the blood itself) and, occasionally, to look for
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Coombs test (also known as Coombs' test, antiglobulin test or AGT) refers to two clinical blood tests used in immunohematology and immunology.

The two Coombs tests are:
  • Direct Coombs test (also known as direct antiglobulin test

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In medicine, a transfusion reaction is any adverse event which occurs because of a blood transfusion. These events can take the form of an allergic reaction, a transfusion-related infection, hemolysis related to an incompatible blood type, or an alteration of the immune system
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Bilirubin is a yellow breakdown product of normal heme catabolism. Its levels are elevated in certain diseases and it is responsible for the yellow colour of bruises and the brown colour of feces.
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Hemolytic anemia
Classification & external resources

ICD-10 D55-D59
ICD-9 282 , 283 , 773

DiseasesDB 5534
MedlinePlus 000571
eMedicine med/979  

Hemolytic anemia
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Red blood cells are the most common type of blood cell and the vertebrate body's principal means of delivering oxygen from the lungs or gills to body tissues via the blood.
..... Click the link for more information.
Hemoglobin, also spelled haemoglobin and abbreviated Hb, is the iron-containing oxygen-transport metalloprotein in the red blood cells of the blood in vertebrates and other animals.
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The hematocrit (Ht or HCT) or packed cell volume (PCV) are measures of the proportion of blood volume that is occupied by red blood cells. It is normally 45 ± 7 (38-52%) for males and 42 ± 5 (37-47%) for females.
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The spleen is an organ located in the abdomen of the human body, where it functions in the destruction of old red blood cells and holding a small reservoir of blood. It is regarded as one of the centers of activity of the reticuloendothelial system (part of the immune system).
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