Secretor status

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Secretor status refers to the presence or absence of water-soluble ABO blood group antigens in a person's bodily fluids, such as saliva, tears, breast milk, urine, and semen. People who secrete these antigens in their bodily fluids are referred to as secretors, while people who do not are termed non-secretors. Secretor status is controlled by the FUT2 gene (also called the Se gene), and the secretor phenotype is inherited in an autosomal dominant manner, being expressed by individuals who have at least one functioning copy of the gene. The non-secretor phenotype (se) is a recessive trait. [1] : 125–7  Approximately 80% of Caucasian people are secretors, while 20% are non-secretors. Non-secretors have reduced susceptibility to the most common strains of norovirus. [2] Expression of the antigens in the Lewis blood group is also affected by secretor status: non-secretors cannot produce the Le(b) antigen. [3] : 190 

Contents

Genetics

The expression of ABO blood group antigens is determined by the interaction of three genes: the ABO gene, which controls expression of the A and B antigens; the FUT1 or H gene, which controls expression of the H antigen, the precursor of ABO antigens; and the secretor gene, FUT2 or Se. All of these genes encode glycosyltransferases, which are enzymes that add sugars to precursor substances to create new substances. [1] : 123 

The H antigen is required for ABO blood group antigens to be formed. [note 1] The Se gene, which encodes the enzyme α-2-L-fucosyltransferase, controls the formation of H antigen in bodily secretions. In people with the secretor genotype, the enzyme converts a precursor substance found in body fluids to the H antigen, which is then modified by the glycosyltransferases encoded by the ABO gene to produce the antigens corresponding to the person's ABO blood type. Because non-secretors cannot form H antigen in body fluids, they cannot express soluble ABO antigens. [1] : 124–6 

Lewis blood group phenotypes are controlled by the FUT3 or Le gene and the Se gene. There are two major antigens in the Lewis system: Le(a) and Le(b). Individuals who are negative for Le express neither antigen and their blood type is designated as Le(a-b-). In individuals who are positive for Le, the blood type is determined by the person's secretor status. The Le gene encodes a glycosyltransferase that produces the Le(a) antigen from a precursor substance. In secretors, α-2-L-fucosyltransferase modifies this precursor substance, which causes it to form Le(b) when acted on by the enzyme encoded by the Le gene. Thus, secretors who are positive for Le express the Le(a-b+) type, while non-secretors who are positive for Le express the Le(a+b-) blood type. [note 2] [1] : 178–81  [3] : 196 

Clinical significance

Noroviruses bind to secreted blood group antigens on the mucosa of the digestive tract. [4] : 537  Because non-secretors do not express these antigens, they exhibit decreased susceptibility to most strains of the disease. [2]

Secretor status can be determined through genotyping or through serologic methods. In the serologic method, the person's saliva is boiled, then added to reagents containing antibodies against the A, B, and H antigens. Red blood cells expressing these antigens are then added to the saliva-reagent mixtures. If the person is a secretor, the antibodies will bind to the antigens in their saliva rather than the red blood cells, and will not cause red blood cells to agglutinate. [5] : 25 

Secretor status testing was historically used in forensic science, but this has been made obsolete by advances in DNA testing. [6] : 226 

Prevalence

Approximately 80% of Caucasian people possess the Se gene and are secretors; the other 20% are non-secretors. [2] The frequency of the Se gene is approximately 50% in most ethnic groups, but Aboriginal Australians, Inuit, and some Native American and Melanesian groups exhibit a frequency of nearly 100%, while the frequency is only 22% in South India. [5] : 25 

Notes

  1. ↑ Individuals who are negative for the H gene express the rare Bombay blood type. [1] : 124–6 
  2. ↑ A weak variant of the Se gene found mainly in Asian populations results in a Le(a+b+) blood type. [1] : 181 

Related Research Articles

Dominance (genetics) One gene variant masking the effect of another in the other copy of the gene

In genetics, dominance is the phenomenon of one variant (allele) of a gene on a chromosome masking or overriding the effect of a different variant of the same gene on the other copy of the chromosome. The first variant is termed dominant and the second recessive. This state of having two different variants of the same gene on each chromosome is originally caused by a mutation in one of the genes, either new or inherited. The terms autosomal dominant or autosomal recessive are used to describe gene variants on non-sex chromosomes (autosomes) and their associated traits, while those on sex chromosomes (allosomes) are termed X-linked dominant, X-linked recessive or Y-linked; these have an inheritance and presentation pattern that depends on the sex of both the parent and the child. Since there is only one copy of the Y chromosome, Y-linked traits cannot be dominant nor recessive. Additionally, there are other forms of dominance such as incomplete dominance, in which a gene variant has a partial effect compared to when it is present on both chromosomes, and co-dominance, in which different variants on each chromosome both show their associated traits.

ABO blood group system Classification of blood types

The ABO blood group system is used to denote the presence of one, both, or neither of the A and B antigens on erythrocytes. In human blood transfusions it is the most important of the 38 different blood type classification systems currently recognized. A mismatch in this, or any other serotype, can cause a potentially fatal adverse reaction after a transfusion, or an unwanted immune response to an organ transplant. The associated anti-A and anti-B antibodies are usually IgM antibodies, produced in the first years of life by sensitization to environmental substances such as food, bacteria, and viruses.

Chromosome 19 human chromosome

Chromosome 19 is one of the 23 pairs of chromosomes in humans. People normally have two copies of this chromosome. Chromosome 19 spans more than 58.6 million base pairs, the building material of DNA.

A fucosyltransferase is an enzyme that transfers an L-fucose sugar from a GDP-fucose donor substrate to an acceptor substrate. The acceptor substrate can be another sugar such as the transfer of a fucose to a core GlcNAc (N-acetylglucosamine) sugar as in the case of N-linked glycosylation, or to a protein, as in the case of O-linked glycosylation produced by O-fucosyltransferase. There are various fucosyltransferases in mammals, the vast majority of which, are located in the Golgi apparatus. The O-fucosyltransferases have recently been shown to localize to the endoplasmic reticulum (ER).

Glycosyltransferase Class of enzymes that catalyze the transfer of glycosyl groups to an acceptor

Glycosyltransferases are enzymes that establish natural glycosidic linkages. They catalyze the transfer of saccharide moieties from an activated nucleotide sugar to a nucleophilic glycosyl acceptor molecule, the nucleophile of which can be oxygen- carbon-, nitrogen-, or sulfur-based.

hh, or the Bombay blood group, is a rare blood type. This blood phenotype was first discovered in Bombay by Dr. Y. M. Bhende in 1952. It is mostly found in the Indian sub-continent and parts of the Middle East such as Iran.

The Lewis antigen system is a human blood group system. It is based upon two genes on chromosome 19: FUT3, or Lewis gene; and FUT2, or Secretor gene. Both genes are expressed in glandular epithelia. FUT2 has a dominant allele which codes for an enzyme and a recessive allele which does not produce a functional enzyme. Similarly, FUT3 has a functional dominant allele (Le) and a non-functional recessive allele (le).

Ii antigen system Human blood group system

The Ii antigen system is a human blood group system based upon a gene on chromosome 6 and consisting of the I antigen and the i antigen. The I antigen is normally present on the cell membrane of red blood cells in all adults, while the i antigen is present in fetuses and newborns.

H antigen can refer to one of various types of antigens having diverse biological functions. H antigen is located on the 19th chromosome in humans, and has a variety of functions and definitions as follows:

In enzymology, a 3-galactosyl-N-acetylglucosaminide 4-alpha-L-fucosyltransferase is an enzyme that catalyzes the chemical reaction

In enzymology, a galactoside 2-alpha-L-fucosyltransferase is an enzyme that catalyzes the chemical reaction

Fucosyltransferase 3

Galactoside 3(4)-L-fucosyltransferase is an enzyme that in humans is encoded by the FUT3 gene.

FUT2 Protein-coding gene in humans

Galactoside 2-alpha-L-fucosyltransferase 2 is an enzyme that in humans is encoded by the FUT2 gene. It affects the secretor status of ABO antigens.

FUT1

Galactoside 2-alpha-L-fucosyltransferase 1 is an enzyme that in humans is encoded by the FUT1 gene.

FUT6

Alpha-(1,3)-fucosyltransferase is an enzyme that in humans is encoded by the FUT6 gene.

FUT9

Alpha-(1,3)-fucosyltransferase is an enzyme that in humans is encoded by the FUT9 gene.

ABO (gene) Protein-coding gene in the species Homo sapiens

Histo-blood group ABO system transferase is an enzyme with glycosyltransferase activity, which is encoded by the ABO gene in humans. It is ubiquitously expressed in many tissues and cell types. ABO determines the ABO blood group of an individual by modifying the oligosaccharides on cell surface glycoproteins. Variations in the sequence of the protein between individuals determine the type of modification and the blood group. The ABO gene also contains one of 27 SNPs associated with increased risk of coronary artery disease.

Fucosyltransferase 4 , also known as FUT4, is an enzyme which in humans is encoded by the FUT4 gene.

Cis AB is a type of rare mutation in the ABO gene. It happens when the transferase allele contains a mix of amino acids from either A or B alleles, producing a bifunctional enzyme that can produce both types of antigens, usually with one weaker than the other. This results in a serum test result much like the standard, separate (trans) AB phenotype, although the weaker antigen can occasionally fail to be detected. It complicates the basic inheritance pattern and blood-transfusion compatibility matching for ABO blood typing.

The Sid blood group system is a human blood group defined by the presence or absence of the Sd(a) antigen on a person's red blood cells. About 96% of people are positive for the Sd(a) antigen, which is inherited as a dominant trait. Among Sd(a) positive individuals, the expression of the antigen ranges from extremely weak to extremely strong. Very strong expression of the antigen is referred to as a Sd(a++) phenotype. In addition to being expressed on red blood cells, Sd(a) is secreted in bodily fluids such as saliva and breast milk, and is found in the highest concentrations in urine. Urine testing is considered the most reliable method for determining a person's Sid blood type.

References

  1. 1 2 3 4 5 6 Denise M Harmening (30 November 2018). Modern Blood Banking & Transfusion Practices. F.A. Davis. ISBN   978-0-8036-9462-0.
  2. 1 2 3 Rydell GE, Kindberg E, Larson G, Svensson L (November 2011). "Susceptibility to winter vomiting disease: A sweet matter". Rev. Med. Virol. 21 (6): 370–382. doi:10.1002/rmv.704. PMID   22025362. S2CID   6679013.
  3. 1 2 Jeffrey McCullough (27 September 2016). Transfusion Medicine. Wiley. ISBN   978-1-119-23652-8.
  4. ↑ Karen C. Carroll; Janet S. Butel; Stephen A. Morse (12 August 2015). Jawetz Melnick & Adelbergs Medical Microbiology (27 ed.). McGraw-Hill Education. ISBN   978-0-07-182503-0.
  5. 1 2 Geoff Daniels (16 January 2013). Human Blood Groups. John Wiley & Sons. ISBN   978-1-118-49354-0.
  6. ↑ Suzanne Bell (2009). The Facts on File Dictionary of Forensic Science. Infobase Publishing. ISBN   978-1-4381-0944-2.
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