The MNS antigen system is a

human blood group system The term human blood group systems is defined by the International Society of Blood Transfusion (ISBT) as systems in the human species where cell-surface antigens—in particular, those on blood cells—are "controlled at a single gene locus (gene ...

based upon two genes ( glycophorin A and glycophorin B) on

chromosome 4 Chromosome 4 is one of the 23 pairs of chromosomes in humans. People normally have two copies of this chromosome. Chromosome 4 spans more than 190 million base pairs (the building material of DNA) and represents between 6 and 6.5 percent of the to ...

. There are currently 50

antigens In immunology, an antigen (Ag) is a molecule, moiety, foreign particulate matter, or an allergen, such as pollen, that can bind to a specific antibody or T-cell receptor. The presence of antigens in the body may trigger an immune response. An ...

in the system, but the five most important are called M, N, S, s, and U. The system can be thought of as two separate groups: the M and N

are at one location on the

ECM ECM may refer to the following: Economics and commerce * Engineering change management * Equity capital markets * Error correction model, an econometric model * European Common Market Mathematics * Lenstra's Elliptic curve method for factor ...

and S, s, and U are on a closely related location. The two groups are very closely located together on

and are inherited as a

haplotype A haplotype (haploid genotype) is a group of alleles in an organism that are inherited together from a single parent. Many organisms contain genetic material (DNA) which is inherited from two parents. Normally these organisms have their DNA orga ...

The MN blood group

The MN blood group in humans is under the control of a pair of co-dominant

allele An allele is a variant of the sequence of nucleotides at a particular location, or Locus (genetics), locus, on a DNA molecule. Alleles can differ at a single position through Single-nucleotide polymorphism, single nucleotide polymorphisms (SNP), ...

s, L^M and L^N. Most people in the

Inuit Inuit (singular: Inuk) are a group of culturally and historically similar Indigenous peoples traditionally inhabiting the Arctic and Subarctic regions of North America and Russia, including Greenland, Labrador, Quebec, Nunavut, the Northwe ...

population are M/M, while this genotype is rare among Aborigines. In fact, they tend to possess the opposite genotype (N/N). The MN blood group system is under the control of an

autosomal An autosome is any chromosome that is not a sex chromosome. The members of an autosome pair in a diploid cell have the same morphology, unlike those in allosomal (sex chromosome) pairs, which may have different structures. The DNA in autosome ...

locus found on chromosome 4, with two alleles designated L^M and L^N. The blood type is due to a

glycoprotein Glycoproteins are proteins which contain oligosaccharide (sugar) chains covalently attached to amino acid side-chains. The carbohydrate is attached to the protein in a cotranslational or posttranslational modification. This process is known a ...

present on the surface of a red blood cell (RBC), which behaves as a native

antigen In immunology, an antigen (Ag) is a molecule, moiety, foreign particulate matter, or an allergen, such as pollen, that can bind to a specific antibody or T-cell receptor. The presence of antigens in the body may trigger an immune response. ...

Phenotypic In genetics, the phenotype () is the set of observable characteristics or traits of an organism. The term covers the organism's morphology (physical form and structure), its developmental processes, its biochemical and physiological propert ...

expression at this locus is codominant because an individual may exhibit either one or both antigenic substances. Frequencies of the two

alleles An allele is a variant of the sequence of nucleotides at a particular location, or locus, on a DNA molecule. Alleles can differ at a single position through single nucleotide polymorphisms (SNP), but they can also have insertions and deletions ...

vary widely among human populations.Ralph H. Kathan and Anthony Adamany. 1967. Comparison of Human MM, NN, and MN Blood Group Antigens. The Journal of Biological Chemistry, 242, 1736-1722. M+ and N+ RBCs are common (75% of population) and M+N+ cells are the most common genotype (50% of population). These antigens were an early discovery and are some of the oldest blood antigens known after the ABO system. They were first described by

Karl Landsteiner Karl Landsteiner (; 14 June 1868 – 26 June 1943) was an Austrian-American biologist, physician, and immunologist. He emigrated with his family to New York in 1923 at the age of 55 for professional opportunities, working for the Rockefeller ...

and Philip Levine in 1927. Anti-M and anti-N antibodies are usually

IgM Immunoglobulin M (IgM) is the largest of several isotypes of antibodies (also known as immunoglobulin) that are produced by vertebrates. IgM is the first antibody to appear in the response to initial exposure to an antigen; causing it to also ...

and are rarely associated with

transfusion reactions Blood transfusion is the process of transferring blood products into a person's circulation intravenously. Transfusions are used for various medical conditions to replace lost components of the blood. Early transfusions used whole blood, but ...

. Anti-N is sometimes seen in

dialysis Dialysis may refer to: * Dialysis (chemistry), a process of separating molecules in solution **Electrodialysis, used to transport salt ions from one solution to another through an ion-exchange membrane under the influence of an applied electric po ...

patients due to cross-reactions with the residual

formaldehyde Formaldehyde ( , ) (systematic name methanal) is an organic compound with the chemical formula and structure , more precisely . The compound is a pungent, colourless gas that polymerises spontaneously into paraformaldehyde. It is stored as ...

from sterilizing the equipment. This is usually irrelevant for transfusion since this variant of the antibody does not react at body temperature.

The U and Ss groups: an overview

The S antigen is relatively common (~55% of the population) and the s antigen is very common (~89% of the population). Anti-S and anti-s can cause

hemolytic transfusion reaction An acute hemolytic transfusion reaction (AHTR), also called immediate hemolytic transfusion reaction, is a life-threatening reaction to receiving a blood transfusion. AHTRs occur within 24 hours of the transfusion and can be triggered by a few mill ...

s and

hemolytic disease of the newborn Hemolytic disease of the newborn, also known as hemolytic disease of the fetus and newborn, HDN, HDFN, or erythroblastosis fetalis, is an alloimmune condition that develops in a fetus at or around birth, when the IgG molecules (one of the five ...

.The U antigen is a high incidence antigen, occurring in more than 99.9% of the population. The U was originally short for "Universal", though this is not the case. U negative RBCs can be found in people of

Africa Africa is the world's second-largest and second-most populous continent after Asia. At about 30.3 million km2 (11.7 million square miles) including adjacent islands, it covers 20% of Earth's land area and 6% of its total surfac ...

n descent. This mutation in red cell surface structure also makes the RBCs S- and s-. Anti-U has been associated with both hemolytic transfusion reactions and hemolytic disease of the newborn.

Other MNS antigens

The other 41 identified antigens in the MNS group are low incidence, such as He (0.8% of the population) or high incidence, such as EN^a (>99.9% of the population).

MNS glycoproteins and genes

Antigens of the MNS system are located on one of two glycoproteins: glycophorin A (GPA, CD235A) and glycophorin B (GPB, CD235B).Roback JD et al. AABB Technical Manual, 16th Ed. Bethesda: AABB Press, 2008. Each glycoprotein crosses the membrane once and has an external N-terminal domain (varying in length from 44 amino acids for GPB to 72 amino acids in length for GPA) as well as a C-terminal cytosolic domain (GPB, 8 amino acids in length; GPA, 36 amino acids in length).

MNS antibodies

Serology interpretation of antibody panel for blood group antigens

* MNS antibodies display dosage (they react stronger against cells which are homozygous vs heterozygous for the antigen in question). * Anti-M and anti-N antibodies are naturally occurring, cold-reacting IgM-class antibodies.Mais DD. ASCP Quick Compendium of Clinical Pathology, 2nd Ed. Chicago: ASCP Press, 2009. * Anti-M and anti-N are generally clinically insignificant. * Anti-S, anti-s and anti-U antibodies are acquired following exposure (via pregnancy or past transfusion with blood products) and are warm-reacting IgG-class antibodies. * Anti-S, anti-s and anti-U are usually clinically significant.

References

* https://www.mun.ca/biology/scarr/MN_bloodgroup.html * Mark E. Brecher, Editor (2005), ''AABB Technical Manual'', 15th edition, Bethesda, MD: AABB, , p. 336-340 * Denise M. Harmening (1999), ''Modern Blood Banking and Transfusion Practices'', Philadelphia, PA: F.A. Davis Company, p. 164-169

External links

MNS system
at

BGMUT The BGMUT (Blood Group antigen gene MUTation) Database documents allele, allelic variations in the genes encoding for human blood group systems. It was set up in 1999 through an initiative of the Human Genome Variation Society (HGVS). Since 2006, i ...

Blood Group Antigen Gene Mutation Database,

NCBI The National Center for Biotechnology Information (NCBI) is part of the National Library of Medicine (NLM), a branch of the National Institutes of Health (NIH). It is approved and funded by the government of the United States. The NCBI is loca ...

NIH The National Institutes of Health (NIH) is the primary agency of the United States government responsible for biomedical and public health research. It was founded in 1887 and is part of the United States Department of Health and Human Service ...

{{DEFAULTSORT:Mns Antigen System Blood antigen systems Transfusion medicine