#bloodgroup #blood #malblood
Discovery of a New blood group known as the MAL blood group. What is the MAL blood group?
There are 4 main blood groups (types of blood) – A, B, AB, and O. Your blood group is determined by the genes you inherit from your parents.
Each group can be either RhD+ or RhD-, which means in total there are 8 blood groups.
Antibodies and antigens
Blood is made up of red blood cells, white blood cells and platelets in a liquid called plasma. Your blood group is identified by antibodies and antigens in the blood.
Antibodies are proteins found in plasma. They’re part of your body’s natural defenses. They recognize foreign substances, such as germs, and alert your immune system, which destroys them.
Antigens are protein molecules found on the surface of red blood cells.
The ABO system
There are 4 main blood groups defined by the ABO system:
blood group A – has A antigens on the red blood cells with anti-B antibodies in the plasma
blood group B – has B antigens with anti-A antibodies in the plasma
blood group O – has no antigens, but both anti-A and anti-B antibodies in the plasma
blood group AB – has both A and B antigens, but no antibodies
Blood group O is the most common blood group.
As group O red blood cells do not have any A or B antigens, it can safely be given to any other group.
The discovery of a new blood group, MAL, has solved a 50- year-old mystery. Researchers from NHS Blood and Transplant (Bristol), NHSBT’s International Blood Group Reference Laboratory (IBGRL), and the University of Bristol identified the genetic background of the previously known but mysterious AnWj blood group antigen. The findings allow the identification and treatment of rare patients lacking this blood group.
In most cases, O RhD negative blood (O-) can safely be given to anyone. It’s often used in medical emergencies when the blood type is not immediately known.
It’s safe for most recipients because it does not have any A, B or RhD antigens on the surface of the cells, and is compatible with every other ABO and RhD blood group.
MAL Blood Group
Some people can lack this blood group due to the effect of illness, but the rare inherited form of the AnWj-negative phenotype has only been found in a handful of individuals – though due to this discovery, it will now be easier to find others in the future.
The two best-known blood group systems are ABO and Rh but blood is more complex and matching across the other groups can be lifesaving.
The AnWj antigen – an antigen is a surface marker – was discovered in 1972 but its genetic background was unknown until now. The new research, to be published by Blood, the journal of the American Society of Hematology, and now available online in pre-print, establishes a new blood group system (MAL), the 47th ever to be discovered, as home to the AnWj antigen.
The research team established that AnWj is carried on the Mal protein. More than 99.9% of people are AnWj-positive, and such individuals were shown to express full-length Mal protein on their red cells, which was not present on the cells of AnWj-negative individuals. The team identified homozygous deletions in the MAL gene associated with the inherited AnWj-negative phenotype.
The most common reason for being AnWj-negative is due to suffering from a haematological disorder or some types of cancer which suppress antigen expression (4). Only a very small number of people are AnWj-negative due to a genetic cause. There were five genetically AnWj negative individuals in the study including a family of Arab-Israelis. The blood tested included a sample given by a lady in 2015 who was the first AnWj negative person to be discovered in the 1970s.
Louise Tilley, Senior Research Scientist, IBGRL Red Cell Reference at NHS Blood and Transplant, said: “The genetic background of AnWj has been a mystery for more than 50 years, and one which I personally have been trying to resolve for almost 20 years of my career. It represents a huge achievement, and the culmination of a long team effort, to finally establish this new blood group system and be able to offer the best care to rare, but important, patients.
“The work was difficult because the genetic cases are very rare. We would not have achieved this without exome sequencing, as the gene we identified wasn’t an obvious candidate and little is known about Mal protein in red cells. Proving our findings was challenging, and we appreciate the help of all our collaborators, and the patients, without whom we would not have got to this point.”
Mal is a very small protein with some interesting properties which made it difficult to identify and meant we needed to pursue multiple lines of investigation to accumulate the proof we needed to establish this blood group system.
There are now 47 recognized blood group systems together containing more than 360 recognized blood antigens.
AnWj is named after the first people who made the antibody (Anton and Wj).
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