NHS researchers Blood and Transplant (Bristol), the International Blood Group Reference Laboratory (IBGRL) of the NHSBT and the University of Bristol, in the United Kingdom have identified the genetic background of the blood group antigen AnWj, known for more than 50 years, and have established it as a new system of blood group, called MAL.
Some people may lack this blood group due to a disease, but the rare hereditary form of the AnWj negative phenotype It has only been found in a handful of individualsalthough thanks to this discovery, it will now be easier to find others in the future.
The two most well-known blood group systems are ABO and Rh, but blood is more complex and compatibility between the other groups can save lives.
Within each blood group, red blood cells can carry surface markers called antigens. For example, within the ABO blood group system, there are the A and B antigens: people with A have the A antigen, people with B have the B antigen, people with AB blood have both, and people with O blood have neither.
Currently, there are 47 blood group systems.s recognized that contain more than 360 recognized blood antigens.
This new discovery makes it possible to identify and treat rare patients who lack this blood group. Disorders suppress EVIL and make patients AnWj negative unless they have the rare inherited form (MAL deletion).
People with Hereditary negative AnWj are healthyIf people who are AnWj-negative receive AnWj-positive blood, they may experience a transfusion reaction, and this research allows the development of new genotyping tests to detect these rare individuals and reduce the risk of transfusion-associated complications.
Proof that MAL is responsible for antibody binding AnWj isolated from these rare patients was provided by experiments that showed the appearance of specific reactivity with cells into which the researchers introduced the normal MAL gene, but not the mutant one.
The research team used whole-exome sequencing – the genetic sequencing of all protein-coding DNA – to show that these rare inherited cases were caused by homozygous deletions of the DNA sequence in the MAL gene, which encodes the protein of the same name.
The ‘BAD’ blood type was discovered in 1972
The AnWj antigen – an antigen is a surface marker – It was discovered in 1972, but until now its genetic origin was unknown.
The new research, to be published in Blood, the journal of the American Society of Hematology, and now available online in preprint, establishes a new blood group system (MAL)the 47th to be discovered, as the home of the AnWj antigen.
The team of researchers established that AnWj is transported on the Mal protein. More than 99.9 percent of people are seropositive for AnWj, and these people were shown to express the entire MAL protein in their red blood cells, which did not occur in the cells of AnWj-negative individuals. The team identified homozygous deletions in the MAL gene associated with the AnWj-negative hereditary phenotype.
“The genetic background of AnWj has been a mystery for over 50 years, and I have personally been trying to solve it for almost 20 years of my career. It is a major achievement, and the culmination of long teamwork, to finally establish this new blood group system and be able to offer the best care to rare but important patients,” said Louise Tilley, Senior Research Scientist at the IBGRL Red Cell Reference at NHS Blood and Transplant.
“The work has been difficult because genetic cases are very rare. We would not have succeeded without exome sequencing, as the gene we identified was not an obvious candidate and little is known about the Mal protein in red blood cells.
Demonstrating our findings was a real challenge, and we are grateful for the help of all our collaborators, and of the patients, without whom we would not have reached this point,” he says.
