A research team led by scientists from the British National Health Service’s Blood and Transplant Group (NHS Blood and Transplant), in collaboration with a group from the University of Bristol, has discovered a new blood group, called MAL.
Although the best-known blood groups are those that form the AB0 and Rh system, in their eight possible combinations there are a total of 47 different blood groups, including MAL. The specific discovery, already published in the journal Bloodconsists of identifying the genetic origin of the AnWj antigen, and will allow the identification and treatment of the few people who are devoid of it. With this discovery, a mystery 50 years, the time that has elapsed since the discovery of the AnWj antigen in 1972 and the identification today of its genetic origin, and therefore of the new group.
“If AnWj-negative individuals receive AnWj-positive blood, they could suffer a transfusion reaction, and this research enables the development of new genotyping tests to detect these rare individuals and reduce the risk of transfusion-associated complications,” the University of Bristol said in a note.
The research team found that 99.9% of AnWj-positive individuals had the full MAL protein in their red blood cells, but it was not present in the cells of AnWj-negative individuals.
The most common reason for being AnWj negative is having a blood disorder or certain types of cancer that suppress the expression of the antigen. Only a very small number of people are AnWj negative due to a genetic cause. In the study, there were five people who were genetically negative for AnWj. The blood tested included a sample donated by a woman in 2015, who was the first AnWj negative person discovered in the 1970s.
“The genetic makeup of AnWj has been a mystery for over 50 years, and one that I have personally spent nearly 20 years of my career trying to solve. It is a great achievement, and the culmination of a long team effort, to finally establish this new blood group system and be able to provide the best care for rare but important patients,” Louise Tilley, Senior Research Scientist at the IBGRL Cell Reference Network, told NHS Blood and Transplant.
“The work was difficult because genetic cases are very rare. We would not have achieved this without exome sequencing, because the gene we identified was not an obvious candidate and little is known about the Mal protein present in red blood cells,” according to the University of Bristol note.
“It is very exciting that we have been able to use our ability to manipulate gene expression in developing blood cells to help confirm the identity of the AnWj blood group, which has been an exceptional enigma for half a century,” added his colleague Ash Toye, Professor of Cell Biology in the School of Biochemistry and Director of the NIHR Blood and Transplant Research Unit in RBC Products at the University of Bristol. “This advance will help identify these rare donors and help patients in the future,” he said.
