Most people know about blood group ABO, with its positives and negatives, but they aren’t the only types. Now, scientists from the University of Bristol and NHS Blood & Transplant have discovered a rare new blood group system, and in the process solved two 30-year-old cases of hemolytic disease on the fetus and newborn.
Your blood type is determined by the presence or absence of proteins known as blood groups that are present on the surface of red blood cells. When a person needs a transfusion, a mismatch of blood types can cause alloimmunization, or the generation of antibodies against the foreign blood group.
Researchers from Bristol’s School of Biochemstry and NHSBT’s International Blood Group Reference Laboratory recently led a study to investigate a 30-year mystery “surrounding the basis of three known, but genetically uncharacterised, antigens that did not fit into any known blood group system,” the university said in a press release.
The scientists investigated people with alloantibodies against a collection of antigens — Era, Erb and Er3. They identified specific changes in the gene coding for the Piezo1 protein, which resulted in production of an altered protein on the cell surface of these individuals.
By using DNA sequencing and gene-editing techniques, the researchers showed that Piezo1 is the carrier for these sites and established Er as a new blood group system.
“This work demonstrates that even after all the research conducted to date, the simple red blood cell can still surprise us,” said Ash Toye, professor of cell biology at the University of Bristol and director of the NIHR Blood and Transplant Research Unit. ”Piezo proteins are mechanosensory proteins that are used by the red cell to sense when its being squeezed. The protein is present at only a few hundred copies in the membrane of each cell. This study really highlights the potential antigenicity of even very lowly expressed proteins and their relevance for transfusion medicine.”
Although two variations within Er group are rare, the group discovered two women whose medical histories they studied lost their babies from hemolytic disease of the fetus and newborn. HDFN is a blood disorder that causes a baby’s red blood cells to break down quickly because of a mismatch with the mother’s red blood cells.
“This discovery solves the 30-year-plus mystery of the genetic background of this blood group system, but the most important consideration for us, in investigating these cases, was to be able to provide answers to two mothers who tragically lost their babies,” said Nicole Thornton, head of Red Cell Reference at the IBGRL. “The more we know about such rare blood group variations, along with the ability to be able to test for and identify them, the better care we are able to offer to such patients in the future.”
The study was published recently in the scientific journal Blood.
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