Ahmed Alotaibi: The 49th Human Blood Group System Is Now Recognised
Ahmed Alotaibi, Senior Specialist (Blood bank and blood transfusion) at Afif General Hospital – Riyadh Third Health Cluster (Ministry of Health), shared a post on LinkedIn about a recent article by Tosti J. Mankelow et al., published in JAMA, adding:
“There are now 49 ISBT-recognised human blood group systems.
Meet the newest one: JAMA
A newly published study in Vox Sanguinis describes how an unexplained antibody led to the discovery of an entirely new blood group system.
It started with a woman whose plasma showed a moderate pan-reactive antibody against almost every red cell tested.
Interestingly, her cells and her brother’s cells were non-reactive.
That suggested they were missing an extremely high-prevalence RBC antigen.
Whole-exome sequencing revealed that both siblings were homozygous for an exceptionally rare variant:
F11R c.644G to A, resulting in p.Arg215Gln
F11R encodes Junctional Adhesion Molecule-A (JAM-A).
But finding a mutation was not enough.
Researchers produced both forms of the protein and demonstrated that the patient’s antibody:
Recognised the normal Arg215 JAM-A
Did not recognise the variant Gln215 JAM-A
This confirmed that JAM-A carries a previously unrecognised RBC antigen.
The evidence met ISBT criteria for establishment of a new blood group system.
It is now officially:
ISBT 049: JAMA
Importantly, the patient did not completely lack JAM-A. The amino-acid substitution altered the antigenic epitope recognised by her antibody.
And there is still much we do not know.
The clinical significance of antibodies against the JAMA system, including their ability to cause haemolytic transfusion reactions or HDFN, has not yet been established.
What makes this discovery fascinating is how modern blood-group investigation has evolved:
Serology, followed by family investigation, then genomics, protein expression, and functional confirmation, ultimately leading to the identification of a new blood group system.
A single unexplained antibody can still reveal entirely new biology on the red cell surface.
How many blood group systems are still waiting to be discovered?”
Title: Identification of a novel high-prevalence red blood cell antigen on junctional adhesion molecule-A defines a new blood group system
Authors: Tosti J. Mankelow, Louise A. Tilley, Vanja Karamatic Crew, Benjamin Jones, Marina Izak, Liora Muncher, Vered Yahalom, Nicole M. Thornton
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