Scientists Have Discovered a New Set of Blood Groups


The unborn baby was in trouble. Her mother’s doctors, at a British hospital, knew there was something wrong with the fetus’s blood, so they decided to perform an emergency C-section many weeks before the baby was due. But despite this, and subsequent blood transfusions, the baby suffered a brain haemorrhage with devastating consequences. It has unfortunately passed away.

It was not clear why the bleeding had occurred. But there was a clue in the mother’s blood, where doctors had noticed some strange antibodies. Some time later, when the doctors tried to find out more about her, a sample of the mother’s blood arrived at a laboratory in Bristol, run by researchers who study blood groups.

They made a surprising discovery: the woman’s blood was of an ultra-rare type, which may have made her baby’s blood incompatible with her own. It’s possible that this prompted her immune system to produce antibodies against her baby’s blood—antibodies that then crossed the placenta and harmed her child, ultimately leading to the loss. It may seem unlikely that such a thing could happen, but many decades ago, before doctors had a better understanding of blood types, it was much more common.

By studying the mother’s blood sample, along with a number of others, scientists were able to decipher exactly what made her blood different, and in the process confirmed a new set of blood groupings – the “Er” system, the 44th to describe.

You are probably familiar with the four main blood types – A, B, O and AB. But this is not the only blood classification system. There are many ways to group red blood cells based on differences in the sugars or proteins that coat their surface, known as antigens. The group systems run simultaneously, so your blood can be classified into each – for example, it can be type O in the ABO system, positive (instead of negative) under the Rhesus system, etc.

Due to differences in antigens, if someone receives incompatible blood from a donor, for example, the recipient’s immune system may detect those antigens as foreign and react to them. This can be very dangerous, which is why donated blood must be a suitable match when someone has a transfusion.

On average, one new blood classification system has been described each year by researchers in the past decade. These newer systems tend to involve blood types that are extremely rare, but, for those touched by them, just knowing they have such blood can be life-saving. This is the story of how scientists unraveled the mystery of the last blood system – and why it is so.


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