Rhnull: The ‘Golden Blood’ Type
One of the rarest blood types on Earth.
Sorry AB-negative; you’re not the only rare blood type in the world.
First discovered in an Aboriginal Australian woman in 1961, the Rhnull (Rhesus null) is one of the rarest and most precious blood types in the world. Like a needle in a haystack, less than 50 people in the world are known to have it!
To find out why this blood type was coined as the ‘golden blood’, we need to open the world of blood types and its systems.
The relationship between our immune system and blood types
Blood type (also called blood group) is genetically determined. Blood is primarily categorised based on the presence and/or absence of antigens on the surface of our red blood cells (RBCs). Antigens are distinct molecules or substances capable of coaxing an immune response. Our immune system sends out mini soldiers called antibodies (also known as immunoglobulins), which are special proteins that recognise and bind to these antigens.
If our antibodies recognise these antigens as allies or naturally part of our body, our immune system happily leaves it alone. But if they detect enemy or foreign antigens, our immune system will go on an all-out war to destroy them. Unfortunately, our immune system isn’t perfect. In rare cases, it does attack ‘self’ antigens, as seen in some cases of autoimmune blood disorders.
A, B, O is not easy as 1-2-3 in human-blood transfusion
Now that we know how blood types are determined, you might be wondering “How many blood types are there?”. At present, the International Society of Blood Transfusion recognises 36 human blood group systems and more than 300 different antigens.
You might be familiar with the ABO blood group system. When you ask someone what blood type they are, they might respond with “AB”. They are referring to this most important blood group system in human-blood transfusion. It comprises of only two antigens (antigen A and antigen B), but it can produce these four ABO blood types: A, B, AB or O. This site provides neat animations about the ABO group system and more details of its importance in human-blood transfusions.
ABO blood type by InvictaHOG (Public Domain) on Wikimedia Commons
But there’s another equally significant blood group system to consider in human-blood transfusion: the Rh system (again, Rh pronounced as Rhesus).
Positive or negative, it critically matters
The Rh blood group system has a colourful history. It consists of 61 blood group antigens (Rh antigens), which are expressed as part of a protein complex found only in RBC membranes. Rh antigens are believed to be essential for maintaining the integrity of RBCs.
Briefly going back to ABO blood group system, some people might tell you that they’re “O negative” or “A positive”. The negative/positive part refers to the absence or presence of one Rh antigen: the Rh(D) antigen. It’s the main Rh antigen considered for human-blood transfusion and it’s severely implicated in foetal loss and death of newborn babies.
So… what about Rhnull?
People who have the ‘golden blood’ type lack these Rh antigens. Their DNA lacks the genes responsible for building those RBC protein complexes. These people don’t just lack one, two or three of these 61 Rh antigens, they actually lack all of them. Yes, you read that right: all of them. As you might have guessed, people with Rhnull blood type have abnormal RBCs. They have deformed shapes, leaky membranes and shorter lifespans, which sometimes result in mild anaemia for the individual. Still, the absence of all Rh antigens makes Rhnull the ‘golden blood’, which is highly admired for its rarity and medical purposes.
With great blood type comes great responsibilities (and consequences too!)
Rare blood types within the Rh blood type system can make it difficult or even impossible to get a blood transfusion. This makes Rhnull blood as the ‘universal’ life-saving blood for the Rh blood type system (especially if the donor has an ABO blood type O too). This article follows the story of an individual with this ‘golden blood’ and how it was used to save a life across the world.
But rarity comes at a price. If people with Rhnull blood type requires a blood transfusion, they can only receive Rhnull blood themselves. Even if they receive an O-negative blood, the presence of other Rh antigens on the RBCs may trigger a severe immune response. Therefore, these ‘golden blood’ carriers are solely dependent on other Rhnull donors, but only a few of them regularly donate and they are all spread out across the world.
This is why Rhnull blood is considered as the ‘golden blood’, but it’s not all sunshine and rainbows for those people who carry it. Still, we can’t deny the life-saving properties of this rare blood type and we can deeply appreciate the generosity of those selfless donors.
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