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Blood Types – All You Need to Know

The presence or absence of hereditary antigenic compounds and antibodies on the surface of red blood cells is used to classify blood types. Blood is made up of both red and white blood cells. Red blood cells carry oxygen throughout the body while the white blood cells fight infections and platelets that cause blood clots. Antigens can be proteins, carbohydrates, glycolipids, or glycoproteins based on the blood group system. Certain antigens can trigger your immune system to attack the transfused blood as they are foreign to the body. A safe blood transfusion completely depends on careful blood typing and cross-matching. 

There are primarily four blood groups determined by the presence and absence of two antigens, that are, -A and B-. Furthermore, the protein called Rh factor which can either be present or absent, creates eight common blood types, A+, A-, B+, B-, O+, O-, AB+, AB-. 

Let us learn a little more about the common blood groups:

  • Group A: A antigen is present on the red blood cells and B antibody in the plasma.
  • Group B: B antigen is present on the red blood cells and A antibody in the plasma. 
  • Group AB: A and B antigens are present on the red blood cells, and neither A nor B antibodies are present in the plasma.
  • Group O: A and B antigens are absent, but A and B antibodies are present in the plasma. 

How is a Blood Types determined?

Blood types are defined by genes passed down through the generations. One is inherited from the father and another one from the mother to create a pair. There are primarily two ways through which a blood type is determined:

ABO system

If you inherit the A gene from one parent and B from another, your blood type is AB. If you inherit B antigens from both the parents, then your blood type is B. Since blood type O does not contain any antigens, it does not affect A and B blood types. In the case of parents with A and B blood types, the child could still have type O blood if they carry the O gene. Combinations of AA, AB, BB, AO, BO, OO are called genotypes, and A, B, AB, and O blood types stem from these genotypes. 

Rh factor

The antigen Rh is found on red blood cells. The presence of it would mean you are Rh-positive, and the absence would be considered as Rh-negative. Depending on the presence of the Rh antigen, the blood type is assigned a positive (+) or a negative (-) symbol. 

What are rare blood types and transfusions?

There are over 600 known antigens, and its presence and absence create rare blood types.  A blood type is rare if the patient lacks 99% of the antigens people are positive for. From the point of transfusion, a rare blood type lacks a high-frequency blood group antigen and multiple common antigens. Blood donations of such kind help in the transfusion to the recipients with all antibodies to the corresponding antigens.

There are specific ways for blood types to be matched for a safe transfusion. Rh-negative blood is given to Rh-negative patients, whereas Rh-positive blood and Rh-negative blood can be given to Rh-positive patients. However, patients with Rh-negative blood carrying an Rh-positive child can cause a dangerous condition called Rh incompatibility. Furthermore, certain blood groups are unique to specific ethnic and racial groups. 

Is O negative Rare Blood Type?

The universal red cell donor is type O negative blood, and the universal plasma donor is type AB blood. O- blood can be used in transfusions of any blood type and is thus, short in supply with high demand in hospitals. It is the preferred blood type for emergency transfusions and for immune-deficient infants. 

Rare blood donors are present in less than 1/1000 people. Being a rare blood donor means that your blood is missing one common antigen or combination of antigens. AB- is a rare blood type, and the demand for it is, however, low. 

Blood subtype is present in everyone and is important for regular transfusions. Ro subtype, a variation of Rh-positive blood type, is a rare blood type that is demand. It is used to treat people with sickle cell, a hereditary blood disorder that causes the red blood cells to become half-moon shaped. This commonly affects people from African or Caribbean backgrounds. 

What is the golden blood type?

Golden blood type or Rh-null blood group is the rarest blood group globally and contains no Rh antigens on the red blood cells. DNAs of people with Rh-null blood group lack genes responsible for building red blood cell protein complexes. Donations of Rh-null are difficult to obtain as only less than 50 individuals has this blood type, thus making it a precious blood group. People with the golden blood type may have deformed shapes and suffer from shorter life spans, resulting in mild anemia in certain cases. Blood transfusion for people with Rh-null is highly difficult as they can only receive Rh-null blood. However, they are the universal donor for the Rh blood type system. 

How does Blood Types matter?

The antibodies present in your immune system help fight off unrecognized materials such as viruses and bacteria. Sometimes, antibodies attack antigens that are not in your natural blood type. For example, during a transfusion, if B blood mixes with A blood, the antibodies will destroy the A antigens, resulting in life-threatening problems. Blood types don’t have to be exact matches all the time. A person with AB blood type can receive either type A or type B blood. Since type O blood does not contain any antigens, it is the universal blood donor. However, patients with type O can only receive type O blood

Even though we are only familiar with ABO and Rh systems, there are over 30 blood typing systems. Blood transfusion is needed for women with complications in pregnancy, people suffering from severe trauma and many more. If you can help others in need, do donate your blood and save lives!

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