Blood is the river of life that courses through our bodies. It is the medium through which nutrients and oxygen are transported to each and every one of the trillions of cells that make the body and waste is directed out. It also functions as the defense mechanism, through antigens present in red and the white blood cells. When its transfusion was first attempted, it was discovered that you cannot randomly transfer blood from one man to another, without checking if their types match. Also, it cannot be manufactured and therefore, patients are dependent on donors for transfusion. According to the Red Cross Society, about 41,000 donations of blood are needed everyday in USA. This article explains why it's important to get your type tested and how it is determined. A ready reference, in the form of a chart has been provided, which indicates transfusion compatibility.
Donate Blood, Donate LifeIn USA, every 2 seconds a blood transfusion is needed. Donating blood at least twice a year can make a world of difference to people in need of your type. Those with rare types like AB Rh- should especially donate regularly.
To understand why there are blood types and how they are classified, one must understand what it is primarily made of. It constitutes three components:
- Red blood cells
- White Blood Cells
The red blood cells primarily decide the type, according to certain inherited substances on their surface, called 'Antibody Generators' or 'Antigens' for short. Antibodies constitute the defense mechanism of the body. They are a sophisticated offensive system, designed to combat pathogens or germs.
Like guided missiles, these antibodies are generated to exterminate specific target pathogens. The type of antigens that occur on your red blood cell's surface are inherited from your mother and father. These antigens have the blueprint for creation of antibodies.
So antigens are important parts of red blood cells and they determine the blood type. These may be carbohydrates, glycoproteins, glycolipids, or carbohydrate coatings on the cells. One can classify blood into different types, based on their presence or absence. There are 30 different blood group systems, based on the occurrence of different antigens.
A complete blood group classification system will have to involve the recognition of about 30 types of antigens on the red blood cells. However, the most widely used classification system is a combination of the ABO and the Rh (Rhesus Factor) systems. Under this system, the type is decided by presence or absence of A-Antigens and B-Antigens, which are most commonly found among the global populace. The Rhesus factor classification system is based on presence or absence of the Rhesus-D antigen. The chart provided here is based on a combined ABO and Rhesus factor system.
Under this system, there are four blood groups, as you can see in the illustration above. They are as follows:
- Type 'A': Red blood cells have the A-antigen, which generates the Anti-B antibodies, that are present in plasma
- Type 'B': Red blood cells have the B-antigen and generate Anti-A antibodies, that are present in the plasma
- Type 'AB': Red Blood cells have both, A-antigen and B-antigen but generate neither Anti-A nor Anti-B antibodies, which are consequently absent in the plasma
- Type 'O': Red Blood cells have neither A-antigen, nor B-antigen, but Anti-A and Anti-B antibodies are present in the plasma
There is one more important antigen on the surface of red blood cells, which also needs to be considered. It is called the Rhesus-D antigen. This antigen mechanism is again inherited from your mother or father. This adds another qualifier to a blood type under the ABO system. A person with any of the four types may be Rhesus D positive (Rh+) or Rhesus D negative (Rh-). That proliferates the number of types to eight (A Rh+, A Rh-, B Rh+, B Rh-, AB Rh+, AB Rh-, O Rh+, O Rh-).
Although, the antigen mechanism is inherited from your father and mother, it lies dormant until there is a need for it to get into action. The anti-A antibodies and Anti B-antibodies are created during the first months after birth, when an infant's gut is infected by bacteria, through food. The Rh-D antibody is generated through placental sensitization (that is when an Rh+ mother exchanges blood with the infant at birth) or through blood transfusion.
The following chart is intended to convey the compatibility issues during blood transfusion. It shows which type of blood can be safely transfused to which other type. That is, it shows which types can be 'donors' to 'recipients', with other blood types. There are three types of blood transfusions that can be made, according to the components that are donated (Red Blood Cells, Plasma, or Whole Blood). The compatibility for all three is different, as shown in the table below. Here, the Rhesus factor is also taken into consideration.
|Recipient's Blood Type||Red Blood Cell Donors||Whole Blood Donors||Plasma Donors|
|O Rh+||O Rh+, O Rh-||O Rh+, O Rh-||Any of types O, A, B, or AB|
|O Rh-||O Rh-||O Rh-||Any of O, A, B or AB|
|A Rh+||A Rh+, A Rh-, O Rh+, O Rh-||A Rh+, A Rh-||Any of types A or AB|
|A Rh-||A Rh-, O Rh-||A Rh-||Any of types A, AB|
|B Rh+||B Rh+, B Rh-, O Rh+, O Rh-||B Rh+, B Rh-||Any of types B or AB|
|B Rh-||B Rh-, O Rh-||B Rh-||Any of types B or AB|
|AB Rh+||A Rh+, A Rh-, B Rh+, B Rh-, AB Rh+, AB Rh-, O Rh+, O Rh-||AB Rh+, AB Rh-||Any of type AB|
|AB Rh-||AB Rh-, A Rh-, B Rh-, O Rh-||AB Rh-||AB|
There are certain rare blood types which have some rare antigens. If you compare their percentage around the world, O Rh+ blood type is the most common and AB Rh- is the rarest. As you can see, in the chart above, AB Rh+ is the universal recipient for red blood cells. O Rh-, although previously considered to be a universal donor of red blood cells, is no longer considered so, due to transfusion compatibility problems. However, it can be still transfused in cases of emergency. AB blood type is the universal plasma donor.
The type of blood group that a person inherits, depends on the types that his or her parents have. Here is a table that identifies the probable group a child could have, based on the types his mother and father possess.
|A||A, O||A, B, AB, O||A, B, AB||A, O|
|B||A, B, AB, O||B, O||A, B, AB||B, O|
|AB||A, B, AB||A, B, AB||A, B, AB||A, B|
|O||A, O||B, O||A, B||O|
Here's an overview of the blood group distributions among the US populace of different ethnicities (Source: Red Cross Society).
|Blood Type||Caucasians||Hispanic||African American||Asian|
A little known fact is that there are more than 600 different types of antigens on the surface of red blood cells, other than A and B. Though the blood group of most people around the world falls in the ABO grouping system, there are some communities that have a unique set of antigens, that are not found anywhere else globally. For example, Duffy-negative and U-negative are two rare blood types found only in the African-American community. Some of the other examples are listed in the table provided below.
|Ethnicity||Rare Blood Group|
|East European/Russian Jews||Dr(a-)|
|Alaskan Native, Native American||RzRz|
|Asian, Pacific Island||Jk (a-b-)|
When a person has blood with rare antigens, there is no option other than finding the right match, if transfusion is needed. Make it a point to donate blood at least once a year, if you happen to belong to a rare blood type. It will go a long way in building up the reserves needed in emergency situations.