Although all blood is made of the same basic elements, not all blood is alike. Blood types, which are determined by presence or absence of certain antigens substances that can trigger an immune response if they are foreign to the body. A total of 35 human blood group systems are now recognized by the international society of blood transfusion. The two most important ones are ABO and RhD antigen; they determine someone’s blood type. Almost always an individual has the same blood group for life time, but very rarely an individual’s blood type changes through addition or suppression of an antigen in infection, malignancy, or autoimmune disease.
Another common cause in blood type change is bone marrow transplant. Bone marrow transplants are performed for many leukemia and lymphomas, among other diseases. If a person receives bone marrow from someone who is a different ABO type e.g. A group patient receives O group person bone marrow; the patient’s blood group will eventually convert to the donor’s blood group.
THE ABO BLOOD GROUP SYSTEM
In our blood there are 4 different types of blood groups were determined by the presence or absence of two antigens; antigen A and antigen B on the surface of red blood cells. These antigens may be proteins, carbohydrates, glycoprotein, or glycolipid, depending on the blood group system, and two antibodies A & B. The antigens are present on the red blood cells and the antibodies are present in the serum. The associated anti A and anti B antibodies are usually immunoglobulin M (IgM), antibodies. ABO IgM antibodies are produced in the first years of life by sensitization to environment substances such as food, bacteria and viruses.
- GROUP A: has only the antigen A on red cells and antibody B in the plasma.
- GROUP B: has only the antigen B on red cells and antibody A in the plasma
- GROUP AB: has both A & B antigen on red cells but neither A nor B antibody in the plasma
- GROUP O: has neither A nor B antigens on red cells but both A and B antibody in the plasma.
|ABO BLOOD GROUP||Antigen
For example, people with type B blood will have the B antigen on the surface of their red cells (as shown in the table). As a result, anti-B antibodies will not be produced by them because they would cause the destruction of their own blood. However, if A type blood is injected into their systems, anti-A antibodies in their plasma will recognize it as alien and burst or agglutinate the introduced red cells in order to cleanse the blood of alien protein. AB blood has no antibodies neither anti A nor anti B because they has both antigen if any antibody will produced they will destroyed their own blood cell
Rh BLOOD GROUP SYSTEM
“Rhesus (Rh) factor is an inherited protein found on the surface of red blood cells. If your blood has the protein, you are Rh positive. If your blood lacks the protein, you are Rh negative. Rh positive is common blood type and Rh negative less common”
The Rh blood group system is one of 35 known human blood group system. It is the second most important blood group system, after the ABO blood group system.
Having an Rh negative blood type is not an illness and usually does not affect your health.
Blood typing is a test done to work out which blood type you have, or which blood group you belong to. Not everyone has the same blood group. There are several different blood groups, some of which are more common than others.
People who have matching blood groups are said to be ‘compatible’. This means they could give or receive each other’s blood if necessary.
Combining your ABO blood group with whether you are Rh+ or Rh- means your blood can be classified as one of 8 possible types:
- O positive (O+)
- O negative (O-)
- A positive (A+)
- A negative (A-)
- B positive (B+)
- B negative (B-)
- AB positive (AB+)
- AB negative (AB-)
If a mother is Rh negative but her baby is Rh positive (which can happen if the father is Rh positive), the mother could produce antibodies that fight the baby’s red blood cells. This can happen if blood from the unborn baby enters the mother’s circulation. When there is a risk of this happening (threatened miscarriage, termination, chorionic villus sampling (CVS), abdominal trauma, at delivery), an injection called anti-D can be given to the mother to help prevent these antibodies against Rh positive blood being produced.
SAFE BLOOD TRANSFUSSION
|A+||A+, AB+||O+,O-, A-, A+|
Universal red cell donors
O NEGATIVE :
People with O negative blood don’t have any A, B or Rh antigens on their red blood cells, which means they can donate red blood cells to anyone (their blood cells won’t trigger the recipient’s immune system to “fight” the blood). For this reason, people with O negative blood are referred to as ‘universal donors’.
AB POSITIVE BLOOD GROUP:
People with AB blood group have both A and B antigens on their red blood cells and don’t have antibodies against A or B antigens, which means they can receive red blood cells of any type (their immune system won’t fight them). For this reason, they are referred to as ‘universal recipients.’
Universal plasma donor
AB BLOOD GROUP:
In addition, people who are blood group AB can donate their plasma to anyone (because it doesn’t have any antibodies to other blood groups).
In general, people who are Rh negative should only be given Rh negative blood (as it contains no RhD antigens). If they are given Rh positive blood (which does carry the RhD antigen), their immune system will see it as foreign (non-self) and start producing antibodies against the RhD antigen.
People who are Rh positive can receive either Rh positive or Rh negative blood.
This shows the potential blood types you may inherit.
ABO Inheritance Patterns
|Parent 1||Parent 2||Children may have|
|A||B||A,||B, AB, O|
Note: These are various possible blood groups that children may inherit according to the combination of parental blood group.