ANTIGENS AND ANTIBODIESDefinition:Blood group systemA series of antigens exhibiting similar serological and physiological characteristics, and inherited according to a specific pattern.Importance of the ABO system:
Indications for ABO grouping:
Indications for ABO grouping:
- Blood Donors-since it can be life threatening to give the wrong ABO group to the patient.
- Transfusion recipients-since we need to know the donor blood is ABO compatible.
- Transplant Candidates and Donors-ABO antigens are found in other tissues as well. Therefore the transplant candidates and donors must be compatible.
- Prenatal Patients-To determine whether the mothers may have babies who are suffering from ABO-HDN. It is also beneficial to know the ABO group should she start hemorrhaging.
- Newborns (sometimes) If the baby is demonstrating symptoms of Hemolytic Disease of the Newborn, the ABO group needs to be determined along with Rh and others.
- Paternity testing Since the inheritance of the ABO Blood Group System is very specific, this serves as one of the first methods to determine the likelihood that the accused father is the father or not.
- A person does not have antibody to his own antigens
- Each person has antibody to the antigen he lacks (only in the ABO system)
- Below are the four blood groups and the antigens and the expected, naturally-occurring antibodies present.
| BLOOD GROUP | ANTIGEN | ANTIBODY |
| A | A | anti-B |
| B | B | anti-A |
| AB | A and B | neither |
| O | neither anti-A or anti-B | anti-A,B |
Most important (clinically significant) Blood Group System for transfusion practice
Why?
This is the only blood group system in which antibodies are consistently, predictably, and naturally present in the serum of people who lack the antigen. Therefore ABO compatibility between donor and recipient is crucial since these strong, naturally occurring A and B antibodies are IgM and can readily activate complement and cause agglutination. If ABO antibodies react with antigens in vivo, result is acute hemolysis and possibly death.
ABO grouping is required for all of the following individuals:
In 1900 Karl Landsteiner reported a series of tests, which identified the ABO Blood Group System. In 1910 he won Nobel prize for medicine for this discovery. He mixed the serum and cells of all the researchers in his lab and found four different patterns of agglutination. From those studies he developed what we now know as Landsteiner's rules for the ABO Blood Group:
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