ABO Blood Group System Flashcards
What are the major blood groups of the ABO system?
A, B, AB, and O
What is the function of blood groups?
- Compatibility testing
- Blood banking
- Ab screening
- Pre-transfusion testing
- Transfusion and transplant therapy
What is the Landsteiner’s law?
#1: If an Ag is present on the RBC surface, the corresponding Ab must be absent in the plasma/serum. #2: If an Ag is absent on the RBC surface, the corresponding Ab must be present in the plasma/serum
What is the Landsteiner’s law?
1: If an Ag is present on the RBC surface, the corresponding Ab must be absent in the plasma/serum.
What is the difference between forward and reverse blood grouping?
- Forward: Use known antibodies to test for antigens on the RBC surface of the patient
- Reverse: Use known antigens to test for antibodies in the plasma/serum of the patient
How are ABO antigens coded for in DNA?
Genes coding for ABO antigens does not code for the antigens as a protein, but do coded for enzymes that will activate a sugar molecule that will attach to an oligosaccharide molecule to form a carbohydrate structure as the antigen.
Explain the biochemistry for the formation of H-antigen.
- Chromosome 19 (H-Locus)
- H-gene form FUT-1
- Fucose bind to oligosaccharide molecule
- H-Antigen (precursor substance)
Explain the biochemistry for the formation of A-antigen.
- Chromosome 9
- Gene expression
- Enzyme: N-Acetyl-D-Galactosaminyl-Transferase
- N-Acetyl-Galactosamine
- A-Antigen
Explain the biochemistry for the formation of B-antigen.
- Chromosome 9
- Gene expression
- Enzyme: D-Galactosaminyl-Transferase
- D-Galactose
- B-Antigen
Explain the biochemistry for the formation of O-antigen.
- Chromosome 9
- Gene expression
- A protein product with no enzymatic activity
- H-Antigen
What is the relationship between H gene and ABO gene?
- H gene forms H-Antigen required for formation of A and/or B antigen coded for by ABO genes
- Inherited in Mendelian fashion
- ABO and H gene expression does not result in direct production of antigens
Where can secretions of ABH substances be found on?
-All tissue cells with the Se gene or Se-antigen
Which blood groups express the most H-antigen in decreasing and increasing order?
Decreasing: O > A2 > A2B > B > A1 > A1B
Increasing: A1B < A1 < B < A2B < A2 < O
What is the difference between secretors and non-secretors?
- Secretors: Individuals w/ soluble ABH antigens in their secretions due to inheritance of the Se-gene (SeSe or Sese)
- Non-secretors: Individuals w/ no A and/or B antigens in their secretions due to no inheritance of the Se-gene (sese)
What is the Bombay and Para-Bombay phenotype?
- Bombay:
- Para-Bombay:
What is the Bombay and Para-Bombay phenotype?
- Bombay: Individuals who inherited the hh-genotype and do not produce the H-antigen, and therefore cannot produce A and /or B antigen. They also lack the Se-gene and does not have ABH antigens in their secretions.
- Para-Bombay: Individuals that did not inherit the H-gene, but did inherit the Se-gene (SeSe or Sese).
Explain the following Bombay paternity cases:
Wife (AO) and Husband (AB) and Affair (OO), Child is OO
The wife and husband both inherited a single dose of the H-gene (Hh) and thechild inherited hh, making him/her unable to produce A and/or B antigen, despite inheriting A or B alleles.
What is a subgroup?
A phenotype with variations in its structure or number of antigens
What are the different subgroups in blood group A and AB?
- A1, A2
- A1B, A2B
How are subgroups identified?
By adsorption and elution techniques to detect antigens on RBC surfaces in the lab
What is a lectin?
Protein with Ab specificity originating from seed extracts of plants
What is the function of a lectin?
Used to distinguish subtypes of various ABO blood groups
What is the AB-trans effect?
Inheriting both AB genes from 1 parent carried on different chromosomes.
What is the AB-cis effect?
Inheriting both AB genes from 1 parent carried on a single chromosome.
What is a high titer?
Ab that can still cause agglutination after the highest dilution.
What is a universal donor?
Individuals who have safe blood which can be transfused into any recipient of the ABO system.
What is a universal recipient?
Individuals that have both A1 and B antigens on their RBC surface and does not have ABO antibodies in their serum and can receive blood from any donor of the ABO system.
What is the clinical significance of ABO in HTR’s?
- Transfusion of A blood into group B patients will be disastrous
- Anti-A in B blood will react with A antigen on the donor RBCs and destroy them and anti-B in A blood will react with B antigen on the recipient RBCs and destroy them, causing activation of intravascular complement
- Lysis and RBC destruction
- HTR: Shock, acute renal failure, DIC, death.
What is the clinical significance of ABO in HDFN’s?
What is the clinical significance of ABO in HDFN’s?
- If a mother is O and is pregnant with a child who is blood group A, the mother will produce IgG anti-B which will cross the placenta and destroy the fetal RBCs.
- This destruction of RBCs result in haemolysis and unconjugated bilirubin to be in the fetal blood stream, which will then lead to kernicterus and brain damage.
- Haemolysis also lead sever anaemia and subsequently to cardiac failure and generalized edema (erythroblastosis faetalis).
