ABO & Carbohydrate Ags Flashcards
ABO, Lewis, H, I and i are all what type of antigens?
Carbohydrate
Carbohydrate antigens are affected by genes that encode for what?
enzymes
Genes for protein antigens encode for what?
Structural proteins
Carbohydrate Vs. Protein Antigens:
-Naturally occuring
Carbohydrate
*Antibodies acquired only after exposure to products containing antigens
Carbohydrate Vs. Protein Antigens:
-Antibody type (IgG/IgM)
Carbohydrate - IgM
Protein - IgG
Carbohydrate Vs. Protein Antigens:
-Temperature
Carbohydrate - RT
Protein - 37 degrees
Carbohydrate Vs. Protein Antigens:
-“agglutinating” vs. “coating”
Carbohydrate - Agglutinating
Protein - Coating
Carbohydrate Vs. Protein Antigens:
- React at AHG phase
- React at IS phase
Protein - AHG phase
Carbohydrate - IS phase
How are H antigens made?
Type 1 and Type 2 precursor carbohydrates by the enzyme products of the:
- H (FUT1) genes
- Se (FUT2) genes
In secretions (saliva, tears) and in plasma, Type __ chains are converted into H antigen by _____ of the ____ gene product.
- Type I
- Fucosylation
- Se (FUT2)
On the surfaces of RBC, Type __ chains are converted into H antigen by _____ of the ____ gene product.
- Type 2
- Fucosylation
- H (FUT1)
Fucosyltransferase 1/2 (FUT1/2) adds _____ to type 1/2 chains at the terminal _______.
- Fucose
- Galatacose
Se (“secretor”) gene (FUT2) frequency.
80%
H gene gene (FUT1) frequency.
virtually 100%
*Bombay = hh
T/F: H antigen is required before A and/or B can be made on RBCs or in Secretions.
True
Lewis antigens are made from type __ precursor by the enzyme product of _____ gene.
- Type I (Secretor)
- Le (FUT3) gene
Secreted Le(b) and Le(c) are receptors for what?
- Norwalk virus
- H. pylori
Le(a) is the epitope for what?
CA19-9
The A & B antigens are made from the __ antigen by the enzyme products of the ___ gene.
- H antigen
- ABO gene
How is the A antigen formed?
- A allele encodes N-acetyl-galactosaminyl transferase
- Adds N-acetyl galactosamine (NAG/Gal-NAc) to H
How is the B antigen formed?
- B allele encodes Galactosyl transferase
- Adds D-galactose (GAL) to H
T/F: The O allele does not encode a functional protein.
True
-Group O RBCs contain abundant unaltered H antigen
The I and i antigens are epitopes within the ___ antigens
ABH
What represent the i antigens?
Unbranched type 1 and 2 oligosaccharides
What represents the I antigens?
Branched type 1 and 2 oligosaccharides
Which antigen (I or i) increases with age?
I (branched oligosaccharides)
*Adults have mostly I antigen
Which antigen (I or i) predominates in neonates and cord blood?
i (Unbranched oligosaccharides)
What situation might cause a resurgence of i?
High red cell turnovers states
Increased postnatal i antigen expression is characteristic of what syndromes? (2)
- Congenital dyserthropoietic anemia (CDA) type II
- Blackfan-Diamond syndrome
As more A or B antigen is made, less H remains.
-Levels of H antigen (decreasing order)
O»A2>B>A2B>A1>A1B
What chromosome are the A, B, and O alleles on?
Chr9 (long arm; q)
When do ABO antigens 1st appear?
What age do they reach adult levels?
- Fetal RBCs at 6 weeks gestation
- age 4
Besides RBCs, where else are ABO antigens expressed? (7)
- Platelets
- Endothelium
- Kidney
- Heart
- Lung
- Bowel
- Pancreas
What antibodies are produced in a person with type O blood? (3)
IgM anti-A and Anti-B
-IgG anti-AB (can cause Mild ABO related HDFN)
What genotypes produce the A blood group?
AA or AO genotype
T/F: A1 cells express more A substance than A2.
True
What percentage of blood group A individuals have the A1 phenotype?
80%
A1 and A2 cells can be distinguished by the strength of reaction with what? (3)
- Anti-A1 reagent (serum of group B)
- Dolichos biflorus lectin (Anti-A1 activity)
- Ulex europaeus (H activity; A2>A1)
What is the most common blood group across all racial lines?
Group O
The B blood group results from which genotypes?
BB or BO genotype
The AB blood group results from what genotype?
AB genotype
How is the Bombay phenotype made?
h gene (an amorph) is inherited instead of H
- No H antigen produced in blood
- Forms anti-H (DANGEROUS)
T/F: The se gene is an amorph.
True
What % of the population are non-secretors?
20% (homozygous for se/se)
What must be present for Le(b) to be made?
Se and Le
T/F: Though Lewis antigen is synthesized on free type I precursor substance, it becomes passively adsorbed onto RBC surfaces.
True
The Lewis type cannot be reliably determined until what age?
2 years old
What is the most common Lewis Phenotype?
Le(a-b+) (both whites and blacks)
What Le phenotype is seen more often in blacks than whites.
Le(a-b-) (blacks 23%; whites 6%)
When are ABO Antibodies first detected?
When do they reach adult titers?
- Infants by 3-6 months
- 2 years old
ABO incompatibility results in what?
Complement activation and BRISK intravascular hemolysis
What group has Lewis antibodies?
Le(a-b-) (exclusively)
-Most commonly Blacks
T/F: Lewis (a-b+) people do NOT make Le(a) antibodies.
True
Lewis Antibodies are nearly always (IgG or IgM).
IgM (Insignificant)
Anti-I antibodies are associated with what type of infection?
Mycoplasma pneumoniae
Anti-i antibodies are associated with what type of infection?
EBV
The rare significant Lewis antibody is always what?
Anti-Le(a)
Why are Lewis antibodies generally insignificant?
- Transfused RBCs shed their Lewis antigens and acquire the Lewis phenotype of the recipient
- Antibodies are quickly absorbed by free serum Lewis antigens
