ABO Group Flashcards
When were the ABO blood groups discovered?
1900; located on chromosome #9
ABO and H genes are ….
glycosyltransferases (enzymes)
- add carbohydrates to type-2 paragloboside chain = Precursor Substance
- made of four sugars attached to ceramide (lipid backbone) which is embedded in the RBC membrane
L-fucosyl transferase
- gene = H
- antigen= H
N-acetyl D galactosaminyl
A
D- galactosyl
B
T or F. Almost 100% of the population will inherit two H genes
T!
as long as one H is inherited, then L-fucosyl transferase will be produced giving rise to an L-fucose being added to the PS
the __ antigen allows for other transferases to add sugars and form A and B antigens
H
antigen structure
glycosphingolipids or glycoproteins
lectins
- proteins (found in nature) that bind specific carbs
- act as artificial Abs that bind certain antigens
Ulex europaeus
- Anti-H
- seeds have lectin that binds H
Secretors
- 80% of population (SeSe, Sese)
- make soluble proteins found in plasma, sweat, tears, etc.
ABO group with most amount of H
O
who produces Anti-H
produced by people who did not inherit at least one H allele
- Bombay blood group
- IgM & naturally occurring
determination of ABO
- forward = testing for ABO involves determination of the antigen on the patient’s cells
- reverse = presence of ABO antibodies in their plasma
Anti-A,B
can be used to check on the forward grouping (newborn)
or help pick up weak subgroups of A or B causing ABO discrepancies
seldom used routinely
What do Bombay people type as?
O
- must be transfused ith Bombay blood due to anti-H
How do we test for Bombay?
- test patient’s red cells with anti-H lectin (Ulex europaeus) => will be 0 because Bombay don’t have H at all
- test for anti-H (which Bombaypeople should have) with O cells which is rich in H => positive!
Subgroups of A
- A1 = 80%
A1A1, A1A2, A1O - A2 = 20%
A2A2, A2O
** no difference in Ags; just clustering that is different **
- A3 = rare; weak in the forward group; 1+ MFA; reverse group is normal
this subgroup of A is a more efficient transferase and puts more terminal sugars on the H antigen
- A1 = one million antigens per RBC
- A2 = 250 000 antigens per RBC
- A3 = 30 000 A antigens per RBC
Anti-A1
- made in response to something else in the environment (naturally occurring)
- cross-reacts with A1
- cold, clinically insignificant IgM (not same properties as anti-A, -B)
- anti-A1 is unexpected; only made by 2-5% of people; <10% of A2B
Dolichus biflorus
anti-A1 lectin
- monoclonal anti-A1
Who makes anti-A1
A2 people and A2B people
T or F. A1 people can make anti-A2, anti-A2B
F!
Other subgroups of A
Ael, Aend, Ax
- small amounts of A or no A antigens on the cell; but have Ag in secretions
