A, B, and H Flashcards
What is a blood group system?
Series of allelic genes and their modifiers
may be 2 or many alleles
Produce chemical related but serologically distinct antigens
Antibody is how the antigen is recognized and antigen is defined by antibody
Red cell antigens are?
chemical structures embedded or protruding from the RBC membrane
May be a soluble substance
genotype determines the presence or absence of antigens
Where are ABO antigens found in blood?
RBC’s, Plt’s, lymphocytes, and circulating proteins
Where are ABO antigens found in the body
Kidney, heart, lungs, liver, pancrease, gastric mucosa, and endothelium
Where are ABO antigens found in secretors?
glands, goblet cells, tears, urine, saliva, digestive juices, milk, sweat, bile, pericardial fluid, and peritoneal fluid
What chromosome in h gene located on?
What enzyme does H code for?
19
FUT1
What does FUT1 do?
Fucosyl transferase
adds L-fucose to terminal sugar on type 2 chain
a1-2 linkage
Gluc>Gal>GlcNAN>(1-4)Gal >(1-2) Fuc
What chromosome are ABO genes on?
Chromosome 9
What does A gene code for?
N-acetylgalactosamyl transferase
add GalNAc to Gal of H chain in a1-3 linkage
What does B gene code for?
D-galactose transferase
adds D-galactose to Gal of H chain in a1-3 chain
What causes O phenotype?
O gene codes for non-functional transferase
O01 and O02 caused by a deletion and framshift leading to truncated protein
AA critical in determining A and B genes?
Gly235Ser, Leu266Met, Gly268Ala
What type of chains are ABO antigens carried on?
A and B antigens are a terminal sugar attached to oliosaccharide chain carried on glycoproteins 90% and glycosphingolipids 10%
ABH antigens on glycoproteins are on what kind of chain
ABH antigens are mainly on N-GLycans containing polyactosaminyl units on Band 3 (DI), the glucose transport protein, RhAG, and CHIP-1 (CO)
What gestational age is ABO antigen detected?
5-6 weeks
What age are ABO antigens full formed?
By 2-4 years of age
What race has a stronger B antigens
Blacks, also have 20% Group B
Most to least H antigen
O > A2 > A2B > B > A1 > A1B
What is classic Bombay?
hh, sese, = Lea on RBC if Le gene present
Types as Group O, ABS pan-reactive and AC negative
Patient is negative with anti-H and AB is non-reactive with Oh cells
Allo Anti-H
Anti-H in bombay is very potent
Predominatly IgM that reacts at 4-37C
Often stronger at IS then AHG phase
What disease is also produces Oh phenotype?
LAD - Leukocyte adhesion deficiency also produces Oh cells due to deficiency in GDP-fucose transporter
What is gene epitasis?
where gene masks expresssion of another gene
Epistatic reactions occur because to transferase are required
Ex) H is required for A and B production
What is Para-Bombay?
hh, Se gene present
A, B, H in secretions and can adsorb onto RBC’s
Serum may still have weak anti-H or -IH and may be clinically significant
Anti-A1 may present because less A antigen present
May need adsorption/elution to detect antigens
What is auto-H?
cold agglutin may be seen with anti-I More common in group A or AB people = less H IgM antibody that reacts at RT or lower Not clinically significant
What is CIS AB?
non-mendelian inheritance
1 gene produces mutant enzyme that makes both A and B transferase
Cis AB/O, Cis, AB/A, Cis, CisAB/B
What blood group is gastric cancer more common?
Group A
What blood group is gastric and duodenal ulcers more common in?
Group O
Group O and coag factors
Group O has 25% less VIII and vWf?
May tend to bleed more
Characteristics of ABO antibodies
IgM, reactive at RT
binds complement
Group O has anti-A,B - recognizes a shared determinant
What age are ABO antibodies formed?
Antibodies can be seen at 3 months
1 year everyone should have antibodies
by 5-10 years antibodies will be at adult levels
What does Se gene do?
Se gene, FUT2, add a fucose to type 1 chains
fucose is added to terminal galactose in -2 linkage
H substance in secretions
Type 1 chains
Terminal galactose attached in 1-3 linkage
present in secretions/ adsorbed onto membrane
attached to protein
first sugar is GalNAc
Type 2 chains
terminal galactose attached to GlcNAc in 1-4 linkage
present on RBC’s
attached to lipid (ceramide or glycospingolipid)
First sugar is glucose
Anti-A1 lectin - Diluted
Dolichos biflorus Diluted
reacts with only A1 cells
also aglutinates strong Sda pos cells and Tn polyagglutinable regardless of ABO type
Anti-A lectin - Undiltuted
Dolichos biflorus undiluted
reacts with any group A
Anti-B lectin
Griffonia simplicifolia (aged)
may also be found as GS II + GalNAc
Used to detect acquired B -
Anti-A + B lectin
Griffonia simplicifolia (fresh)
has weak anti-A activity
detects A and B activity
Anti-H
Ulex europeaus
What causes ABO subgroups?
AA substitution, resulting from a mutation, deletion, or gene recombination, within exon 6 and 7
less efficient transferase = weaker serological reactions
A2 subgroup
20% of group A are A2
A2 is same transferase as A1 but less efficient
A1 vs A2 phenotype
A1 converts nearly all H substances to A >1,000,000
A2 converts only 1/4 of H substance 200,000
A1 is on branched chains (H3 and H4)
A2 is on unbranched chains (H1 and H2)
Why do A subgroups make Anti-A1?
Anti-A1 is really antibody against branched chains
Anti-A(cd)
AsubB have less A(cd) so more likely to make Anti-A1
A2 = 1-8%
A2B = 20-30%
A3
mixed field agglutination
Anti-A1 may be present
Ax
not agglutinated by Anti-A but sometimes weak with Anti-A,B human sera
most monoclonal reagents detect
similar to Am except A substance not in secretions
Ax has substance that is only detected using Ax cells
Anti-A can be adsorbed and eluted off
Aend
MF agglutination but very weak
only 10% of cells agglutination
No A substance in secretions
Anti-A1 usually present
Am
Weak or negative with Anti-A or Anti-A,b
Adsorption/elution required
Usually do not produce Anti-A1
Looks like Ax but Am has A substance in secretions
Ael
usually so weak antigens not detected
may have weak reaction with anti-A,B
Usually has Anti-A1 present which make person look like a group O
no A substance in secretions
need adsorption/elution to detect A antigen
Advantages of monoclonal reagents
Detection of Ax phenotype
fewer false positive due to anti-T, anti-Tk, anti-Tm
most will not detect acquired B (except MH04)
Causes of Missing reactions in forward type
Neutralization of Anti-A/B with high A/B substance Massive transfusion of Group O BMT Large fetomaternal bleed True chimerism Disease (AML, Leukemia, Hodgkin's)
Describe neutralization of Anti-A or Anti-B
Occurs with plasma suspended cells in patients with carcinoma of stomach or pancreas. Patients have an increased A or B substance that binds to Anti-A or -B reagent making antibody unable to bind to patient RBC ag
What is adsorption/elution?
Incubate cells w/ Anti-A from human sera if possible for 30-60 min
Lui freeze thaw to elute antibody bound to cells
test Eluate with A1, A2, O cells.
If A antigen present, A cells will react because Anti-A will be present in Eluate
What is B(A)?
Autosomal dominate phenotype (BB)
Weak expression of A antigen is due to an elevated D-galactosyl transferase that transfers a small amt of GalNAc = A
Agglutination is weak and easily dispersed
Only MH04 detects it
rare (1 in 1000 group B)
2+ with Anti-A 4+ with anti-B and strong 4+ with A Cells
What is A(B)?
Associated with elevated H antigen and plasma H-transferase
increased H precursor allows for synthesis of B antigen by A antigen
Be described with monoclonal B reagent
Causes of extra reactions in forward type
Acquired B Polyagglutination BMT Antibody coated cells Rouleaux
What is Acquired B?
Strong reaction with Anti-A but weak reaction with Anti-B
Seen with infected bowel
Bacterial enzymes remove an acetyl group from GalNAc > resembles galactose = B antigen
Not seen with monoclonal reagents
lower pH to 6.0 of human anti-B
GS I +GalNAc lectin (aged) will reacts with true B antigen
What is polyagglutination?
A cell problem where crypt antigens (T, Tn) that are normally masked are exposed by disease such as sepsis or bowel infection
Crypt antigens react with Anti-T and Anti-Tn that are present in normal human sera. = Avoid plasma TRN
Persons wtih polyagglutination lack Anti-T, Tn
What is Tn polyagglutination?
Only seen in Group O or B
Sialic acid residues on glycophorin A and B give RBC net negative charge
Mutation on X chromosome leads to decreased synthesis of Sialic residues exposing crypt antigens that resembles A antigen.
Reacts strongly with A1 lectin but should not react with monoclonal Anti-A. Seen using human polyclonal antisera.
Enzyme treat cells to remove M and N antigen
What is cis A/B
Appear as A2. A antigen is more than A2 but less than A1. B antigen is weakly expressed with Anti-B present
Secretors have normal A, Large amt H, and weak B
High levels of H antigen cells
Mutated enzyme is capable of producing A and B
Resolve antibody coated cells interfering with ABO
IgM antibodies can be washed away with warm saline or DTT treatment
IgG antibodies treat with EGA = EDTA glycine-acid
What causes rouleaux?
Abnormal proteins in the plasma seen in MM, cryoglobulinemia, macroglobulinemia
Causes of weak reactions in back typing
Decreased antibodies due to age
Hypo or agammaglobuliemia
Disease (Lymphomas, Waldenstrom’s marcroglobuliemia, CLL, Immusuppressive, and Immudeficiency)
Causes of extra reactions in back typing
Rouleaux
Cold antibodies (Anti-A1, IgM, or cold auto)
Antibodies to media in reagent red cells
Passively acquired allo antibodies (IVIG, PLT’s, Many Group O RBC’s)
Cold autoadsorption procedure
Treat patient RBC’s with ficin or ZZAP to remove antibody.
Mix 1 mL of patient’s ficin cells with 1 mL of serum at 4C for 30 min
Centrifuge and transfer adsorbed serum to a clean test tube to repeat testing with fresh ficin treated cells
B3 phenotype
MF reactivity with B substance in secretions
Bm
Weak B with B substance in secretions
Bx
Weak or negative reaction with anti-B
May have very weak Anit-B present in serum
Bel
Weak or negative reaction with Anti-B
requires adsorption/elution to detect
May have weak anti-B present in serum
