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A, B, and H Flashcards

1
Q

What is a blood group system?

A

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

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2
Q

Red cell antigens are?

A

chemical structures embedded or protruding from the RBC membrane
May be a soluble substance
genotype determines the presence or absence of antigens

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3
Q

Where are ABO antigens found in blood?

A

RBC’s, Plt’s, lymphocytes, and circulating proteins

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4
Q

Where are ABO antigens found in the body

A

Kidney, heart, lungs, liver, pancrease, gastric mucosa, and endothelium

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5
Q

Where are ABO antigens found in secretors?

A

glands, goblet cells, tears, urine, saliva, digestive juices, milk, sweat, bile, pericardial fluid, and peritoneal fluid

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6
Q

What chromosome in h gene located on?

What enzyme does H code for?

A

19

FUT1

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7
Q

What does FUT1 do?

A

Fucosyl transferase
adds L-fucose to terminal sugar on type 2 chain
a1-2 linkage
Gluc>Gal>GlcNAN>(1-4)Gal >(1-2) Fuc

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8
Q

What chromosome are ABO genes on?

A

Chromosome 9

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9
Q

What does A gene code for?

A

N-acetylgalactosamyl transferase

add GalNAc to Gal of H chain in a1-3 linkage

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10
Q

What does B gene code for?

A

D-galactose transferase

adds D-galactose to Gal of H chain in a1-3 chain

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11
Q

What causes O phenotype?

A

O gene codes for non-functional transferase

O01 and O02 caused by a deletion and framshift leading to truncated protein

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12
Q

AA critical in determining A and B genes?

A

Gly235Ser, Leu266Met, Gly268Ala

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13
Q

What type of chains are ABO antigens carried on?

A

A and B antigens are a terminal sugar attached to oliosaccharide chain carried on glycoproteins 90% and glycosphingolipids 10%

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14
Q

ABH antigens on glycoproteins are on what kind of chain

A

ABH antigens are mainly on N-GLycans containing polyactosaminyl units on Band 3 (DI), the glucose transport protein, RhAG, and CHIP-1 (CO)

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15
Q

What gestational age is ABO antigen detected?

A

5-6 weeks

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16
Q

What age are ABO antigens full formed?

A

By 2-4 years of age

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17
Q

What race has a stronger B antigens

A

Blacks, also have 20% Group B

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18
Q

Most to least H antigen

A

O > A2 > A2B > B > A1 > A1B

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19
Q

What is classic Bombay?

A

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

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20
Q

Allo Anti-H

A

Anti-H in bombay is very potent
Predominatly IgM that reacts at 4-37C
Often stronger at IS then AHG phase

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21
Q

What disease is also produces Oh phenotype?

A

LAD - Leukocyte adhesion deficiency also produces Oh cells due to deficiency in GDP-fucose transporter

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22
Q

What is gene epitasis?

A

where gene masks expresssion of another gene
Epistatic reactions occur because to transferase are required
Ex) H is required for A and B production

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23
Q

What is Para-Bombay?

A

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

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24
Q

What is auto-H?

A 
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
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25
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
26
What blood group is gastric cancer more common?
Group A
27
What blood group is gastric and duodenal ulcers more common in?
Group O
28
Group O and coag factors
Group O has 25% less VIII and vWf? | May tend to bleed more
29
Characteristics of ABO antibodies
IgM, reactive at RT binds complement Group O has anti-A,B - recognizes a shared determinant
30
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
31
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
32
Type 1 chains
Terminal galactose attached in 1-3 linkage present in secretions/ adsorbed onto membrane attached to protein first sugar is GalNAc
33
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
34
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
35
Anti-A lectin - Undiltuted
Dolichos biflorus undiluted | reacts with any group A
36
Anti-B lectin
Griffonia simplicifolia (aged) may also be found as GS II + GalNAc Used to detect acquired B -
37
Anti-A + B lectin
Griffonia simplicifolia (fresh) has weak anti-A activity detects A and B activity
38
Anti-H
Ulex europeaus
39
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
40
A2 subgroup
20% of group A are A2 | A2 is same transferase as A1 but less efficient
41
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)
42
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%
43
A3
mixed field agglutination | Anti-A1 may be present
44
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
45
Aend
MF agglutination but very weak only 10% of cells agglutination No A substance in secretions Anti-A1 usually present
46
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
47
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
48
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)
49
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) ```
50
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
51
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
52
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
53
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
54
Causes of extra reactions in forward type
``` Acquired B Polyagglutination BMT Antibody coated cells Rouleaux ```
55
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
56
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
57
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
58
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
59
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
60
What causes rouleaux?
Abnormal proteins in the plasma seen in MM, cryoglobulinemia, macroglobulinemia
61
Causes of weak reactions in back typing
Decreased antibodies due to age Hypo or agammaglobuliemia Disease (Lymphomas, Waldenstrom's marcroglobuliemia, CLL, Immusuppressive, and Immudeficiency)
62
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)
63
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
64
B3 phenotype
MF reactivity with B substance in secretions
65
Bm
Weak B with B substance in secretions
66
Bx
Weak or negative reaction with anti-B | May have very weak Anit-B present in serum
67
Bel
Weak or negative reaction with Anti-B requires adsorption/elution to detect May have weak anti-B present in serum

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