Carbohydrate Antigens Flashcards
Enzyme that converts i to I
B-1,6-acetylglucosaminyltransferase
Gene
I
IGnT or GCNT2
Number of antigen sites
I
32,000-500,000
Number of antigen sites
i
20,000-70,000
Location in RBC membrane:
I/i
Glycoproteins, glycolipids, Band 3
Present in which body fluids:
I/i
Saliva Milk Amniotic fluid Urine Ovarian cyst
Present on which other blood cells:
I/i
Lymphocytes
Monocytes
Platelets
Granulocytes
Expression on adult cells:
I/i
I: strong
i: weak
Complete conversion around age 2
Expression on cord cells:
I/i
I: weak
i: strong
i adult phenotype without cataracts
Autosomal recessive
Mutation in exon 3 of GCNT2
Auto anti-I
Ig class
IgM
Auto anti-I
Temp of reactivity
RT to 4C- benign
30-37: pathogenic
Auto anti-I
Bind complement
Rarely
Auto anti-I
Hemolysis in vitro
No
Auto anti-I
Reactivity with enzyme treated RBCs
Increased
Auto anti-I
HTR/HDFN
No
Alloanti-I
Ig class
IgM
Alloanti-I
Bind complement
Rarely
Alloanti-I
Hemolysis in vitro
No
Alloanti-I
Temp of reactivity
RT - 4 C
Rarely 37
Alloanti-I
Reactivity with enzyme treated RBCs
Increased
Alloanti-I
HDFN
No
Alloanti-I
HTR
None to rare
Auto anti-i
Ig class
IgM
Auto anti-i
Temp of reactivity
RT-4C: benign
30-37: pathologic
Auto anti-i
Bind complement
Rarely
Auto anti-i
Hemolysis in vitro
No
Auto anti-i
Reactivity with enzyme treated RBCs
Increased
Auto anti-i
HTR/HDFN
No
Chain type of ABH In secretions
Also adsorbed onto RBCs
Type 1 chain
Chain type of most ABH on RBCs
Type 2 chain
H gene (FUT1) encodes
a-2-L-fucosyltransferase
H antigen expression
O>A2>B>A2B>A1>A1B>Bombay
ABO antibodies
Detection age
3-6 months
ABO antibodies
Adult levels reached
5-10 years
ABO antibodies
Titers
Vary from 4- >2048
Anti-A titers higher than anti-B
Titers higher in group O individuals than A or B
ABO antibodies
Ig class
Mostly IgM
Group Os have a mix of IgG and IgM
ABO antibodies
Temp of reactivity
4C
IgG will also react at 37
ABO antibodies
In vitro hemolysis
Yes (intravascular)
ABO antibodies
HTR
Yes
ABO antibodies
HDFN
Yes, usually mild
Lectin
Bandeiraea simplicifolia
Anti-B
Lectin
Dolichos biflorus
Anti-A1
Lectin
Ulex europaeus
Anti-H
Lectin
Phaseolus limensis
Anti-A
Lectin
Helix pomatia
Anti-A
Snails
Lectin
Anguilla japonica
Anti-H
Eel
Terminal epitope
A antigen
N-acetylgalactosamine
Terminal epitope
B antigen
Galactose
Terminal epitope
H antigen
Fucose
ABO antigen age of detection
5-6 week gestation
Adult levels 2-4 years (precursor chains branch with age allowing for more antigen expression)
ABO gene location
Chromosome 9q34
A1
80% of A donors
Approx 5x the A than A2
A2
Most common subtype @ 20%
Inefficient conversion of H
Less A antigen more H
Acquired B
Deacetylation of the A antigen yields a B like galactosamine
Typically shows weak agglutination with anti-B reagents w/ negative auto control
Acquired B disease associations
Infection by gastrointestinal bacteria
Acquired B resolution
Type patient cells with different monoclonal reagent or acidified (pH 6) anti-B
Anti-A1 frequency in A2 individuals
1-8% A2
22-35% A2B
Anti-A1
Ig class
Usually IgM
Anti-A1
Temp of reactivity
Usually RT or below- clinically insignificant
Rarely 37- clinically significant
Lewis antigen present on which cells/tissues
Platelets
Endothelial cells
Kidney tissue
Genitourinary and gastrointestinal epithelium
Lewis antigen on RBCs
NOT synthesized by RBCs
Passively adsorbed onto the cell membrane
May be eluted with increase plasma volume or increased circulating lipoprotein
Levels decrease on stored RBCs
Lewis and secretor gene
Leb +
Lewis gene but no secretor gene
Lea+
Le(a+b+)
Transiently seen in infants while secretor activity increases
Seen in Asian populations where weak secretor gene is common (18% Japanese)
Lewis expression in newborns
Le(a-b-)
Valid phenotype not present til age 5-6
Lewis phenotype prevalence:
European
Le(a+b-): 22%
Le(a-b+): 72%
Le(a-b-): 6%
Le(a+b+): rare
Lewis phenotype prevalence:
African
Le(a+b-): 23%
Le(a-b+): 55%
Le(a-b-): 22%
Le(a+b+): rare
Lewis antibodies
Ig class
Generally IgM
Lewis antibodies
In Le(a-b+) individuals
Do not make anti-Lea as trace amount of Lea is synthesized
Anti-Leb
May show abo specificity
Most common anti-Leb H
Lewis antibodies
HDN
Unlikely
Antigens readily shed from cells after transfusion
Antigen negative RBCs generally not indicated for most patients
Lewis antibodies
HDFN
No
Predominantly IgM and antigen poorly expressed on neonate RBCs
GCNT2 (I) chromosome location
6p24
Difference between i adult w/cataracts and w/o cataracts
W/o cataracts mutation is in Exon 1c which is specific for I synthesis in RBCs (so none on red cells but present on other tissue)
W/ cataracts is gene deletion or mutation in exon 2 or 3 meaning I synthesis is lost in all tissues
Anti-i disease association
Infectious mononucleosis
P1 and P2 phenotypes both express
Pk and P
Rare recessive phenotypes in P1PK/GLOB
P1k, P2k, p
Associated with natural production of antibodies
P, Pk, P1 synthesis
Stepwise addition of sugars to lactosylceramide
Pk synthesized first- precursor of all globo-series glycosphingolipids
Pk requires what gene
A4GALT
Pk is a substrate for what enzyme
B1-3-N-acetylgalactosaminyltransferase
(B3GALNT1)
forms P antigen
P1
A4GALT adds galactose to paragloboside
p phenotype
Mutation in A4GALT
Loss of all globo family and P1
ABO discrepancies
Missing/Weak antigen
subgroup of A/B
suppressed antigen
ABO discrepancies
extra/unexpected antigen
acquired B
B(A)
antibody coating cells
ABO discrepancies
missing/weak antibody
age
Hypo or agammaglobuliemia
Disease (Lymphomas, Waldenstrom’s marcroglobuliemia, CLL, Immusuppressive, and Immudeficiency)
ABO discrepancy
extra/unexpected antibody
rouleaux anti-A1 autoantibody cold alloantibody passively acquired antibody
A3
weakly positive with anti-A
mf
Aend
MF agglutination but very weak
only 10% of cells agglutination
No A substance in secretions
Anti-A1 usually 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
Am
negative with anti-A
adsorbs/elutes anti-A or -A,B
secretes A & H
Ay
negative with anti-A
adsorbs/elutes anti-A or -A,B
secretes weak A and H
Ael
negative with anti-A
adsorbs/elutes anti-A or -A,B
secretes only H
B(A)
super B gene produces a–3-N-acetylgalactosaminyltransferase
extra “A like” antigen
Lewis gene/chromosome
FUT3
chromosome 19
P phenotypes frequency
Caucasion
P1: 79% P2: 21% p: rare P1k: very rare P2k: very rare
P phenotypes frequency
African American
P1: 94% P2: 6% p: rare P1k: very rare P2k: very rare
p (null phenotype)
lack P1, P, and Pk
High prevalence in P1PK/GLOB
Pk, P, PX2, LKE
P Asian frequencies:
P1: 20% P2: 80% p: rare P1k: rare P2k: rare
B3GALNT1 mutation
Pk phenotype
Loss of P, LKE, and PX2
Anti-P1
Naturally occurring IgM present in 25-33% of P2 individuals
Anti-P1
HDFN/HTR
Rarely crossed placenta- no HDFN
Rare reactivity at 37 or invitro hemolysis
P1 levels during storage
Decrease
P1 expression
Varies in strength among individuals
Anti-P1 may not react with all P1 + cells
Anti-P1 with enzyme treated cells
Reactivity enhanced
Anti-P1 inhibited by:
Hydatid cyst fluid
P1 substance from pigeon eggs
Anti-PP1Pk (anti-Tja)
Separable mixture of the antibodies found in p people
Alloanti-P (in P1k, P2k, and p) characteristics
Naturally occurring
Predominantly IgM or a mix of IgM and IgG
Associated with hemolytic transfusion reaction and occasional HDFN
ASSOCIATED WITH RECURRENT SPONTANEOUS ABORTIONS (placenta rich in P and Pk antigen)
Auto anti-P association
Paroxysmal cold hemoglobinuria
Donath landsteiner test
FORS1 characteristics
Addition of N-acetylgalactosamine to the P antigen
Resembles the A antigen and may be picked up by certain anti-A reagents (originally thought to be an A subgroup)
Gene: GBGT1
Most people have naturally occurring anti-FORS1
How is Pk antigen formed?
A4GALT enzyme adds galactose to Lactosylceramide
How is P antigen formed?
P antigen is formed from Pk
B3GALNT-1 adds GalNAc to Pk > P antigen
How is NOR antigen formed?
Formed from P antigen
A4GALT enzyme adds galactose to P antigen
How is LKE antigen formed?
Formed from P antigen
A4GALT enzyme adds galactose and sialic acid is added to form LKE
Characteristics of P1 antigen
Weaker on cord cells until 10 years of age
Antigen varies in strength and is weaker on older cells
Enzymes enhance reactivity
Not destroyed by Papain, Ficin, EGA, DTT, Chloroquine
What disease is Pk antigen associated with?
Receptor for shiga toxin
Receptor for Streptoccocus suis
What disease is P antigen associated with
Receptor for parvovirus
Disease associated with anti-I
Mycoplasma pnuemoniae
Characteristics of pathological auto anti-I in CHD
Reacts at 32C and activates complement at 30-37C
Titer is > 500 at 4C and >128 at room temp
Will hemolyze enzyme treated cells at low pH
Antibody is typically monoclonal or idiopathic
Characteristics of benign auto-I?
Reacts at <25C and activates Complement at <25C
Titer is < 64 at 4C and <16 at room temp
Antibody is polyclonal
Diseases and Ii concentration
Increased I and i is found in chronic hemolytic disorders and is a sign of stresses erythropoiesis
- Thalassemia major
- Hypoplastic anemia
- CLL
- Acute leukemia
- Bombay phenotype
What chromosome is Le gene located on?
Chromosome 19
Leb is a receptor for…
H. pylori - bacteria responsible for causing gastritis
Norovirus
What is Le(a-b-) associated with?
Increased susceptibility to E. Coli, candida, Cardiovascular disease, and possibly graft failure in renal transplant patients
What chromosome is H gene located on
Chromosome 19
What disease is also produces Oh phenotype
LAD - Leukocyte adhesion deficiency also produces Oh cells due to deficiency in GDP-fucose transporter
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
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
ABO frequency
European
O: 45%
A: 40%
B: 11%
AB: 4%
ABO frequency
African American
O: 49%
A: 27%
B: 20%
AB: 4%
H disease associations
Helicobacter pylori
Norovirus
Anti-Le^ab
Inseparable anti-lea and -Leb
