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Transfusion 231 > Week 2 > Flashcards

Week 2 Flashcards

1
Q

What occurs in HDFN

A

When mom is negative and baby is positive, the first pregnancy has mom produce Anti-D from the being exposed to D positive cells
-Maternal anti D are able to cross placenta
-the fetal cells in the next pregnancies are destroyed by AntiD if the baby is Rh pos

-mom is protected with Rh neg against the anti D after delivery

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2
Q

What is the difference between the fisher race theory and Wiener Theory

what is the current theory

A

Fisher-Race Theory:
A gene complex is inherited that codes for 3 closely linked set of alleles

Wiener Theory:
1 gene is responsible for the expression of all
Rh Blood Group systems

current :Rh Blood Group
System antigens are determined By 2 genes. Allele D or RHCE

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3
Q

What are Rh Genetics

A

-genes codominant alleles
-RHD= D Ag as heterozygous or homozygous Dd or DD

RHCE genes have 4 alleles at am locus
1) RHCE
2) RHCe
3) RHcE
4) RHce

5 Ag can be found in most ppl

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3
Q

Which AG is most immunogenic

A

D Ag after A and B antigen
-Anti D is seen only if the pt with D Ag is exposed to D pos cells
-Exposure from pregnancy or transfusions

Rh pos/neg is whether there is D AG on RBC

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3
Q

Rh Antibodies- how are they different from ABO system

A

1) Red cell immune: DO NOT produce the antibodies unless exposed to red blood cells through transfusion or pregnancy
2) IgG
3) Poor Complement Binding

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3
Q

What is the structure of Rh Ag

A
  • protein structure-amino acids
    -Elicits an IgG immunogenic response
    -Exposure through transfusion or pregnancy-Red Cell Immune

 Not expressed on tissues
 Well-developed at birth
 Direct gene product (not enzyme)
 RHD/RHCE Genes codes directly for antigen
 Can easily cause Hemolytic Disease of the Fetus and Newborn (HDFN)

-protein that is made up of over 400 AA and crosses RBC membrane 12 times
-Exposed loops are the AG
-Product of RHD gene and RHCE gene

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3
Q

Rh Phenotype vs. Genotype

A

D+C+E-c+e+
Antigens Present, Serologically Detectable

DCe/Dce, Dce/dCe, DCe/dce
Genotype- Possible Genes Inherited

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3
Q

most common antibody in RH neg pt vs Rh pos

A

Anti D in Rh neg

Anti E in Rh pos

Anti e is autoAB hard to find since 98% of pop has e AG

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3
Q

Fisher-Race Nomenclature

A
  • 3 separate genes and their alleles D,C,E, c and e
    -linked on the same chromosome and inherited as a gene complex

AG that are possible are D,C,E, c and e
-d is amorphic or deleted gene
-If D antigen is present, the genotype can be either DD or Dd

DCE, DCe, DcE, Dce, dCE, dCe, dcE, dce

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4
Q

Wiener Nomenclature

A

One gene responsible for the expression of 8 alleles which causes many Rh Ag to be present
-terminology is still used even if the theory was incorrect

Ro, R1, R2, Rz, r, r’, r”, ry

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5
Q

Types of Rh Reagents
Monoclonal Anti-D

A

Monoclonal Anti-D and Polyclonal Anti-D blend – Must be mixed together for Weak D detection

Monoclonal Anti-D – Low protein diluent (6% bovine albumin) containing IgM

at michener we use Anti-D1 and Anti D2

Polyclonal Anti-D Blend – IgG and IgM

-Low protein diluent doesnt promote false positive agglu that you find with high protein D typing reagents

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6
Q

Types of Rh Reagents
Rh Control

A

-protein media can cause false pos
-Rh Control – Low protein diluent (6% bovine albumin) but NO anti-D
Purpose – Detects false positive results. To show reaction is due to anti-D NOT diluent
Should be NEGATIVE to report ABO and Rh typing

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7
Q

When would you have a positive Rh control

A

Positive DAT - AB on the cells (used modified anti D like monoclonal, saline AntiD)

Rouleaux/cold agglutinins - use 3x washed RBCS

Bacterial contamination - repeat

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8
Q

What are three types of weak D

Genetic Weak D

A

Genetic Weak D

D occurs when there are low AG

 Gene codes for less D antigens
 Usually needs IAT Weak D testing
 Does not usually produce Anti-D

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9
Q

What are three types of weak D

C Trans (positional)

A

 Position effect: C antigen inherited in
trans position to D antigen
 Weaker expression of D antigen
 Monoclonal Anti-D can detect
 Does not usually produce Anti-D

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9
Q

What are three types of weak D

Partial D or Mosaic D

A

Missing part of the Rh antigen
 Mutated gene: change in aa, therefore change in protein
 Several variations
 Detected by monoclonal Anti-D or may need Weak D testing (IAT)
 different results with different antisera (polyclonal vs monoclonal)
 Individuals can make Anti-D to the part of the antigen missing

if they are either they need to be treated as Rh neg because you dont want them to produce AB /Anti D

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10
Q

How to detect Weak D?

A

Antisera
-Immediate spin method may have a Weak Positive results- still call Rh Positive
-Immediate spin method may have a Discrepancy in testing
-If automation is used- discrepancy in D1/D2 testing

11
Q

Weak D Policies

A

initial Rh typing on everyone
 If the IS Anti-D is negative :
1) Stop if adult patient, result as Rh Negative

2) Perform Weak D testing on ALL Donors (at CBS) if its D1 and D2 neg then you have to know its actually neg

3) Perform Weak D testing on Rh Negative babies of Rh Negative Moms
IF Weak D testing is POSITIVE, then donors and babies are called Rh Positive.

12
Q

Weak D IAT test

A

To detect these weaker expressions of
the D antigen, we use the IAT method
- do normal D1,d2 if there is less AG then you can have sensitization without agglutination
-incubate Anti D and wash to remove extra antisera, and add ahg
-the AHG will show agglutination if there is sensitization

NO checking under the Microscope
Add CCC to all negative reactions
minimum reaction should be 1+

13
Q

Weak D IAT False positive

A

Weak D testing can be false positive due to in vivo coating of Red cells with IgG antibody
-Rh control is positive
-AHG reacts with the IgG on the RBC membrane even if there is not Anti D attached
-invalid weak D testing

Auto Antibody, Mom’s Antibody on Fetal
cells, and Patient Antibody on donor cells.

14
Q

Molecular Testing for Weak D
policy for testing

A
  • prenatal pts with weak serological RHD results were RHD genotyping can modify their blood product or RhIG needs
    -pt that need chronic transfusions or have complex needs where genotyping can change blood requirements
    -pt who appear serologically D positive but need to be transfused with AntD

-mosiac D is most important because the pt can produce Anti D

15
Q

how to select Rh for transfusion

A
  • Rh AB are red cell immune
    -Rh neg ppl dont automatically make Anti D
    -Rh neg pts can be given Rh pos RBC once safely the AB is produced quickly - antigenic
    -Anti D is an IgG and doesnt bind complement so hemolysis is extravascular (5-10 days)
    -C, E, c, or e antigens not considered unless the pt has corresponding AB
16
Q

What are ABO ABs

A

non red blood cell stimulated
-most clinially significant
-ppl have ABO AB for the AG they lack
-IgM
-activate complement, only one IgM is needed to initiate complement pathway
* Immediate Cell Lysis
* Intravascular Hemolysis
-can cause severe transfusion reactions

17
Q

Landsteiner’s Rules

A

1) A person does not have the antibody to their own antigen.
2) Each person has antibodies to the antigen, they lack (only in the ABO system)

18
Q

ABO Genes
where are they found

A
  • on chromosome 9
    -one allele from each patient
    -A and B are co dominant
    -o gene has no A or B AG, and its expressed until the person is OO
19
Q

What are punnett squares

A

used to determine inheritance possibilities

20
Q

ABO Antigens are found where

A
  • RBC Membranes
  • Endothelial Cells
  • Platelets
  • Lymphocytes
  • Tissue
  • Soluble form found in plasma and other body secretions in a % of populations who have inherited the Secretor gene
  • Several genes and their enzymes are involved in the antigen production.
21
Q

A and B genes code for?

A

enzymes = transferases
-transfer sugar to a basic precursor
substance on the RBC membrane
-ABO antigens are carbohydrates attached through the action of a transferase enzyme

Type 1 Precursor Substance – Beta1-3 linkage (ex. Secretory status)

Type 2 Precursor Substance – Beta1-4 linkage (ex. RBCs)

22
Q

The A & B Antigen Structure

A

-terminal sugars at the end of the long sugar chains (oligosaccharides)
attached to lipids on the RBC
membrane
-last sugars added to the chain
-O doesnt have the A/B ag (has the most
amount of the last terminal sugar called H antigen)
-Ags in different blood groups have the same precursor

23
Q

Antigen Development

A

-A, B, and H antigens are
controlled by the action of transferases.
-*A, B, and H genes each produce a different transferase, adding a specific sugar to the chain.

H Gene – Codes for Fucosyltransferase (FUT 1); Adds L-Fucose to Precursor Substance

A Gene – Codes for N-Acetyl-galactosaminyltransferase; Adds N-Acetylgalactosamine to A Antigen

B Gene – Codes for D-Galactosyltransferase; Adds D-Galactose to A Antigen

NOT all H antigens are converted in A, B, or AB individuals
* IF both A and B genes are present, some H chains are converted to A antigen, while others are converted to B antigen.

24
Q

OO Genotype
what enzyme or Ag is present

A
  • neither enzyme is produced
    -doesnt convert any precursors to A or B AG
    -all have “unconverted” H antigen while A1B have the least H AG
    -O gene is an amorph (does not express a detectable product).
    -Blood Group O is recessive; the trait is expressed when inherited by both parents.

O has most amount of H AG and AB has least

25
Q

Rare and subtypes

A
26
Q

Landsteiner’s Rules for ABO Antibodies

A

In the ABO blood group system,
individuals possess ABO antibodies to the ABO blood group antigens they lack

27
Q

What is the current hypotheses for ABO ab

A

–no known exposure and thought to be naturally occurring or stimulated by other substances
-bacteria or pollen could have structures similar to A/B ag
-environmental exposure would allow ppl to respond immunogenically and produce the AB
-exposure could begin at birth
-Non red cell immune
-newborns cant produce own ABO Ab until they are 3-6 months - maternal AB
-Do not perform RA/RB (Reverse Grouping) if less than 4 months of age.

28
Q

What AB do O group ppl make

A
  • Anti- A, B (IgG)
    -reacts with A or B Ag
    -cant be separated into Anti A or B
29
Q

in routine BB how do we determine ABO GROUP

A

-Reverse cells RA and RB have
the known antigen and are used to test with the patient plasma to determine the unknown antibodies (A1 cells and
B cells).

30
Q

4 Basic categories of Reagents

and basic method of testing

A

1) Red Blood Cells with known antigens
2) Antisera with known antibodies
3) Potentiators to enhance antibody reactions
4) Antihuman Globulin reagents (Polyclonal and Monoclonal)

2 basic methods of testing
immediate spin - IgM
Antiglobulin test - IgG

31
Q

Commercial Antibody Reagents
* Polyclonal antibodies vs monoclonal

A

POLY -made from different clones of B cells with secrete AB with diff specificities
-recognize diff epitopes
-mix of both IgG or IgM

AHG

MONO- made from single clone of transformed B cells that secrete AB of SAME specificity
-one immunoglobulin class IgG or IgM

Uses Hybridoma technology
* Recognizes a single epitope
* E.g., Anti-C, Anti-A, and Anti-IgG

32
Q

ABO Red Cell Testing (ABO Forward Testing)

A

Anti-A, Anti-B, and Anti-A,B are reagents used to determine the ABO blood type, antisera toward specific AG

33
Q

ABO Typing forward vs reverse

A

forward- test pt cell for AG
Reverse - test pt serum for AB

Transfusion 231 (10 decks)

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