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ABO/DNA/ID/Rh Flashcards

1
Q

What is a blood group?

A

An inherited character of the red cell surface detected by a specific antibody

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2
Q

Define blood group system

A

One or more antigens controlled at a single gene locus, or by two or more very closely linked homologous genes with little/ no observable recombination between them

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3
Q

Give the 4 possible functions of blood groups

A
  1. Recognition of self and non self
  2. Maintenance of cellular integrity
  3. Involvement in cell maturation
  4. Susceptibility/ resistance to disease
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4
Q

What are the 2 classes of immunoglobulin which are of interest in terms of blood group antibodies?

A

IgM
IgG

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5
Q

Give the key characteristics of IgM antibodies

A

Pentameteric structure
10 antigen binding sites
A single IgM antibody can bridge the gap and cause agglutination of red cells

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6
Q

Which blood group antibodies are mainly IgM?

A

ABO

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7
Q

Give the key characteristics of IgG antibodies?

A

Monomeric structure
2 antigen binding sites
A single IgG anitbody cannot use in vitro agglutination of red cells

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8
Q

What are the 4 main blood groups in the UK?

A

O, A, B, AB

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9
Q

What are the 3 genes that encode for glycosyltransferase in the prescence of A and B blood groups and where are they enocoded?

A

H gene- Chromosome 19
A gene- Chromosome 9
B gene- Chromosome 9

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10
Q

What are the co-dominant alleles of the ABO system?

A

A and B gene

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11
Q

What carbohydrate to each of the genes add to the chain?

A

H gene- adds fucose residue to the precursor substance
A gene- adds N -acetylgalactosamine residue to H substance
B gene- adds galactose residue to H substance

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12
Q

List the possible genotypes from the 4 blood groups

A

AA, AO, BO, BB, AB, OO

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13
Q

What are the 2 ABO subgroups for the A antigen?

A

A1- approx 80% and dominant to A2
A2- approx 20%

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14
Q

Describe ABO antibodies

A

“Naturally” occuring
Present in the general population, but not present at birth
Develop in the first few months after birth (adult levels by 2-4 years old)

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15
Q

Define Lansteiner’s Law

A

ABO antibodies are found in the plasma against the ABO antigens an individual lacks

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16
Q

Give the key characteristics of the A type RBC’S?

A

Antibodies in plasma- Anti-B
Antigens in RBC- A antigen
Compatible with- A, O

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17
Q

Give the key characteristics of B type RBC’s?

A

Antibodies in plasma- Anti-A
Antigens in RBC- B antigen
Compatible with- B, O

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18
Q

Give the key characteristics of AB type RBC’s?

A

Antibodies in plasma- None
Antigens in RBC- A and B antigens
Compatible with- A, B, AB, O

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19
Q

Give the key characteristics of O RBC’s?

A

Antibodies in plasma- Anti-A and Anti-B
Antigens in RBC- None
Compatible with- O= universal donor

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20
Q

When are ABO antigens fully developed?

A

Over the first 1-2 years of life

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21
Q

When are ABO antibodies fully developed?

A

During the first months of life

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22
Q

Where do ABO antibodies come from?

A

-Maternal milk
- Genetic basis
- Environmental factors
-Evolutionary priming over millions of years to defend against bacteria

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23
Q

True or False: The plasma group of an individual contains Anti-B

A

True

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24
Q

Which genotypes are phenotypically group A?

A

A1A2
A1O
A2O

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25
True or False: B gene encodes for galactose
False It encodes for enzyme that adds the galactose sugar onto residue
26
True or False: Group O blood can be safely given to a group AB individual?
True
27
Summarise the Rh blood group system
Most complex blood group system Comprises 56 antigens Encoded by 2 highly homologous genes on chromosome 1, RHD and RHCE Clinically the most important antigen is D
28
Give the key properties of an Rh polypetide
Protein- associated with glycoprotiens Polymorphic Dependant on active RHAG gene Erythroid specific Antibodies immune
29
What's the role of the RhAG gene?
Found on chromosome 6 and incorporates the antigen into the cell membrane
30
What does it mean to be D positive?
The individual has the RhD gene (most people)
31
Give the RhD frequencies in the UK
85% positive 15% negative
32
Describe the weak D variation of the RhD group
Possesses all normal D antigens, but has quantitatively less RhD positive as a donor and patient Cannot produce anti-D
33
Describe the partial D variation of the RhD group
Lacks part of a normal D antigen Can produce anti-D Can cause the production of anti-D in a D negative recipient RhD +ve as donor and -ve as a patient
34
List the 5 commonly occurring antigens in the Rh system
1. D 2. C 3. c 4. E 5. e
35
How are the Rh antigens inherited?
Inherited as a group of 3 C and c antigens are alleles on the RHCE gene E and e antigens are alleles on the RHCE gene There is no D antigen, if an individual is RhD -ve, they most likely don't have the D antigen
36
What are the 1st order Rh combinations?
CDe- R1 cDE- R2 cde- r
37
What are the 2nd order Rh combinations?
Cde- r' cdE- r'' (RhD negative)
38
What doe sit mean if an individual is Ro?
They have cDe antigens, this is 1st order in black people, but rare in the caucasian population
39
What is Anti-D?
Antibodies that destroy RhD positive red blood cells A major causes of Haemolytic Disease of the Fetus and Newborn (HDFN) Produced in women as a result of sensitisation by red cells from D positive fetus
40
What does Anti-c cause?
HDFN or Haemolytic Transfusion Reaction (HTR)
41
What is HDFN?
Haemolytic Disease of the Fetus and Newborn A condition that affects fetuses and newborns caused by a blood group antibody in the mother attacking red cells in the infant which carries the corresponding antigen (inherited from the father)
42
What is HTR?
Haemolytic Transfusion Reaction
43
Why is Anti-E clinically significant?
It can cause HDFN or HTR Often found together with anti-c in individuals who lack c and E antigens
44
Why is Anti-C clinically significant?
Relatively common, often seen with anti-D Can cause HTR
45
Why is Anti-e clinically significant?
May cause HTR
46
Which type of patients is a full Rh group and match donation important for?
-All female patients under 50yrs old - Patients who need regular transfusions - Patients who have already produced other antibodies
47
True or False: Patients with Partial D can make anti-D
True, they can make it against the part that they are missing
48
True or False: The D antigen is antithetical to the d antigen
False No little d exists
49
True or False: The E antigen is antithetical to the e antigen
True
50
List the main causes of HDFN
- Anti-D - Anti- Kell - Anti-c - Anti-E - Anti- Fya - Other IgG antibodies (-S, -Jka) - ABO antibodies
51
How is fetal anaemia monitored?
Measuring blood flow velocity in MCA More anaemic= higher blood flow to maintain oxygenation
51
How is HDFN diagnosed?
Direct antiglobulin test (DAT) on cord blood Test detects IgG antibody bound to the surface of the infant's red cells
52
How is mild, moderate and severe HDFN?
Mild- phototherapy under UV light Moderate- top-up or exchange transfusion Severe- exchange transfusion at birth Intra-Uterine Transfusion (IUT) during pregnancy
53
What are the requirements for IUT?
5 days old or less, CPD red cells CMV negative Sickle cell -ve -ve for any red cell antibodies Low level of anti-A and anti-B Gamma irradiated
54
Give the 2 mechanisms that cause the immune destruction of red cells
1. Activation of complement 2. Adherance of antibody Fc portions and complement opsonins (C3/C5B) to receptors n cells of the monocyte/ macrophage system
55
Define clinically (in vivo) significant
- Antibody is capable of binding to it's corresponding antigen sand sensitising the red cell- it may activate complement - Antibodies are capable of causing patient morbidity due to the accelerated destruction of transfused cells - Shortens the survival of transfused red cells and/ or causes HDFN
56
Give 3 factors that influence the clinical significance of RBC antibodies
1. Ability of the antibody to activate complement 2. Blood group specificity- no and location of antigen sites 3. No. of antibodies bound per cell
57
What does the indirect anti globulin technique detect?
- 37 degrees active antibodies - IgG antibodies - complement fixing antibodies - all Rh antibodies
58
What does Saline (20 degrees) detect?
- IgM antibodies - Antibodies which may give unclear IAT
59
What is the identification criteria of an antibody that a panel must give?
1. +ve result against 2 cells which contain the antigen 2. -ve result against 2 cells which lack the antigen 3. exclude the presence of any other antibodies
60
Describe RCI molecular RBC typing
Provides a full genetic type for clinically significant antigens (except ABO) Simple 3 step procedure wiht minimal 'hands-on' time, results in less than 3 hours PCR cyclers are present in most labs
61
Give 3 reasons why molecular RBC typing is clinically valued
1. DAT positve patients 2. Multi-transfused patients 3. Patients with weak expression of antigen
62
Outline the process of RBC typing
1. Extract DNA (30 mins) 2. Prepare tests (10-30 mins) 3. Amplify DNA using a thermocycler (approx 2 hours) 4. Analaysis (10 mins)
63
Give 3 advantages of RBC typing
1. Results can be obtained the same day 2. Reproducible, low fail rate 3. Simple to use and not labour intensive
64
Give 3 disadvantages of RBC typing
1. Not suitbale for urgent cases 2. Not as fast as serological typing 3. Not suitable for rare genotypes- requires sequencing
65

AP0509 (4 decks)

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