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Haematology Sem 1 > Transfusion lecture 1 > Flashcards

Transfusion lecture 1 Flashcards

1
Q

What are blood group antigens?

A

Antigens carried on protein components (glycoprotiens) present on red cell membranes. Inherited antigens determine blood group specificity

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2
Q

What are blood group antibodies?

A

Proteins produced by an immune response. They are specific to a particular anitgen and can destroy red cells carrying that antigen

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3
Q

What ca blood group antibodies be?

A

IgG (transplant on pregnancy) or IgM (natually occuring)

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4
Q

What is the structure of an antibody?

A

4 polypeptide chains held together by disuphide bonds. 2 heavy chains (50k Da) and 2 light chains (25k Da). These are the same for every antibody. There is a FAB region - fragment antigen binding that is composed of heavy and light chains. Fc region which is fragment crystalliseable. Variable region on each end of the FAB region which is unique to each antibody (specific to antigen).

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5
Q

What are IgG, IgA, IgE, IgD, IgM chains heavy in?

A

y, a, E, delta, u

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6
Q

What is the most important transfusion system?

A

ABO

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7
Q

What do ABO antibodies do?

A

Rapid and total destruction of compatible blood intravascularly. IgM are naturally occuring and cannot pass the placenta.

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8
Q

What are the 4 main blood groups?

A

A, AB, B, O. Distribution varies amongst popularion

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9
Q

What antigens will group A have on their RBC and what antibody will they possess in their plasma?

A

Antigen A on their red blood cells so cannot have anti-A antibodies in plasma (can anti-B antibodies)

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10
Q

What antigens will group B have on their RBC and what antibody will they possess in their plasma?

A

Antigen B on their red blood cells so cannot contain anti-B antibodies on their blood plasma (can have anti-A antibodies)

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11
Q

What antigens will group AB have on their RBC and what antibody will they possess in their plasma?

A

Antigen AB on their RBC and so cannot have anti-B antibodies on their blood plasma

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12
Q

What antigens will group O have on their RBC and what antibody will they possess in their plasma?

A

Antigen H on their RBC and so have anti-A and anti-B antibodies on their blood plasma.

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13
Q

What kind of blood groups would you get if homozygous inheritane?

A

AA, BB, OO

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14
Q

What kind of blood groups would you get if heterozygous inheritance?

A

AO,BO, AB

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15
Q

Which of the blood group is dominant?

A

A and B are codominant

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16
Q

Which of the blood groups are recessive?

A

O is recessive

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17
Q

What can a AO and BO parents have?

A

AB, OO child

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18
Q

Expression of ABO blood groups is controlled on which genetic loci?

A

ABO - 9
H - 19 (FUT1)
Se - 19 (FUT2)

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19
Q

How are genes inherited/?

A

In pairs of mendilia dominants. A&B are codominant and O is AMORPH - no active gene product

20
Q

H antigen is precursor which which antigens?

A

A & B

21
Q

Describe the structure of an antigen?

A

oligosaccharide attatched to glycoprotein inserted into red cell. Expressed on most tissues

22
Q

Can there be variation of A and B antigens on RBC?

A

Yes, some AB types can give a weaker expression due to having less A and B antigens and more H. Still AB blood type though

23
Q

What is the name of the second most important blood group?

A

Rhesus (Rh)

24
Q

How many alleles in Rh blood typing? What are they?

A

6: Cc Dd Ee

25
Q

How is Rh inheritied

A

inherited through 2 structurally similar/related genes on chromosone 1: RhD and RdCE

26
Q

What is the main Rh antigen used in transfusion?

A

D. If youre + then youre RHD+ (85%) and if youre - then RhD- (15%)

27
Q

What causes RhD-

A

weak expression of D antigen

qualitive differences in RhD antigen results in RhD-

28
Q

What are the main complications of RhD?

A

haemolytic disease of the newborn

29
Q

What are Rh antibodies?

A

Not naturally occuring. They are immune antibodies RhG that form through blood transfusion or pregnancy. They react at 37 degrees. The most common antibody is anti-D antibody and it is the most immunogenic (causes immune reponse). Can cross the placenta

30
Q

How is inheritance of Rh calculated?

A

Fishers CDE which has to do with 3 pairs of closelty linked genes. Allows 3 possible halotypes. Still used in the UK

Two-locus model focuses on RhD and RhCE

Both have 8 possible halotypes and 36 geneotypes

31
Q

What are irregular antibodies?

A

Antibodies of other systems. They result from pregnancy and transfusion which are clinically significant when dealing with blood transfusions

32
Q

What is haemolytic disease of the newborn?

A

Alloimmune condition that develops in the foetus causing haemolytic anaemia.

33
Q

What causes haemolytic disease of the newborn?

A

Foetal cells pass into materal circulation through transplacental bleed at delivery or due to post natal trauma.
Mother becomes sensitised by D antigen
Mother produces IgG anti-D antibodies which can cross the placenta
Although the pregnancy that caused the bleed will usually be OK, if the next pregnancy has a RhD+ child, mother’s anti-D antibodies will cause haemolysis of the baby’s red cells

34
Q

Anti-D prophalyxis is a good treatment with bothers who have IgG RhD+ blood type, what has this lead to?

A

An increase in cases of anti-C and anti-K antibodies but all antigens can cause HDNB

35
Q

What is the clinical effect on a RhD+ foetus when its mother has anti-D antibodies?

A

Depends on the type of antibodies.
Hb falls due to haemolysis of RBC.
Raised biliruben due to breakdown of Hb
Causes brain damage to less O2 to brain
Interuterine death from hydrops foetalis (accumulation of fluid in 2 or more faetal compartments
Foetus is pale and swollen with fluid ffrom body cavity and brain - causing brain death

Milder forms result in babies being born with jaundice and anaemia

36
Q

How would you use tests to determine HDNB?

A

Amniocentisis - tests for antibodies and biliruben
Chronic villus sampling (CVS) - check for Rh type
PCR tests mothers blood for foetal DNA
Velocimetry - measures blood flow through foetal cerebral artery
Blood transfusion to foetus in utero

37
Q

What can you give mothers who are anti-D antibody positive?

A

Prophalytics

38
Q

How do prophalytics help?

A

Stop disease occuring before event. If baby is Rh+ then mother needs to be treated within 72 hours or she will develop anti-D antibodies. This is determined by measuring the level of foetal-maternal haemorrhage (FMH) . 500 IU D immunoglobulin administered by 4ml FML

39
Q

How is FMH measured?

A

kleihaur - cheap, simple, not very accurate

flow cytometry - time consuming, expensive but highly accurate

40
Q

What other antibodies cause HDNB

A 
anti C
anti c
anti E
anti e
anti k
anti Fya

4 deaths a year from C and K

41
Q

What is the importance in haemoglobination and blood group testing?

A

Lab testing in transfusion determies recipients ABO and Rh group
antibody screening so irregular antibodies can be detected, NOT ABO antibodies

42
Q

If antibody screen comes out negative?

A

choose units of same blood group if possible
add donors RBC to recipient plasma and incubate at 37 degrees. Check for agglutination and if no clumbin then donor red cells are compatible

Can be tested on haemoglutination smears, in test rubes and blood grouping cassettes

43
Q

If positive antibody screen?

A

indicates presence of irregular antibodied due to previous transfusion or pregnancy. The antibody must be identified and cross match blood to negative antigen. Blood might not be in stock and will need to be ordered and may need to wait

44
Q

How to carry out antibody screening

A

3 cell screens with commercially produced antigens and group o red cells Add patient plasma to screening cells, incubate, obsereve agluttination, record results and interpret results

45
Q

If antibody screening is positive then full antibody idenificatio

A

Variety of antigens and O red cells. Patient plasma to panel red cells. incubate, aluttination observed recorded and inrerpreted.

Haematology Sem 1 (8 decks)

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