Transfusion lecture 1

Question 1

What are blood group antigens?

Answer 1

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

Question 2

What are blood group antibodies?

Answer 2

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

Question 3

What ca blood group antibodies be?

Answer 3

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

Question 4

What is the structure of an antibody?

Answer 4

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).

Question 5

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

Answer 5

y, a, E, delta, u

Question 6

What is the most important transfusion system?

Answer 6

ABO

Question 7

What do ABO antibodies do?

Answer 7

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

Question 8

What are the 4 main blood groups?

Answer 8

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

Question 9

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

Answer 9

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

Question 10

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

Answer 10

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

Question 11

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

Answer 11

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

Question 12

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

Answer 12

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

Question 13

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

Answer 13

AA, BB, OO

Question 14

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

Answer 14

AO,BO, AB

Question 15

Which of the blood group is dominant?

Answer 15

A and B are codominant

Question 16

Which of the blood groups are recessive?

Answer 16

O is recessive

Question 17

What can a AO and BO parents have?

Answer 17

AB, OO child

Question 18

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

Answer 18

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

Question 19

How are genes inherited/?

Answer 19

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

Question 20

H antigen is precursor which which antigens?

Answer 20

A & B

Question 21

Describe the structure of an antigen?

Answer 21

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

Question 22

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

Answer 22

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

Question 23

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

Answer 23

Rhesus (Rh)

Question 24

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

Answer 24

6: Cc Dd Ee

Question 25

How is Rh inheritied

Answer 25

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

Question 26

What is the main Rh antigen used in transfusion?

Answer 26

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

Question 27

What causes RhD-

Answer 27

weak expression of D antigen | qualitive differences in RhD antigen results in RhD-

Question 28

What are the main complications of RhD?

Answer 28

haemolytic disease of the newborn

Question 29

What are Rh antibodies?

Answer 29

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

Question 30

How is inheritance of Rh calculated?

Answer 30

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

Question 31

What are irregular antibodies?

Answer 31

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

Question 32

What is haemolytic disease of the newborn?

Answer 32

Alloimmune condition that develops in the foetus causing haemolytic anaemia.

Question 33

What causes haemolytic disease of the newborn?

Answer 33

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

Question 34

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

Answer 34

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

Question 35

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

Answer 35

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

Question 36

How would you use tests to determine HDNB?

Answer 36

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

Question 37

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

Answer 37

Prophalytics

Question 38

How do prophalytics help?

Answer 38

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

Question 39

How is FMH measured?

Answer 39

kleihaur - cheap, simple, not very accurate | flow cytometry - time consuming, expensive but highly accurate

Question 40

What other antibodies cause HDNB

Answer 40

``` anti C anti c anti E anti e anti k anti Fya ``` 4 deaths a year from C and K

Question 41

What is the importance in haemoglobination and blood group testing?

Answer 41

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

Question 42

If antibody screen comes out negative?

Answer 42

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

Question 43

If positive antibody screen?

Answer 43

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

Question 44

How to carry out antibody screening

Answer 44

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

Question 45

If antibody screening is positive then full antibody idenificatio

Answer 45

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