Blood group antigens and antibodies

Question 1

Where are antigens found?

Answer 1

on all cell surfaces

blood cells have them

Question 2

Where are antibodies found?

Answer 2

in the blood plasma

IgG/IgM

Question 3

How many known blood grouping systems are there?

Answer 3

26

ABO and Rh (D) = most important

Question 4

When can the antigen in the transfused blood stimulate an antibody?

Answer 4

if transfused blood does not have a self antigen

if the person who is getting the transfusion has a different blood group

Question 5

What can stimulate antibody production against blood cells?

Answer 5

blood transfusion ie blood carrying antigens foreign to a patient

pregnancy ie foetal antigen entering the maternal circulation during pregnancy or birth

environmental factors ie naturally acquired
antibodies like anti-A and anti-B

Question 6

What do Antibody-antigen reactions cause in the body?

Answer 6

haemolysis

Question 7

Where can haemolysis occur?

Answer 7

intravascular- directly where red blood cells break up in blood streatm

extravascular- indirectly= liver and spleen remove antibody coated red cells

Question 8

In the lab, what are lab, antibody-antigen reactions used to check for?

Answer 8

agglutination

Question 9

What is agglutination?

Answer 9

red cells clumping together into visible agglutinates by
antigen-antibody reactions

many antibodies crosslink with antigens

Question 10

What does agglutination check in a lab?

Answer 10

If two blood groups are compatible with each other before transfusion

agglutination can be used to type the red cell (see what antigens are present on red cells)

check for the presence of an antibody in the plasma of a
patient (by adding red cells with known antigens to plasma)

Question 11

A and B antigens are very common in the UK. Why can this be a problem?

Answer 11

A and B antigens are very common in the UK (55% of UK people)

this means anti-A, anti-B and anti-AB antibodies are common in UK (97%)

SO= high risk of A or B cells being transfused into someone with the antibody

Question 12

What is the antigen, genotype, antibody and frequency of blood group A?

Answer 12

antigen= A
genotype= AA, AO
antibody= anti B
frequency= 43%

Question 13

What is the antigen, genotype, antibody and frequency of blood group B?

Answer 13

antigen= B
genotype= BB, BO
antibody= anti A
frequency= 9%

Question 14

What is the antigen, genotype, antibody and frequency of blood group O?

Answer 14

antigen= none
genotype= OO
antibody= anti A, anti B
frequency= 45%

Question 15

What is the antigen, genotype, antibody and frequency of blood group AB?

Answer 15

antigen=A, B
genotype= AB
antibody= none
frequency= 3%

Question 16

Even though you havent been exposed to other blood groups why do we have antibodies against them?

Answer 16

gut bacteria wtih A like antigens and B like antigens on them
e.g. if blood group A. immune system recognis A antigen
and make antibody against B antigen

Question 17

What type of antibodies are Anti-A and Anti-B?

Answer 17

IgM

pentameric

Question 18

What are less important blood groups?

Answer 18

main blood group systems= ABO and Rh

less important: kell, duffy, kidd, MNS, P1, Lutheran, and lewis

Question 19

How do you do blood grouping in the lab?

Answer 19

1. take patient blood
2. put in centrifuge
3. separate red cells and plasma (red cells at top and plasma at bottom)
4. red cells tested against anti-A, anti-B and anti-D antibodies
5. if red cell agglutinate, they remain on top of test tube
6. if the dont agglutinate, they move to bottom of test tube

Question 20

How do you test for plasma?

Answer 20

1. mix plasma with group A and group B cells

2. if plasma agglutinates, it shows person has antibodies against cell type being tested

Question 21

Who can O donate to?

Answer 21

O blood group donors can donate to people with any other blood group

Question 22

Who can A donate to?

Answer 22

A blood group or AB blood

group

Question 23

Who can B donate to?

Answer 23

B Ablood group or AB blood

group

Question 24

Who can AB donate to?

Answer 24

AB blood group donors can only donate to people with AB blood group

Question 25

What do you call people with D antigen?

Answer 25

RhD positive (85% of UK)

Question 26

What do you call people without D antigen

Answer 26

RhD negative (15% of UK)

Question 27

How do you test for RhD blood grouping?

Answer 27

the blood is checked to see if it agglutinates with anti-D antibodies, if it does, then the person is RhD positive test is done twice

Question 28

Why is D antigen monitored during transfusion?

Answer 28

D antigen can trigger a very fast and dangerous immune response bc anti-D antibodies are very easily stimulated during pregnancies, anti-D antibodies may be produced, which are IgG and can cross the placenta, this can harm a baby if the baby is RhD+ − this will cause a disease called haemolytic disease of the newborn

Question 29

What is Haemolytic Disease of the Newborn?

Answer 29

1. RhD- plus RhD+ man= baby might be RhD+ 2. if 1ST baby= RhD+= blood from fetus can enter mother's blood during delivery 3. if this happens, mother makes antibodies against RhD 4. this if fine bc it happens after deliver 5. BUT NOW if 2nd baby is RhD+ 6. IgG antibodies pass from mother to placenta into baby 7. damage RBC of fetus= lysis

Question 30

How can you prevent Haemolytic disease of the newborn?

Answer 30

all mothers are screened for blood group and antibodies at antenatal booking (12w) to identify pregnancies at risk of HDN repeat at 28w

Question 31

What can you give a mother who is RhD- and pregnant for the first time with a RhD+ fetus?

Answer 31

- give anti-D antibodies as an injection at 28w (in first preggo) - helps bc anti-D antibodies are able to remove the RhD antigen before the body has an immune reaction to it - now when the mother is pregnant again, there will be no anti-D- atibodies in the mothers circulation and the baby will not be harmed

Question 32

How do you give anti-D injections?

Answer 32

IM

Question 33

When can you give anti-D injections?

Answer 33

any time when fetus and mother blood can mix: - at delivery - abdominal trauma - intrauterine death - spontaneous/tehrapeutic abortion

Question 34

There are antibodies that can cause haemolysis after transfusion. How do we screen for these?

Answer 34

``` 1. mix patient serum with 3 selected screening cells (the antigens on these cells are known) 2. incubate for 15 mins- 37C 3. centrifuge for 5 mins 4. check test tubes: for agglutination 5. cross reference with antigens on 3 cells 6. identify antibody ```

Question 35

What are all red cells covered with?

Answer 35

ZETA POTENTIAL: positively charged ionic cloud- does not allow two red cells to get close to each other

Question 36

Can IgM bring 2 rbc together to agglutinate?

Answer 36

yes | IgM is big enough to bring them close togehter and agglutinate

Question 37

Why can't IgG bring RBC togehter?

Answer 37

too small

Question 38

What antibodies are IgG?

Answer 38

antiD

Question 39

What antibodies are IgM?

Answer 39

antiA, antiB

Question 40

How can you get IgG to agglutinate?

Answer 40

INDIRECT ANTIGLOBULIN TEST - use LISS (LOW IONIC STRENGTH SALINE

Question 41

What does LISS do?

Answer 41

counteracts and breaks down the | zeta potential

Question 42

Whatare the 2 types of cross matching?

Answer 42

immediate spin cross match (ISX) | full direct antiglobulin test cross match

Question 43

What is the immediate spin cross match?

Answer 43

used when the antibody screen is negative it checks donor red cells against patients plasma it is used to check for ABO the donor cells and the patient plasma are mixed, incubated for 2-5 mins and the results are read − a positive result shows agglutination

Question 44

What is full direct antiglobulin test cross match?

Answer 44

used when antibody screen is positive or the patient has a known antibody history for this, antigen negative donor cells are selected, LISS is added, and all this is mixed with patient serum and incubated for 15 mins at 37C