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WEEK 11 SEM 4 > Blood group antigens and antibodies > Flashcards

Blood group antigens and antibodies Flashcards

1
Q

Where are antigens found?

A

on all cell surfaces

blood cells have them

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2
Q

Where are antibodies found?

A

in the blood plasma

IgG/IgM

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3
Q

How many known blood grouping systems are there?

A

26

ABO and Rh (D) = most important

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4
Q

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

A

if transfused blood does not have a self antigen

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

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5
Q

What can stimulate antibody production against blood cells?

A

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

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6
Q

What do Antibody-antigen reactions cause in the body?

A

haemolysis

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7
Q

Where can haemolysis occur?

A

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

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

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8
Q

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

A

agglutination

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9
Q

What is agglutination?

A

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

many antibodies crosslink with antigens

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10
Q

What does agglutination check in a lab?

A

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)

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11
Q

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

A

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

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12
Q

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

A 
antigen= A
genotype= AA, AO
antibody= anti B
frequency= 43%
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13
Q

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

A 
antigen= B
genotype= BB, BO
antibody= anti A
frequency= 9%
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14
Q

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

A 
antigen= none
genotype= OO
antibody= anti A, anti B
frequency= 45%
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15
Q

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

A

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

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16
Q

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

A

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

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17
Q

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

A

IgM

pentameric

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18
Q

What are less important blood groups?

A

main blood group systems= ABO and Rh

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

19
Q

How do you do blood grouping in the lab?

A
  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
20
Q

How do you test for plasma?

A
  1. mix plasma with group A and group B cells

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

21
Q

Who can O donate to?

A

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

22
Q

Who can A donate to?

A

A blood group or AB blood

group

23
Q

Who can B donate to?

A

B Ablood group or AB blood

group

24
Q

Who can AB donate to?

A

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

25
Q

What do you call people with D antigen?

A

RhD positive (85% of UK)

26
Q

What do you call people without D antigen

A

RhD negative (15% of UK)

27
Q

How do you test for RhD blood grouping?

A

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

28
Q

Why is D antigen monitored during transfusion?

A

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

29
Q

What is Haemolytic Disease of the Newborn?

A
  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
30
Q

How can you prevent Haemolytic disease of the newborn?

A

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

31
Q

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

A
  • 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
32
Q

How do you give anti-D injections?

A

IM

33
Q

When can you give anti-D injections?

A

any time when fetus and mother blood can mix:

  • at delivery
  • abdominal trauma
  • intrauterine death
  • spontaneous/tehrapeutic abortion
34
Q

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

A 
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
35
Q

What are all red cells covered with?

A

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

36
Q

Can IgM bring 2 rbc together to agglutinate?

A

yes

IgM is big enough to bring them close togehter and agglutinate

37
Q

Why can’t IgG bring RBC togehter?

A

too small

38
Q

What antibodies are IgG?

A

antiD

39
Q

What antibodies are IgM?

A

antiA, antiB

40
Q

How can you get IgG to agglutinate?

A

INDIRECT ANTIGLOBULIN TEST

  • use LISS (LOW IONIC STRENGTH SALINE
41
Q

What does LISS do?

A

counteracts and breaks down the

zeta potential

42
Q

Whatare the 2 types of cross matching?

A

immediate spin cross match (ISX)

full direct antiglobulin test cross match

43
Q

What is the immediate spin cross match?

A

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

44
Q

What is full direct antiglobulin test cross match?

A

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

WEEK 11 SEM 4 (9 decks)

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