Blood Groups

Question 1

how many blood group systems are there?

Answer 1

26

Question 2

what are the most important blood group systems?

Answer 2

ABO and Rhesus

Question 3

when do IgG antibodies mainly occur?

Answer 3

• exposure to blood transfusions

- foeto-maternal transmission

Question 4

why might IgM antibodies occur?

Answer 4

due to components in food which mimic A and B antigens

Question 5

what is H substance?

Answer 5

• a precursor to each of the ABO blood group antigens

- found on chromosome 19

Question 6

which genes code for substance H?

Answer 6

FUT1 and FUT2

Question 7

what do FUT1 and FUT2 genes code for?

Answer 7

H substance

Question 8

what do A and B genes code for?

Answer 8

glucosyl transferases - add further sugar groups

Question 9

on what chromosome are A and B genes found?

Answer 9

9

Question 10

what naturally occurring antibodies are found in antigen O?

Answer 10

anti-A, anti-B

Question 11

what naturally occurring antibodies are found in antigen A?

Answer 11

anti-B

Question 12

what naturally occurring antibodies are found in antigen B?

Answer 12

anti-A

Question 13

what naturally occurring antibodies are found in antigen AB?

Answer 13

none

Question 14

what antigens are there in the Rhesus system?

Answer 14

• c
• C
• D
• e
• E

Question 15

what does rhesus negative imply?

Answer 15

D negative

Question 16

how are rhesus antibodies acquired?

Answer 16

• not naturally occurring
• IgG antibodies, acquired through exposure to Rh-positive blood
• develop in response to pregnancy or transfusion

Question 17

how does haemolytic disease of newborns occur?

Answer 17

1. foetal red cells carrying antigens from father transfer into maternal circulation
2. mother produces IgG antibodies to e.g D, c, E, Kell
3. antibodies cross placenta causing:
   - anaemia
   - jaundice
   - brain damage
   - foetal death

Question 18

how is rhesus D prevented/immunised against?

Answer 18

• anti-D prophylaxis given to D negative mothers at 28 weeks and delivery (40 weeks)
• kleihauer test looks for foetal cells in maternal circulation
• foetal monitoring by ultrasound
• can receive intra-uterine transfusion

Question 19

what are acute haemolytic reactions and how do they occur?

Answer 19

• pre-existing antibodies
• usually due to mis-matched blood
• ABO most serious

Question 20

what are different types of transfusion reactions that can occur?

Answer 20

• acute haemolytic reactions
• delayed haemolytic reactions
• urticaria or anaphylaxis (drugs or plasma proteins)
• febrile reactions (HLA antibodies)