intro to transfusion science

Question 1

What is a blood group?

Answer 1

1/+ RBC surface Ag controlled by an allelic gene

Question 2

International society of blood transfusion (ISBT) blood group requirements

Answer 2

• Ag must be inherited (by mum & dad)
• gene identified & sequenced w/ its chromosomal location known
• gene must be unique/different from all other genes - encode for the Ag of existing blood groups
• corresponding alloantibody must be identified

Question 3

Characteristics of RBC Ag

Answer 3

• complex protein / carbohydrate structures on RBC membrane

- RBC Ag caused by SNP (mutation in gene) causing change in a) Ag protein or b) glycosylaminotransferase enzyme

Question 4

difference b/w Ag & Ab in transfusion science

Answer 4

Ag: substance that can stimulate an IR that is detected as foreign
Ab: proteins made by I.Sys. in response to specific Ag

Question 5

Describe the features of the 2 main Ab/Ig encountered in transfusion science

Answer 5

• IgM: polymer?, 30nm => direct agglutination, can’t cross placenta
• IgG: monomer?, 12nm => indirect agglutination, can cross placenta

Question 6

2 main types of RBC Ag

Answer 6

• ABO

- Rhesus (Rh)

Question 7

explain the kinetics of the IR (ie. 1º & 2º exposure to Ag)

Answer 7

1º: Long lag (5-7 days), IgM > IgG, develop memory cell

2º: Short lag (2-3 days), IgM < IgG, high avidity

Question 8

Define & explain characteristics of the 2 RBC Ab: naturally occurring & immune Ab

Answer 8

• Naturally occurring: present in plasma w/out immunisation but not present @ birth: Ab made twds Ag of gut bacteria while developing. IgM = complete = direct
• Immune Ab: Ab produced after exposure to Ag. IgG = incomplete = indirect

Question 9

What can in vivo RBC Ag-Ab binding result to in the context of transfusion science?

Answer 9

=> intra / extravascular haemolysis = BAD

• e.g. haemolytic transfusion reaction (HTR)
• e.g. haemolytic disease of newborn (HDNB)

Question 10

Describe the haemagglutination of IgM & IgG Ab

Answer 10

• RBC are separated 20nm from each other due to Seta potential (-18MV)
• IgM: direct agglut. bc big enough (30nm) - can crosslink w/ adjacent RBC w/out being affected by the repulsion forces of ZETA
• IgG: indirect bc can’t be used for agglutination alone (12nm)

Question 11

Describe the appearance of agglutination in grading the tube reactions

Answer 11

0: no agglutinates, leave bottom easily
1+: small agglutinates w/ red background
2+: many medium sized agglutinates
3+: one/tow large agglutinates w/ some little ones
4+ One large cell agglutinate

Question 12

in vitro RBC Ag/Ab binding can be used to: (4)

Answer 12

• determine blood group
• crossmatch: compatibility of donor & recipient
• Identify Ab in plasma
• determine if indiv.’s RBC coated w/ Ab