Rh & other blood groups

Question 1

explain the concept of dosage (2 ways)

Answer 1

• A person who is homozygous for an Ag expresses more of that Ag than a person who is heterozygous
• Ab reacts strongly to homozygous Ag bc more of that specific Ag.

Question 2

Antigens of which blood groups in this lecture are destroyed by enzyme treatment? Enhanced by enzyme
treatment?

Answer 2

• Destroyed: M/N, S/s, Fya, Fyb

- Enhanced: C,c, D, E, e, Jka, Jkb

Question 3

Why are Kidd antibodies so difficult to work with?

Answer 3

• often weak: require Ag to be enzyme-treated
• Demonstrate dosage: Homozygous Ag works better
• Found in combo. w/ other Ab

Question 4

Why is there a racial difference in Duffy phenotype

distribution?

Answer 4

• among Africans bc Africa highly susceptible to P. vivax (disease carried by mosquitoes)
  => adjust to selective pressure

Question 5

Explain the inheritance of Rh antigens.

Answer 5

Rh genes inherited as haplotype e.g. DCe (one set of gene)

e.g. If child has genotype DCe/dce, may have gotten DCe from mum & dce from dad

Question 6

Why is the D antigen so immunogenic?

Answer 6

bc it contains ≥30 diff. epitopes: 9 epitopes exposed on extracell. surface.

Question 7

Explain the difference between the Fisher-Race and Weiner nomenclature. What would be the W nomenclature if it’s F-R is DCe/dce

Answer 7

a) * both refers to Ag C, c, D, E, e but written diff.
- F-R: written as haplotype
- Weiner: written w/ R/r and numbers/primers (‘)
b) R1r

Question 8

Explain the nomenclature of Wiener (for Rh nomenclature)

Answer 8

• R = D Ag expressed
• r = D Ag NOT expressed
• R1 or r’ = C & e (DCe or dCe)
• R2 or r’’ = c & E (DcE or dcE)
• R0 or r = c & e (Dce or dce)

Question 9

What is the class of each of the antibodies in the MNS
blood group?

Answer 9

• Anti-M & -N: IgM or IgG

- Anti-S & -s: IgG

Question 10

Characteristics of Ag in Rh blood group

Answer 10

• C, e, D, E, e (d = Absence of D Ag)
• well developed @ birth
• enhanced by enzyme treatment

Question 11

Characteristics of Ab in Rh blood group

Answer 11

• IgG*
• IR => opsinisation = phagocytose = extravascular haemolysis
• react optimally @ 37ºC
• detected by IAT
• Anti-C, -c, -E, -e demonstrate dosage (strong rxn)
• Hi clinically sig. for HTR, HDNB

Question 12

Characteristics of Ag in Kell blood group

Answer 12

• K, k
• protein
• antithetical pair expressed in co-dominant
• well developed @ birth
• K highly immunogenic
• Not destroyed by enzymes but destroyed by reducing agents

Question 13

Characteristics of Ab in Kell blood group

Answer 13

• IgG
• best detected @ 37ºC w/ IAT
• Anti-K can cause HTR & HDNB
• Finding compatible blood for a person that also expresses anti-k is hard bc rare

Question 14

Difference b/w Weak D & partial D

Answer 14

• Weak: Dec. expression of D Ag = considered Rh(D) pos
• Partial: region of RHD replaced by regions of RHCE => part of D Ag is missing
  = Donors - have partial D = Rh(D) pos
  = Recipient - have partial D = Rh(D) neg so that they are given Rh(D) neg cells (as they’ll have a-D Ab = must not react)

Question 15

Difference in testing when Rh(D) is complete vs weak/partial (type of Ig)

Answer 15

Complete: ABO FWD gp w/ IgM anti-D

Weak/partial: Weak D test using IAT w/ IgG anti-D (done donor/newborns)