RH Blood Group System

Question 1

Who discovered the RH system and when?

Answer 1

Landsteiner and Wiener, 1940.

Question 2

How was the RH system discovered?

Answer 2

Antibodies were raised by injecting RBCs of rhesus monkeys into rabbits and guinea pigs.

Question 3

What is the RH blood group system?

Answer 3

Rhesus Blood group system.

Question 4

How many Rh antigens are recognized by the ISBT?

Answer 4

49 Rh antigens

Question 5

What are the major Rh antigens?

Answer 5

D, C, c, E, e

Question 6

What are the variants of the Rh antigens?

Answer 6

Cw and G

Question 7

How are Rh antigens inherited?

Answer 7

• Inherited dominantly and the inherited antigens will be expressed in the phenotype.
• Two alleles inherited from each parent: RHD (D-antigen) and RHCE (C, c, E, and e antigen) found on chromosome 1.

Question 8

List the 3 major theories of Rh factor inheritance.

Answer 8

• Fisher-Race theory
• Wiener theory
• Molecular studies

Question 9

What is the Fisher-Race theory?

Answer 9

• Theory of pairs of linked genes
• Supposes that there are 3 pairs of alleles involved in the Rh system
• Opposite to one another (C and c, E and e, D and d), but “d” antigen does not exist
• Genes coding for alleles are closely linked
• Utilizes the CDE nomenclature

Question 10

What is the Wiener theory?

Answer 10

• Theory of multiple allelomorphic genes
• Supposes that there are multiple allelic genes on a single chromosomal locus
• The genes are inherited as a complex, one from the father and the other one from the mother
• Utilizes the Rh-Hr nomenclature

Question 11

What is the molecular study theory?

Answer 11

• There are 2 Rh genes found on the Rh-locus on chromosome 1: RHD and RHCE genes
• RHD gene produces D-antigen
• RHCE gene produces 4 different antigenic combinations: CE, Ce, cE, or ce
• D+ individuals inherited 2 genes, RHD and one allele from the RHCE gene from each parent
• D- individuals inherited 1 gene, the RHCE gene with one allele from each parent, but lack the RHD gene

Question 12

What is Rh positive?

Answer 12

Individuals who have inherited the RHD gene and express D-antigen on their RBC surfaces.

Question 13

What is Rh negative?

Answer 13

Individuals who lacks the RHD gene and does not express D-antigen on their RBC surfaces.

Question 14

What is Cw antigen?

Answer 14

High frequency Rh antigen, rather than an allele of the C antigen.

Question 15

What is G antigen?

Answer 15

Found on cells that are also C+ and D+, because RHC and RHD proteins share the same amino acid sequence that is recognized by anti-G.

Question 16

What is weak D?

Answer 16

Individuals who inherit a gene that is not effective in forming D-antigen due to abnormal expression of RHD gene.

Question 17

What blood should weak D patients be transfused with?

Answer 17

Females: Rh-negative blood
Males: Rh-positive blood

Question 18

What is partial D?

Answer 18

Individuals who have an absence of certain D-antigen epitopes and will produce antibodies against the missing epitopes.

Question 19

What is Rh-null?

Answer 19

• Lacking all the Rh antigens due to homozygosity of a silent allele on the RH-locus or a suppressor gene which is inherited independently of the RH-locus.
• Associated with congenital spherocytosis haemolytic anaemia.

Question 20

What are Rh antibodies?

Answer 20

• Anti-D, C, c, E, e
• Mainly IgG’s and react at 37 degrees
• Does not cause ‘c but extravascular removal of incompatible RBCs
• Immune response: Exposure in pregnancy, transfusions, and immunization.

Question 21

What is the role of RH in HTR?

Answer 21

• IgG antibodies cause extravascular haemolysis.

- There are many antigens on the red cell membrane thus sensitization is effective and causes a severe of HTR.

Question 22

What is the role of RH in HDFN?

Answer 22

Antigen is composed of antigen which causes production of IgG antibodies that can cross the placenta and cause the most severe and common form of HDFN.