RH Blood Group System Flashcards
Who discovered the RH system and when?
Landsteiner and Wiener, 1940.
How was the RH system discovered?
Antibodies were raised by injecting RBCs of rhesus monkeys into rabbits and guinea pigs.
What is the RH blood group system?
Rhesus Blood group system.
How many Rh antigens are recognized by the ISBT?
49 Rh antigens
What are the major Rh antigens?
D, C, c, E, e
What are the variants of the Rh antigens?
Cw and G
How are Rh antigens inherited?
- 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.
List the 3 major theories of Rh factor inheritance.
- Fisher-Race theory
- Wiener theory
- Molecular studies
What is the Fisher-Race theory?
- 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
What is the Wiener theory?
- 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
What is the molecular study theory?
- 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
What is Rh positive?
Individuals who have inherited the RHD gene and express D-antigen on their RBC surfaces.
What is Rh negative?
Individuals who lacks the RHD gene and does not express D-antigen on their RBC surfaces.
What is Cw antigen?
High frequency Rh antigen, rather than an allele of the C antigen.
What is G antigen?
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.
What is weak D?
Individuals who inherit a gene that is not effective in forming D-antigen due to abnormal expression of RHD gene.
What blood should weak D patients be transfused with?
Females: Rh-negative blood
Males: Rh-positive blood
What is partial D?
Individuals who have an absence of certain D-antigen epitopes and will produce antibodies against the missing epitopes.
What is Rh-null?
- 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.
What are Rh antibodies?
- 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.
What is the role of RH in HTR?
- IgG antibodies cause extravascular haemolysis.
- There are many antigens on the red cell membrane thus sensitization is effective and causes a severe of HTR.
What is the role of RH in HDFN?
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.
