Discover

The term 'Rhesus blood group system' refers to the five main Rhesus antigens (C, c, D, E and e) as well as the many other less frequent Rhesus antigens. The terms 'Rhesus factor' and 'Rh factor' are equivalent and refer to the 'Rh D antigen' only.

Contents

Rhesus factor

History of discoveries

Rh nomenclature

The Rhesus system antigens

Hemolytic disease of the newborn

Population data

Inheritance

References

External links

Rhesus factor

Individuals either have, or do not have, the 'Rhesus factor' (or Rh D antigen) on the surface of their red blood cells. This is usually indicated by 'RhD positive' (does have the RhD antigen) or 'RhD negative' (does not have the antigen) suffix to the ABO blood type. This suffix is often shortened to 'D pos'/'D neg', 'RhD pos'/RhD neg', or +/-. The latter is generally not preferred in research or medical situations, because it can be altered or obscured accidentally.
There may be prenatal danger to the fetus when a pregnant woman is RhD-negative and the biological father is RhD-positive. But, as discussed below, the situation is considerably more complex than that.

History of discoveries

The Rhesus system is named after the Rhesus Macaque, following experiments by Karl Landsteiner and Alexander S. Wiener, which showed that rabbits, when immunized with rhesus monkey red cells, produce an antibody that also agglutinates the red blood cells of many humans. Landsteiner and Alexander S. Wiener discovered this factor in 1937 (publishing in 1940).^[1] The significance of the Rh factor was soon realized. Dr. Phillip Levine working at the Newark Beth Israel Hospital made a connection between the Rh factor and the incidence of erythroblastosis fetalis, and Wiener realized adverse reactions from transfusions were also resulting from the Rh factor. Wiener then pioneered the exchange transfusion to combat erythroblastosis fetalis in newborn infants. This transfusion technique saved the lives of many thousands of infants before intrauterine transfusion was invented which enabled much more severely affected fetuses to be successfully treated. Drs. Neva Abelson and L.K. Diamond co-discovered a simple test for the Rh factor which was widely applied.^[2]

Rh nomenclature

The Rhesus system has two sets of nomenclatures, one developed by Doctors Fisher and Race and one by Dr. Wiener. Both systems reflected alternate theories of inheritance. The Fisher-Race system, which is more commonly in use today, utilizes the CDE nomenclature. This system originally postulated that there are three closely linked genes on each chromosome. The genes were designated as D and its hypothetical allele d; C and its allele c, E and its allele e. Each gene was supposed to control the product of the corresponding antigen (i.e., D gene produces D antigen, etc.) However, the d gene was hypothetical, not actual.
The Wiener system used the Rh-Hr nomenclature. This system theorized that there was one gene at a single locus on each chromosome of the pair which controls production of multiple antigens. This concept postulated that a gene R gives rise to the “blood factors” Rho, rh’, and hr” and the gene r will produce hr’ and hr”.
Notations of the two theories are used interchangeably in blood banking (e.g., Rho(D)). Wiener’s notation is more complex and cumbersome for routine use. Because it is simpler to explain, the Fisher-Race theory is more widely used.
DNA testing has shown that both theories are partially correct. There are in fact two linked genes, one with multiple specificities and one with a single specificity. Thus, Wiener's postulate that a gene could have multiple specificities (something many did not give credence to originally) has been proven correct. On the other hand, Wiener's theory that there is one gene has proven incorrect, as has the Fischer-Race theory that there are three genes.

The Rhesus system antigens

The proteins which carry the Rhesus antigens are transmembrane proteins, whose structure suggest that they are ion channels. The main antigens are C, D, E, c and e, which are encoded by two gene loci, the ''D'' locus and the ''CE'' locus. There is no d antigen. Lowercase "d" indicates the absence of the D antigen (the gene is either deleted or nonfunctional).

'Rhesus genotypes'

Genotype	symbol	'Rh(D) status'
'cde/cde'	rr	Negative
'CDe/cde'	R1r	Positive
'CDe/CDe'	R1R1	Positive
'cDE/cde'	R2r	Positive
'CDe/cDE'	R1R2	Positive
'cDE/cDE'	R2R2	Positive

Hemolytic disease of the newborn

Main articles: Hemolytic disease of the newborn

Hemolytic disease of the newborn is also called Erythroblastosis Fetalis. This condition occurs when there is an incompatibility between the blood types of the mother and the baby. These terms do not indicate which specific antigen-antibody incompatibility is implicated.

★ 'hemolytic' comes from two words: 'hemo' (blood) and 'lysis' (destruction) or breaking down of red blood cells

★ 'erythroblastosis' refers to the making of immature red blood cells

★ 'fetalis' refers to the fetus
When the condition is caused by the RhD antigen-antibody incompatibility, it is called 'RhD Hemolytic disease of the newborn' (often called 'Rhesus disease' or 'Rh disease' for brevity). Here, sensitization to Rh D antigens (usually by feto-maternal transfusion during pregnancy) may lead to the production of maternal IgG anti-RhD antibodies which can pass through the placenta. This is of particular importance to RhD negative females of or below childbearing age, because any subsequent pregnancy may be affected by the Rhesus D hemolytic disease of the newborn if the baby is Rh D positive. The vast majority of Rh disease is preventable in modern antenatal care by injections of IgG anti-D antibodies (Rho(D) Immune Globulin). The incidence of Rhesus disease is mathematically related to the frequency of RhD negative individuals in a population, so Rhesus disease is rare in East Asians and Africans, but more common in Caucasians.

★ 'Symptoms and signs in the Fetus':

★
★ Enlarged liver, spleen, or heart and fluid buildup in the fetus' abdomen seen via ultrasound.

★ 'Symptoms and signs in the Newborn':

★
★ 'Anemia' which creates the newborn's pallor (pale appearance).

★
★ 'Jaundice' or yellow discoloration of the newborn's skin, sclera or mucous membrane. This may be evident right after birth or after 24 - 48 hours after birth. This is caused by bilirubin (one of the end products of red blood cell destruction).

★
★ Enlargement of the newborn's liver and spleen.

★
★ The newborn may have 'severe edema' of the entire body.

★
★ 'Dyspnea' or difficulty breathing.

Population data

The frequency of Rh factor blood types and the RhD neg allele gene differs in various populations.

'Population data for the Rh D factor and the RhD neg allele'^[3]

Population	Rh(D) Neg	Rh(D) Pos	Rh(D) Neg alleles
European Basque	approx 35%	65%	approx 60%
Caucasian	16%	84%	40%
American Blacks	approx 7%	93%	approx 26%
Native Americans	approx 1%	99%	approx 10%
African descent	less 1%	over 99%	3%
Japanese & Chinese	less 1%	over 99%	1%

Inheritance

The Rh(D) antigen is inherited on one locus (on the short arm of the first chromosome, 1p36.13-p34.3) with two alleles, of which Rh+ is dominant and Rh− recessive. The gene codes for a polypeptide on the red cell membrane. Rh− individuals (''dd'' genotype) do not produce this antigen, and may be sensitized to Rh+ blood.
The Rhesus system is much more complex than the ABO blood type system because there are more than 30 combinations possible.^[4]
Two very similar epitopes, ''Cc'' and ''Ee'', appear to be closely related to Rh.

References

1. Landsteiner K, Wiener AS. ''An agglutinable factor in human blood recognized by immune sera for rhesus blood.'' Proc Soc Exp Biol Med 1940;43:223-224.
2. Wsutoday Test for Rh factor
3.
4. Genetics of Rhesus Factor



★ Mollison PL, Engelfriet CP and Contreras M. Blood Transfusion in Clinical Medicine. 1997. 10th edition. Blackwell Science, Oxford, UK.

External links

★ Rh at BGMUT Blood Group Antigen Gene Mutation Database at NCBI, NIH