Rhesus blood group system
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The term Rhesus system refers to all of the antigens of the Rhesus blood group system - the five main rhesus antigens (C, c,D, E and e) as well as many other less frequent antigens. The terms Rhesus factor and Rh factor are equivalent and refer to the Rh D antigen only.
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[edit] 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 can be indicated with a plus (+) or minus (−) suffix after the ABO blood type (ie A- or O+), but for clarity in laboratory work it is better not to use this notation, which could be changed by a smudge. For laboratory work the suffixes 'Rh D positive', 'D pos' or 'RhD pos' may be used for Rhesus D positive blood, and the suffixes 'Rh D negative', 'D neg' or 'RhD neg' may be used for Rhesus D negative blood.
[edit] History of discovery
The Rhesus system is named after the Rhesus monkey, following experiments by Karl Landsteiner and Alexander S. Wiener, which showed that rabbits, when immunised 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 tranfusions 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]
[edit] Rh nomenclature
The Rhesus system has two sets of nomenclatures, one developed by Drs. 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 reduce 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.
[edit] 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).
| 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 |
[edit] Hemolytic disease of the newborn
RhD Hemolytic disease of the newborn is often called Rhesus disease or Rh disease for brevity. Sensitization to Rh D antigens (usually by feto-maternal transfusion during pregnancy) may lead to the production 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 the Chinese, Japanese and Africans, but more common in Caucasians.
Rhc antigens can occasionally cause a severe hemolytic disease of the newborn (anti-Rhc).
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.
> 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
Some of the effects of this disease to the fetus include:
1. Enlarged liver, spleen, or heart and fluid buildup in the fetus' abdomen seen via ultrasound.
After birth, symptoms may include:
1. Anemia which creates the newborn's pallor (pale appearance).
2. 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).
3. Enlargement of the newborn's liver and spleen.
4. The newborn may have severe edema of the entire body.
5. Dyspnea or difficulty breathing.
[edit] Population data
The frequency of Rh factor blood types and the RhD neg allele gene differs in various populations.
| 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 American Indians | approx 1% | 99% | approx 10% |
| African descent | less 1% | over 99% | 3% |
| Japanese & Chinese | less 1% | over 99% | 1% |
[edit] 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.
Two very similar epitopes, Cc and Ee, appear to be closely related to Rh.
[edit] References
- ^ 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.
- ^ Wsutoday Test for Rh factor
- ^ Mack, Steve (March 21, 2001). Re: Is the RH negative blood type more prevalent in certain ethnic groups?. MadSci Network.
- Mollison PL, Engelfriet CP and Contreras M. Blood Transfusion in Clinical Medicine. 1997. 10th edition. Blackwell Science, Oxford, UK.
