Blood typing - ABO blood groups and Rh types
ABO blood group system, the classification of human blood based on the inherited hemorrhage is present and transfusion of Rh-positive blood is lifesaving. In contrast to the ABO group, anti-D antibodies that react against D antigens are not usually present in the blood under. Jul 21, Your blood group is a combination of the ABO system and the Rh system: If the red blood cell has B antigen only, that blood is called "type B".
It is typically caused by a single amino acid switch in the transmembrane region of the RhD protein.
In most cases, adequate levels of D antigen are present and because there has been no change in D epitopes, the formation of anti-D is prevented. Therefore, individuals with the weak D phenotype can receive Rh D-positive blood.
The hybrid protein is similar enough to RhD to be correctly inserted in the RBC membrane, but it lacks several epitopes found on the complete RhD protein. If a person with the partial D phenotype encounters the complete D antigen on transfused RBCs, they may form anti-D and suffer from a transfusion reaction. This complex is only expressed in cells of the erythroid line, and therefore Rh antigens are only expressed in RBCs.
The composition of the complex is unknown, but it is thought to be a tetramer, consisting of two molecules of Rh-associated glycoprotein RhAG and two molecules of Rh proteins. If it is missing, none of the Rh antigens are expressed.
ABO blood group system | Definition, Blood Type, & ABO Antigens | dayline.info
However, it is not polymorphic and does not carry Rh antigens itself 3. The absence of the Rh complex alters the RBC shape, increases its osmotic fragility, and shortens its lifespan, resulting in a hemolytic anemia that is usually mild in nature.
These patients are at risk of adverse transfusion reactions because they may produce antibodies against several of the Rh antigens. Rh antigens may also be involved in the transport of ammonium across the RBC membrane. Interestingly, the first member of a family of water channels aquaporins and the first member of a family of urea transporters were both found in blood group proteins the Colton blood group and Kidd blood group, respectively.
Clinical significance of Rh antibodies The Rh antigens are highly immunogenic, and most of the Rh antibodies should be considered as potential causes of hemolytic transfusion reactions and HDN.
ABO blood group system
This large difference in amino acids is the reason why the Rh antigens are potent at stimulating an immune response 4. The majority of antibodies formed against the Rh antigens are of the IgG type. Rh antibodies rarely, if ever, bind complement, and therefore RBC destruction is mediated almost exclusively via macrophages in the spleen extravascular hemolysis. There are a few examples of Rh alloantibodies that are naturally occurring and are of the IgM type, but they are in the minority.
Transfusion reactions Anti-D, anti-C, anti-E, and anti-e have all been involved in hemolytic transfusion reactions, particularly delayed reactions 5.
ABO blood group system - Wikipedia
Routine blood typing for Rh D status in both blood donors and transfusion recipients has reduced the incidence of transfusion reactions caused by anti-D. But sensitization to other Rh antigens can be a problem in transfusion medicine, particularly in patients with sickle cell anemia SCA. Blacks are also more likely to express variants of the Rh e antigen, and therefore produce anti-e, along with other Rh alloantibodies, which increases the difficulty in finding Rh-compatible blood donors.
Hemolytic disease of the newborn Anti-D causes the most severe form of HDN and it used to be a major cause of fetal death.
Since the introduction of anti-D immunoglobulin along with careful monitoring of at-risk pregnancies, the prevalence of HDN because of Rh D incompatibility has decreased dramatically. However, all cases cannot be prevented, and RhD alloimmunization remains a major cause of disease 6. Other Rh alloantibodies that are capable of causing severe HDN include anti-c 7, 8which clinically is the most important Rh antigen after the D antigen. Blood type distribution by country The distribution of the blood groups A, B, O and AB varies across the world according to the population.
There are also variations in blood type distribution within human subpopulations. In the UK, the distribution of blood type frequencies through the population still shows some correlation to the distribution of placenames and to the successive invasions and migrations including NorsemenDanesSaxonsCeltsand Normans who contributed the morphemes to the placenames and the genes to the population.
A premature stop codon results from this frame-shift mutation. This variant is found worldwide, and likely predates human migration from Africa.
The O01 allele is considered to predate the O02 allele. The continued presence of the O alleles is hypothesized to be the result of balancing selection.
The antibodies created against these environmental antigens in the first years of life can cross-react with ABO-incompatible red blood cells that it comes in contact with during blood transfusion later in life.
The overall change in reaction times was always larger in the RhD-negative group than in the RhD-positive. Origin of RHD polymorphism[ edit ] This section possibly contains original research. Please improve it by verifying the claims made and adding inline citations. Statements consisting only of original research should be removed.
- Blood typing
December Learn how and when to remove this template message For a long time, the origin of RHD polymorphism was an evolutionary enigma. RhD-negative women in a population of RhD positives or RhD-positive men in a population of RhD negatives were at a disadvantage as some of their children RhD-positive children born to preimmunised RhD-negative mothers were at a higher risk of fetal or newborn death or health impairment from hemolytic disease.
It was suggested that higher tolerance of RhD-positive heterozygotes against Toxoplasma -induced impairment of reaction time   and Toxoplasma-induced increase of risk of traffic accident  could counterbalance the disadvantage of the rarer allele and could be responsible both for the initial spread of the RhD allele among the RhD-negative population and for a stable RhD polymorphism in most human populations.
In contrast to the situation in Africa and certain but not all regions of Asia, the abundance of wild cats definitive hosts of Toxoplasma gondii in Europe was very low before the advent of the domestic cat. Weak D[ edit ] In serologic testing, D positive blood is easily identified.
Rh blood group system
Units which are D negative are often retested to rule out a weaker reaction. This was previously referred to as Du, which has been replaced. Weak D phenotype can occur in several ways. In some cases, this phenotype occurs because of an altered surface protein that is more common in people of European descent.