Blood type

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Blood type
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This article is about human blood types (or blood groups). For animal
blood types, see blood type (non-human).

Blood type (or blood group) is determined, in part, by the ABO blood
group antigens present on red blood cells.A blood type (also called a
blood group) is a classification of blood based on the presence or
absence of inherited antigenic substances on the surface of red blood
cells (RBCs). These antigens may be proteins, carbohydrates,
glycoproteins, or glycolipids, depending on the blood group system,
and some of these antigens are also present on the surface of other
types of cells of various tissues. Several of these red blood cell
surface antigens, that stem from one allele (or very closely linked
genes), collectively form a blood group system.[1]

Blood types are inherited and represent contributions from both
parents. A total of 29 human blood group systems are now recognized by
the International Society of Blood Transfusion (ISBT).[2]

Many pregnant women carry a fetus with a different blood type from
their own, and the mother can form antibodies against fetal RBCs.
Sometimes these maternal antibodies are IgG, a small immunoglobulin,
which can cross the placenta and cause hemolysis of fetal RBCs, which
in turn can lead to hemolytic disease of the newborn, an illness of
low fetal blood counts which can be temporary or treatable, but can
occasionally be severe.

Contents [hide]
1 Serology
2 ABO and Rh blood grouping
3 Blood group systems
3.1 ABO blood group system
3.2 Rhesus blood group system
3.3 ABO and Rh distribution by country
3.4 Other blood group systems
4 Clinical significance
4.1 Blood transfusion
4.2 Hemolytic disease of the newborn (HDN)
5 Compatibility
5.1 Blood products
5.2 Red blood cell compatibility
5.3 Plasma compatibility
5.4 Universal donors and universal recipients
6 Conversion
7 History
8 Cultural beliefs regarding blood types
9 References
10 Further reading



[edit] Serology
If an individual is exposed to a blood group antigen that is not
recognised as self, the immune system will produce antibodies that can
specifically bind to that particular blood group antigen, and an
immunological memory against that antigen is formed. The individual
will have become sensitized to that blood group antigen. These
antibodies can bind to antigens on the surface of transfused red blood
cells (or other tissue cells), often leading to destruction of the
cells by recruitment of other components of the immune system. When
IgM antibodies bind to the transfused cells, the transfused cells can
clump. It is vital that compatible blood is selected for transfusions
and that compatible tissue is selected for organ transplantation.
Transfusion reactions involving minor antigens or weak antibodies may
lead to minor problems. However, more serious incompatibilities can
lead to a more vigorous immune response with massive RBC destruction,
low blood pressure, and even death.


[edit] ABO and Rh blood grouping
The corresponding antibodies to the RBC surface antigens of the ABO
blood group system are sometimes called "naturally occurring". This
means that people who are blood type A will have Anti-B. The theory
that explains how these antibodies are developed states that antigens
similar to the A and B antigens occur in nature, including in food,
plants and bacteria. After an infant is born, the gut become colonized
with normal flora which express these A and B-like antigens, causing
the immune system to make antibodies to those antigens that the red
cells do not possess. So, people who are blood type A will have Anti-
B, blood type B will have Anti-A, blood type O will have both Anti-A
and Anti-B, and blood type AB will have neither. Because of these so
called "naturally occurring" and expected antibodies, it is important
to correctly determine a patient's blood type prior to transfusion of
any blood component. These naturally occurring antibodies are of the
IgM class, which have the capability of agglutinating (clumping) and
damaging red cells within the blood vessels, possibly leading to
death. It is not necessary to determine any other blood groups because
almost all other red cell antibodies can only develop through active
immunization, which can only occur through either previous blood
transfusion or pregnancy. A test called the Antibody Screen is always
performed on patients who may require red blood cell transfusion, and
this test will detect most clinically significant red cell antibodies.

The RhD antigen is also important in determining a person's blood
type. The terms "positive" or "negative" refer to either the presence
or absence of the Rh or D antigen. Anti-D is not usually a naturally
occurring antibody as the Anti-A and Anti-B antibodies are, but
matching for the D antigen is considered extremely clinically
important. The D antigen is immunogenic, meaning that a person who is
D negative is very likely to make Anti-D when exposed to the D antigen
(through either transfusion or pregnancy). Once this antibody is made,
D negative blood must always be given. The Anti-D antibody is also
known to be the cause for one of the most severe forms of hemolytic
disease of the newborn (HDN). HDN, due to Anti-D antibody produced by
a D negative mother, can cause severe anemia in the fetus and can
possibly lead to fetal demise. Prevention of the formation of Anti-D
by D negative mothers is accomplished by a medication called Rho(D)
immune globulin, given at about 28 weeks of gestation and after
delivery, if the infant is determined to be D positive.


[edit] Blood group systems
A total of 29 human blood group systems are now recognized by the
International Society of Blood Transfusion (ISBT).[2] A complete blood
type would describe a full set of 29 substances on the surface of
RBCs, and an individual's blood type is one of the many possible
combinations of blood group antigens. Across the 29 blood groups, over
600 different blood group antigens have been found,[3] but many of
these are very rare or are mainly found in certain ethnic groups.

Almost always, an individual has the same blood group for life; but
very rarely an individual's blood type changes through addition or
suppression of an antigen in infection, malignancy or autoimmune
disease.[4][5][6][7] An example of this rare phenomenon is the case
Demi-Lee Brennan, an Australian citizen, whose blood group changed
after a liver transplant.[8][9] Another more common cause in blood
type change is a bone marrow transplant. Bone marrow transplants are
performed for many leukemias and lymphomas, among other diseases. If a
person receives a bone marrow from someone who is a different ABO type
(ex. a type A patient receives a type O bone marrow), the patient's
blood type will eventually convert to the donor's type.

Some blood types are associated with inheritance of other diseases;
for example, the Kell antigen is sometimes associated with McLeod
syndrome.[10] Certain blood types may affect susceptibility to
infections, an example being the resistance to specific malaria
species seen in individuals lacking the Duffy antigen.[11] The Duffy
antigen, presumably as a result of natural selection, is less common
in ethnic groups from areas with a high incidence of malaria.[12]


[edit] ABO blood group system

ABO blood group system - diagram showing the carbohydrate chains which
determine the ABO blood groupMain article: ABO blood group system
The ABO system is the most important blood group system in human blood
transfusion. The associated anti-A antibodies and anti-B antibodies
are usually "Immunoglobulin M", abbreviated IgM, antibodies. ABO IgM
antibodies are produced in the first years of life by sensitization to
environmental substances such as food, bacteria and viruses. The "O"
in ABO is often called "0" (zero/null) in other languages.[13]

Phenotype Genotype
A AA or AO
B BB or BO
AB AB
O OO


[edit] Rhesus blood group system
Main article: Rhesus blood group system
The Rhesus system is the second most significant blood group system in
human blood transfusion. The most significant Rhesus antigen is the
RhD antigen because it is the most immunogenic of the five main rhesus
antigens. It is common for RhD negative individuals not to have any
anti-RhD IgG or IgM antibodies, because anti-RhD antibodies are not
usually produced by sensitization against environmental substances.
However, RhD negative individuals can produce IgG anti-RhD antibodies
following a sensitizing event: possibly a fetomaternal transfusion of
blood from a fetus in pregnancy or occasionally a blood transfusion
with RhD positive RBCs.


[edit] ABO and Rh distribution by country
ABO and Rh blood type distribution by nation (averages for each
population) Country O+ A+ B+ AB+ O- A- B- AB-
Austria[14] 30% 33% 12% 6% 7% 8% 3% 1%
Australia[15] 40% 31% 8% 2% 9% 7% 2% 1%
Belgium[16] 38.1% 34% 8.5% 4.1% 7% 6% 1.5% 0.8%
Canada[17] 39% 36% 7.6% 2.5% 7% 6% 1.4% 0.5%
Denmark[18] 35% 37% 8% 4% 6% 7% 2% 1%
Finland[19] 27% 38% 15% 7% 4% 6% 2% 1%
France[20] 36% 37% 9% 3% 6% 7% 1% 1%
Germany[21] 35% 37% 9% 4% 6% 6% 2% 1%
Hong Kong, China[22] 40% 26% 27% 7% <0.3% <0.3% <0.3% <0.3%
Ireland[23] 47% 26% 9% 2% 8% 5% 2% 1%
Korea, South[24] 27.2% 35.1% 26.1% 11.3% 0.1% 0.1% 0.1% 0.05%
Netherlands[25] 39.5% 35% 6.7% 2.5% 7.5% 7% 1.3% 0.5%
New Zealand[26] 38% 32% 9% 3% 9% 6% 2% 1%
Poland[27] 31% 32% 15% 7% 6% 6% 2% 1%
Sweden[28] 32% 37% 10% 5% 6% 7% 2% 1%
UK[29] 37% 35% 8% 3% 7% 7% 2% 1%
USA[30] 37.4% 35.7% 8.5% 3.4% 6.6% 6.3% 1.5% 0.6%


[edit] Other blood group systems
Main article: Human blood group systems
The International Society of Blood Transfusion currently recognizes 29
blood group systems (including the ABO and Rh systems).[2] Thus, in
addition to the ABO antigens and Rhesus antigens, many other antigens
are expressed on the RBC surface membrane. For example, an individual
can be AB RhD positive, and at the same time M and N positive (MNS
system), K positive (Kell system), Lea or Leb negative (Lewis system),
and so on, being positive or negative for each blood group system
antigen. Many of the blood group systems were named after the patients
in whom the corresponding antibodies were initially encountered.