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Blood type

2007 Schools Wikipedia Selection. Related subjects: Health and medicine

   Blood type is determined, in part, by the ABO blood group antigens
   present on red blood cells
   Enlarge
   Blood type is determined, in part, by the ABO blood group antigens
   present on red blood cells

   A total of 29 human blood group systems are recognized by the
   International Society of Blood Transfusion (ISBT). The most important
   of these are the ABO blood group system and the Rhesus blood group
   system.

   Each blood group is represented by a substance on the surface of red
   blood cells (RBCs). These substances are important because they contain
   specific sequences of amino acid and carbohydrate which are antigenic.
   As well as being on the surface of RBCs, some of these antigens are
   also present on the cells of other tissues. A complete blood type
   describes the 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; usually only the ABO blood group system and the
   presence or absence of the Rhesus D antigen (also known as the Rhesus
   factor) are determined and used to describe the blood type. Over 600
   different blood group antigens have been found, many of these being
   very rare. If an individual is exposed to a blood group antigen that is
   not recognised as self, the individual can become sensitized to that
   antigen; the immune system makes specific antibodies which binds
   specifically to a particular blood group antigen and an immunological
   memory against that particular antigen is formed. 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. Knowledge of an individual's
   blood type is important to identify appropriate blood for transfusion
   or tissue for organ transplantation.

   Several different RBC surface antigens stemming from one allele (or
   very closely linked genes) are collectively labeled as a blood group
   system (or blood group). The two most important blood group systems
   were discovered during early experiments with blood transfusion, the
   ABO group in 1901 and the Rhesus group in 1937. These two blood groups
   are reflected in the common nomenclature A positive, O negative, etc.
   with letters referring to the ABO group and positive/negative to the
   presence/absence of the RhD antigen of the Rhesus group. Development of
   the Coombs test in 1945 and the advent of transfusion medicine led to
   discovery of more blood groups. The Coombs test is used routinely in
   the screening of blood for blood group antibodies in the preparation of
   blood for transfusion.

   Blood types are inherited and represent contributions from both
   parents. Some blood types are rare, and are primarily found in certain
   ethnic groups. Some blood types are associated with inheritance of
   other diseases, for example the Kell antigen is associated with McLeod
   syndrome. Certain blood types may affect susceptibility to infections,
   an example being the resistance to specific malaria species seen in
   individuals lacking the Duffy antigen. Very rarely, a person's blood
   type changes through addition or suppression of an antigen in infection
   or malignancy. Transfusion reactions can occur if a person is
   transfused with blood of a different blood type. Mismatches 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.

   Often, pregnant women carry a fetus with a different blood type to
   their own, and sometimes the mother forms antibodies against the red
   blood cells of the fetus, which causes hemolysis of fetal RBCs and
   leads to low fetal blood counts, a condition known as hemolytic disease
   of the newborn.

Introduction

   ABO blood group system - diagram showing the carbohydrate chains which
   determine the ABO blood group
   Enlarge
   ABO blood group system - diagram showing the carbohydrate chains which
   determine the ABO blood group

ABO and Rhesus: the two main blood group systems

   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 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 replaced by 0
   (zero/null) in other languages.

   The Rhesus system is the second most important blood group system in
   human blood transfusion. The most important Rhesus antigen is the RhD
   antigen because it is the most immunogenic of the five main rhesus
   antigens; however, anti-RhD antibodies are not usually produced by
   sensitization against environmental substances. It is common for RhD
   negative individuals not to have any anti-RhD IgG or IgM antibodies;
   nevertheless, RhD negative individuals can produce IgG antibodies when
   they are transfused with RhD positive RBCs.

   The agglutination of IgM is stronger due to the relatively large size
   of the IgM antibody, but the nature of the bodily reaction as a result
   of agglutination with IgG can be more dramatic

Table of ABO and Rh distribution by nation

   CAPTION: ABO and Rh blood type distribution by nation (averages for
   each population)

    Population   O+    A+    B+    AB+   O−   A−   B−   AB−
    Australia   40%   31%   8%    2%    9%   7%   2%   1%
      Canada    39.0% 36.0% 7.6%  2.5%  7.0% 6.0% 1.4% 0.5%
     Denmark    35%   37%   8%    4%    6%   7%   2%   1%
     Finland    27%   38%   15%   7%    4%   6%   2%   1%
      France    36%   37%   9%    3%    6%   7%   1%   1%
   Korea, South 27.4% 34.4% 26.8% 11.2% 0.1% 0.1% 0.1% 0.05%
      Sweden    32%   37%   10%   5%    6%   7%   2%   1%
        UK      37%   35%   8%    3%    7%   7%   2%   1%
       USA      38%   34%   9%    3%    7%   6%   2%   1%

Other human blood group systems

   The International Society of Blood Transfusion currently recognizes 29
   blood group systems (including the ABO and Rh systems). 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), Le^a or Le^b positive (Lewis
   system), and so on for each blood group system. Many of the blood group
   systems were named after the patients in whom the corresponding
   antibodies were initially encountered.

Importance for transfusions

   Transfusion medicine is a specialized branch of hematology that is
   concerned with the study of blood group antigens and blood group
   antibodies, along with the work of a blood bank to provide a
   transfusion service for blood and other blood products. Across the
   world blood products must be prescribed by a medical doctor (licensed
   physician or surgeon) in a similar way to medicines. In the USA blood
   products are tightly regulated by the Food and Drug Administration.

   Blood transfusions between donor and recipient of incompatible blood
   types can cause severe acute immunological reactions, hemolysis (RBC
   destruction), renal failure, shock, and sometimes death. Antibodies can
   be highly active and can attack RBCs and bind components of the
   complement system to cause massive hemolysis of the transfused blood.

Hemolytic disease of the newborn

   An antenatal woman can make IgG blood group antibodies if her fetus has
   a blood group antigen that she does not. This can happen if some of the
   fetus' blood cells pass into the mother's blood circulation (e.g. a
   small fetomaternal hemorrhage at the time of child birth) or sometimes
   after a therapeutic blood transfusion. This can lead to Rh disease or
   another forms of hemolytic disease of the newborn (HDN) in her current
   baby or in subsequent pregnancies. Some blood groups can cause severe
   HDN, some can only cause mild HDN and others are not known to cause
   HDN.

Compatibility

Blood products

   In order to provide maximum benefit from each blood donation and to
   extend shelf-life, blood banks fractionate whole blood into several
   products. The most common of these products are packed RBCs, plasma,
   platelets, cryoprecipitate, and fresh frozen plasma (FFP). FFP is
   quick-frozen to retain labile clotting factors V and VIII and usually
   administered to patients who have a potentially fatal clotting problem
   caused by a condition such as advanced liver disease, overdose of
   anticoagulant, or disseminated intravascular coagulation (DIC).

   Clotting factors synthesized by modern recombinant methods are now in
   routine clinical use for hemophilia, as the risks of infection
   transmission that occur with pooled blood products are avoided.

Cross matching blood

   Patients should ideally receive their own blood or type-specific blood
   products to minimize the chance of a transfusion reaction. If time
   allows, the risk will further be reduced by cross-matching blood, in
   addition to blood typing both recipient and donor. Cross-matching
   involves mixing a sample of the recipient's blood with a sample of the
   donor's blood and checking to see if the mixture agglutinates, or forms
   clumps. Blood bank technicians usually check for agglutination with a
   microscope, and if it occurs, that particular donor's blood cannot be
   transfused to that particular recipient. Blood transfusion is a
   potentially risky medical procedure and it is vital that all blood
   specimens are correctly identified, so in cross-matching labeling is
   standardized using a barcode system known as ISBT 128.

RBC compatibility

     * Blood group AB individuals have both A and B antigens on the
       surface of their RBCs, and their blood serum does not contain any
       antibodies against either A or B antigen. Therefore, an individual
       with type AB blood can receive blood from any group (with AB being
       preferable), but can only donate blood to another group AB
       individual.
     * Blood group A individuals have the A antigen on the surface of
       their RBCs, and blood serum containing IgM antibodies against the B
       antigen. Therefore, a group A individual can only receive blood
       from individuals of groups A or O (with A being preferable), and
       can donate blood to individuals of groups A or AB.
     * Blood group B individuals have the B antigen on their surface of
       their RBCs, and blood serum containing IgM antibodies against the A
       antigen. Therefore, a group B individual can only receive blood
       from individuals of groups B or O (with B being preferable), and
       can donate blood to individuals of groups B or AB.
     * Blood group O (or blood group zero in some countries) individuals
       do not have either A or B antigens on the surface of their RBCs,
       but their blood serum contains IgM antibodies against both A and B
       antigens. Therefore, a group O individual can only receive blood
       from a group O individual, but they can donate blood to individuals
       of any ABO blood group (ie A, B, O or AB). O- is therefore used
       when an emergency transfusion is necessary and there has not been
       enough time to verify the patient's blood type.

   Donors of blood type O can give to A, B & AB; donors of types A & B can
   give to AB.
   Enlarge
   Donors of blood type O can give to A, B & AB; donors of types A & B can
   give to AB.

   CAPTION: RBC compatibility table

   Recipient blood type  Donor must be
           AB+          Any blood type
           AB-          O- A- B- AB-
            A+          O- O+ A- A+
            A-          O- A-
            B+          O- O+ B- B+
            B-          O- B-
            O+          O- O+
            O-          O-

   An RhD negative patient (who has not been sensitized to RhD positive
   RBCs and who does not have any anti-D antibodies) can receive RhD
   positive blood cells, but there is a high probability that this would
   sensitize the patient to the RhD antigen, and a female patient would
   risk HDN. Therefore RhD positive blood is never given to RhD negative
   women of childbearing age, and is only given to other RhD negative
   patients in extreme circumstances, such as a major bleed when RhD
   negative red cells are running short. If a RhD negative patient has
   developed anti-D antibodies, a second exposure to RhD positive blood
   would lead to a potentially dangerous transfusion reaction.
   Occasionally, for transfusion of males or women above child-bearing
   age, RhD positive blood is given to a RhD negative individual (who do
   not have atypical red cell antibodies) when it is necessary to conserve
   RhD negative blood stocks in the blood bank for use in people where
   sensitisation to RhD antigens could cause serious problems. The
   converse is not true: RhD positive patients do not react to RhD
   negative blood.

Plasma compatibility

   Plasma from type AB can be given to A, B & O; plasma from types A & B
   can be given to O.
   Enlarge
   Plasma from type AB can be given to A, B & O; plasma from types A & B
   can be given to O.

   Donor-recipient compatibility for blood plasma is the reverse from that
   of RBCs. Plasma extracted from type AB blood can be transfused to
   individuals of any blood group, but type O plasma can only be used by
   type O recipients.

   Rhesus D antibodies are not usually naturally occurring, so generally
   both RhD negative and RhD positive blood do not contain anti-RhD
   antibodies. RhD negative or RhD positive donor blood plasma can
   therefore generally be transfused into both RhD negative and RhD
   positive recipients. Consequently RhD positive or RhD negative is
   irrelevant in the table below. If anti-RhD antibodies have developed in
   a donor these would be detected by antibody screening in the blood
   bank. Donor blood containing anti-RhD antibodies would not be suitable
   for transfusion into a RhD positive patient, but anyone with any strong
   atypical blood group antibodies would not be accepted as a blood donor.

   CAPTION: Plasma compatibility table

   Recipient blood type Donor must be
            AB               AB
            A              A or AB
            B              B or AB
            O           Any blood type

Universal donors and universal recipients

   Individuals with blood type O negative are often called universal
   donors and individuals with type AB positive blood are called universal
   recipients, but the terms universal donor and universal recipient are
   not very useful, because they only consider the reaction of the
   patient's antibodies to received red blood cells, and not the
   antibodies present in the transfused blood. These terms may be
   generally true for transfusions of packed red cells, where as much of
   the plasma as possible has been removed. Thus, although a transfusion
   of O negative blood to a patient of blood group A or B is unlikely to
   produce an immune reaction due to the recipient's antibodies, the
   transfused blood may itself contain antibodies to the patient's A and B
   antigens; this can cause an adverse reaction, although the risk is far
   less than that of an O negative patient receiving types A or B. For
   this reason an exact ABO-type match is preferable where circumstances
   allow. Additionally, the other red blood cell surface antigens that
   belong to blood groups other than the ABO blood group system might
   cause an adverse reaction if they can bind the corresponding
   antibodies.

   With respect to transfusions of plasma this situation is reversed. Type
   O plasma can only be given to O recipients, while AB plasma (which does
   not contain anti-A or anti-B antibodies) can be given to patients of
   any ABO blood group.

   Transfusions are further complicated because platelets and white blood
   cells (WBCs) have their own systems of surface antigens. Sensitization
   to platelet or WBC antigens can occur as a result of transfusion.
   Retrieved from " http://en.wikipedia.org/wiki/Blood_type"
   This reference article is mainly selected from the English Wikipedia
   with only minor checks and changes (see www.wikipedia.org for details
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