外國人最想和你聊的文化話題：你是什么血型

　Realize Blood Type　認(rèn)識血型

     1　血型及輸血
     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. 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 can stem from one allele (or very closely linked genes) and collectively form a blood group system. Blood types are inherited and represent contributions from both parents. A total of 30 human blood group systems are now recognized by the International Society of Blood Transfusion (ISBT).
     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 that ranges from mild to severe.
     Much of the routine work of a blood bank involves testing blood from both donors and recipients to ensure that every individual recipient is given blood that is compatible and is as safe as possible. If a unit of incompatible blood is transfused between a donor and recipient, a severe acute hemolytic reaction with hemolysis (RBC destruction), renal failure and shock is likely to occur, and death is a possibility. Antibodies can be highly active and can attack RBCs and bind components of the complement system to cause massive hemolysis of the transfused blood.
     Patients should ideally receive their own blood or type-specific blood products to minimize the chance of a transfusion reaction. Risks can be further reduced by cross-matching blood, but this may be skipped when blood is required for an emergency. Cross-matching involves mixing a sample of the recipient's serum with a sample of the donor's red blood cells and checking if the mixture agglutinates, or forms clumps. If agglutination is not obvious by direct vision, blood bank technicians usually check for agglutination with a microscope. If agglutination occurs, that particular donor's blood cannot be transfused to that particular recipient. In a blood bank it is vital that all blood specimens are correctly identified, so labeling has been standardized using a barcode system known as ISBT 128.
     2　血型的表達(dá)方式
     Blood group B　B型血
     Blood group B has its highest frequency in Northern India and neighboring Central Asia, and its incidence diminishes both towards the west and the east, falling to single digit percentages in Spain.It is believed to have been entirely absent from Native American and Australian Aboriginal populations prior to the arrival of Europeans in those areas.
     Blood group A　A型血
     Blood group A is associated with high frequencies in Europe, especially in Scandinavia and Central Europe, although its highest frequencies occur in some Australian Aborigine populations and the Blackfoot Indians of Montana.
     Blood group O　O型血
     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 anti-A and anti-B antibodies against the A and B blood group antigens. Therefore, a group O individual can receive blood only from a group O individual, but can donate blood to individuals of any ABO blood group (i.e., A, B, O or AB).
     Blood group AB　AB型血
     Individuals have both A and B antigens on the surface of their RBCs, and their blood plasma 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 donate blood only to another type AB individual.
     紅細(xì)胞血型是1900年由奧地利的K．蘭德施泰納發(fā)現(xiàn)的。他把每個(gè)人的紅細(xì)胞分別與別人的血清交叉混合后，發(fā)現(xiàn)有的血液之間發(fā)生凝集反應(yīng)，有的則不發(fā)生。他認(rèn)為凡是凝集者，紅細(xì)胞上有一種抗原，血清中有一種抗體。如抗原與抗體有相對應(yīng)的特異關(guān)系，便發(fā)生凝集反應(yīng)。如紅細(xì)胞上有A抗原，血清中有抗A抗體，便會發(fā)生凝集。如果紅細(xì)胞缺乏某一種抗原或血清中缺乏與之對應(yīng)的抗體，就不發(fā)生凝集。根據(jù)這個(gè)原理他發(fā)現(xiàn)了人的ABO血型。