Blood transfusion is the process which we all know is used to give blood to a person who has either lost a significant amount of blood or requires it due to a problem with his or her own. There is a fundamental prerequisite before this is done called blood typing. This is where it is decided whether one falls into one of the following blood types A, B, AB, or O. In addition to this is a rhesus factor called Rh that indicates positivity or negativity. This is important because giving the wrong type of blood to a person can result in a fatal reaction from the person’s immune system. This is because the blood types correspond to antigens and therefore are attacked by antibodies if not identified. The theory behind the existence of blood groups seems to go back into the development of community immunity.
Each of the blood types is basically an antigen or a glycoprotein on the surface of a red blood cell. This antigen can be either A, B, or AB. The presence of an antigen within the body usually signals to the body that it is part of the organism itself and not a foreign being. Therefore, if one has a blood type of A, the person’s immune system would not attack the red blood cells because there are not antibodies against it. Similarly for B; however, AB indicates that the person has both A and B antigens on the cell surface. This is a unique situation because the person can receive blood of either A or B type. O is the really interesting type here because O indicates that there are no surface antigens. This means that anybody can receive type O blood. AB people are known as universal recipients and O are known as universal donors but they can only receive blood from other O types. To add to this there is a further subdivision on Rh factor which is yet another antigen combination.
It is hypothesized that exposure at a community level to certain pathogens like viruses and bacteria will help express these antigens. Testing for a surface antigen is performed before a blood transfusion on plates that cause clumping or agglutination of red blood cells against an antibody. This test will immediately tell the doctor what blood type the person is to identify the exact blood that is needed. However, in an emergency room situation, O type blood is always kept in stock since this is the universal donor type.