BLOOD TYPING AND TRANSFUSION
Blood typing is the method of determining what blood type do you have, based on the presence or absence of antigens on your red cells. There are more than 20 genetically determined blood group systems known today, the most important being ABO blood grouping and Rh blood grouping. It is important that each person knows his own blood type. This is especially helpful when one needs emergency transfusion (the process of receiving blood) in case of accident or surgery, or when a loved one needs blood of the same type.
ABO Blood Typing
ABO blood typing was discovered by Karl Landsteiner in 1901. Blood is classified as: Type A, Type B, Type AB or Type O.
If you are Type A, this means you have the A antigen on the surface of your red blood cell. This also means you have the anti-B antibody in your plasma (the liquid portion of the blood). If you are Type B, this means you have the B antigen on the surface of your red blood cell. This also means you have anti-A antibody in your plasma. If you are Type AB, this means you have both A antigen and B antigen on the surface of your red cell. This also means you do not have anti-A nor anti-B antibody in your plasma. If you are Type O, this means you do not have A antigen nor B antigen on the surface of your red cell. Likewise, this also means you have anti-A and anti-B antibodies in your plasma.
Type O persons are considered universal donors because of the absence of A antigen and B antigen on their red cells which may react with the recipient�s antibodies. Type AB persons are considered universal recipients because of the absence of anti-A and anti-B antibodies in their plasma which may react with the donor�s red cell antigens. In cases of extreme emergency when it is critical to give blood immediately, Type O blood, preferably Rh-negative, is considered safe if the person�s (recipient) blood type is not known. However, the safest blood is still one�s own type.
Expected Reactions :
When blood typing is performed, if your red cells stick together when mixed with Anti-A serum, then you are Type A. If your red cells stick together when mixed with Anti-B serum, then you are Type B. If your red cells stick together when mixed with both Anti-A and Anti-B serums, then you are Type AB. However, if your red cells do not stick together when mixed with Anti-A and Anti-B serums, then you are Type O.
Rh Blood Typing
Rh blood type is also another important blood grouping because of the highly-reactive Rh antigen. Rh blood grouping was discovered in 1937 by Landsteiner and Wiener, following their experiments which showed that rabbits, when injected blood from rhesus monkey, produced antibody that agglutinated with red blood cells of many humans.
Most people are Rh(+). Among whites, 15% are Rh (-); among blacks, 10% are Rh (-). Rh(+) individuals do not have anti-Rh antibodies. But Rh(-) individuals, when exposed to Rh antigen, will develop anti-Rh antibodies and this may be fatal, such as in the case of Rh(-) mothers who gave birth to an Rh(+) baby and is pregnant with the next baby who is Rh(+). The exposure of blood due to placental rupture during delivery will trigger production of Rh antibodies in the mother�s plasma. Anti-Rh antibodies already in the mother�s plasma upon the second pregnancy may pass through the placenta and react with the fetus� Rh antigen (assuming the fetus is Rh(+).) To avoid this, an Rh(-) mother is given Rh immune globulin around 28th week of pregnancy and within 72 hours after delivery of an Rh(+) baby, to prevent production of anti-Rh antibodies in her (mother�s) plasma.
Expected Reactions :
When blood typing is performed, if your red cells stick together when mixed with Anti-Rh serum, then you have an Rh-positive blood. On the other hand, if your red cells do not stick together when mixed with Anti-Rh serum, then you have an Rh-negative blood.
Blood Transfusion
Transfusion of blood does not only test for compatible blood type of recipient and donor (Type A patient must receive blood from Type A donor; Type B patient must receive blood from Type B donor; Type AB patient must receive blood from Type AB donor; and Type O patient must receive blood from Type O donor.). The donated blood is also tested for infectious diseases that may harm the recipient. Tests include testing for Hepatitis B and C, HIV and Treponema pallidum (causative agent of syphilis).
Prior to transfusion, crossmatching of blood is done to check for agglutination (clumping of blood) or hemolysis (lysis or red cells) of donor�s red cells with the patient�s serum. This is called major crossmatching. Crossmatching can also detect minor antigens which are not routinely detected during blood typing. A minor crossmatching may also be performed to check for agglutination of the patient�s red cells with the donor�s serum. Absence of agglutination or hemolysis means there is no antigen-antibody reaction, and therefore transfusion of donor blood can proceed.
We are fortunate that discoveries in medicine paved the way for safe transfusion to be performed nowadays. The discoveries of the different blood groups have made us aware of the importance of transfusion of similar blood type that is compatible and safe. It is such a far accomplishment compared to centuries ago when people had experimented, but failed and lost lives in the process, using animal blood yet to transfuse to humans and using human blood but without the knowledge of blood type compatibility.
(References: MedlinePlus Medical Encyclopedia, HealthAtoZ.com, Nobelprize.org, Wikipedia.org, The Blood Handbook)