Blood transfusion can be the "gift of life". To treat illness and blood loss, exchange of blood between individuals has been done for centuries, often with disastrous and fatal results. We have learned that all blood is not identical. For successful transfusion, the blood "types" of the donor and recipient must be determined and matched. Commonly called a "type and cross"

The blood TYPE refers to the particular kind of ANTIGEN present on the plasma membrane of the red blood cell. An antigen is a molecular agent that stimulates the immune system to produce ANTIBODIES. In blood typing, the antigen of interest is on the red blood cell, these markers allow your immune system to distinguish your cells from foreign cells, such as those from another person's blood or invading microorganisms. If foreign cells enter your body, their surface markers (antigens) stimulate your immune system to produce antibodies.

An antibody is a plasma protein molecule made by special lymphocytes. An antibody binds to a specific foreign antigen (in blood typing agglutination occurs) and neutralizes its danger. We use these properties to "type and cross" blood for successful transfusions in which the antigens and antibodies of the donor's blood are compatible with those of the recipient's blood.

The ABO and Rh system are the basis for blood typing. Read page 292, blood typing, in your lab manual and note Fig. 29.9 on pg. 293. Review the attached figures.

ABO blood types are determined by A or B antigens on red blood cells. Blood types A, B, and AB contain the A, B, and AB antigens respectively. Blood type O contains neither A or B antigens. The blood plasma of each blood type contains antibodies to the A and B antigens NOT found on the red blood cells.

Transfusion with incorrectly matched blood can have fatal consequences. For example, when a donor with type A blood (A antigens on RBCs) gives blood to a type B person (A antibodies or anti-A in the plasma). As the donor's type a RBCs enter the type B recipient, the donor's A antigen will react with the A antibodies in the recipient's plasma. Such an antigen-antibody reaction will cause the donors RBCs to clump together. These clumps could cause plugging of the circulatory system and tissue anoxia..not a very good thing.

Blood type AB is called the UNIVERSAL RECIPIENT. Individuals with this blood type can receive all ABO blood types, since they have neither A or B antibodies in their plasma. In contrast, people with blood type O are called UNIVERSAL DONORS because they can donate their blood to all ABO blood types. Their red blood cells do not have A and B antigens, and so an antigen-antibody reaction will not occur with A or B antibodies in the plasma of the recipient. (Source: Human Biology)

Be able to understand and interpret ABO slide typing as shown in you Lab test on pg. 293.

The A and B antigens are not the only protein antigens on the RBC surface that are important in blood transfusions. The Rh + or - abbreviation is also involved. A person who inherits the gene to make this protein antigen is said to be Rh-positive, (Rh+), while a person without this gene cannot make the Rh antigen and is said to be Rh negative (Rh-).

Rh positive individuals do not produce Rh antibodies, because doing so would lead to an antigen-antibody reaction. Rh negative individuals do not naturally have Rh antibodies, but are capable of producing them when stimulated to do so. Stimulation can occur when an Rh negative individual receives blood from an Rh positive donor. The Rh antigen on the donor's RBCs will stimulate the recipients immune system to make Rh antibodies.

An Rh negative person receiving a first transfusion with Rh positive blood doses not usually have an antigen-antibody reaction because it takes 1 to 2 months for the immune system to produce sufficient Rh antibodies. However, the recipient is now said to be sensitized, and subsequent transfusions may cause a problem. There will be an immediate antigen-antibody reaction causing the donor's RBCs to clump (as in ABO incompatibility) possibly resulting in death.

Special problems associated with Rh can occur during pregnancy. If an Rh- woman becomes pregnant by an Rh+ man, there is a chance the fetus will be Rh+. During pregnancy or childbirth, some of the fetal RBCs may leak into the mother's blood stream. If they do, her body will produce antibodies against Rh, she becomes sensitized. If she becomes pregnant again, Rh antibodies will enter the blood stream of this new fetus. If its blood type is Rh+, maternal antibodies will cause fetal RBCs to swell and burst.

In extreme cases of this disorder, called hemolytic disease of the newborn, too many RBCs are destroyed and the fetus dies (erythroblastosis fetalis).

Currently, a known Rh- woman can be treated after her first pregnancy (or spontaneous or induced abortion) with an anti-Rh gamma globulin (RhoGam) that will protect her next fetus. The drug will inactivate any fetal Rh+ cells before she can produce anti-Rh antibodies.

Be able to understand and interpret Rh typing.

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