 This video will cover the following objective from the Physiology of Blood Hematology, describe the ABO and RH blood groups, and how to cross-match donor blood with a recipient blood type to prevent a transfusion reaction. An antigen is any chemical structure that can stimulate an adaptive immune response. Blood type results from antigens on the surface of erythrocytes. If a patient receives a blood transfusion that contains surface antigens on the erythrocytes which are not normally found in that patient's blood, the patient's immune system will produce antibodies that can bind to the surface antigens on the donor blood and attack those erythrocytes, causing what's known as a transfusion reaction. Transfusion reactions can then lead to organ failure complications and lead to death. One of the ways that antibodies will attack erythrocytes as they bind to the surface antigens on erythrocytes, antibodies will stimulate clumping of the erythrocytes, which is known as agglutination. As these clumps of erythrocytes form in the blood, they can start to block small blood vessels and disrupt blood flow in the organ, and by disrupting blood flow to an organ, this can lead to organ failure. Emolysis refers to the breakdown of erythrocytes in the blood, and this is another mechanism contributing to lethal transfusion reactions. When a patient is given a transfusion with blood that contains antigens not normally found in their blood, their antibodies will bind to those antigens and stimulate other defense proteins called the complement proteins, which form a membrane attack complex, which punches holes in the plasma membrane, causing the cell to rupture, and when this occurs to an erythrocyte, hemoglobin spills out from the cytoplasm into the blood plasma, and then hemoglobin will damage the kidney leading to kidney failure, which contributes to the lethal effects of a transfusion reaction. So here we see a table showing the ABO blood group. If a person has type A blood, they have the A antigen on the surface of their erythrocytes, and they will produce antibodies that can bind to the B antigen, causing a transfusion reaction if they are given type B blood or type AB blood. A person with type B blood has the B antigens on the surface of their erythrocytes, and they produce antibodies that can bind to the A antigen, and so they would have a transfusion reaction if we gave them type A blood or type AB blood. Type AB blood has both the A and the B antigens on the surface of the erythrocytes, therefore a patient with type AB blood could safely receive a transfusion from type A blood, type B blood, or type O blood, as they do not produce any antibodies against the A or the B antigens. Type O blood does not have the A or the B antigens, and therefore a patient with type O blood produces antibodies against the A and the B antigens. Therefore a patient with type O blood cannot safely receive a transfusion of type A blood, type B blood, or type AB blood. However, type O blood is the universal donor because we could safely give a transfusion of type O blood to a patient who has type A blood, or type B blood, or type AB blood. In addition to the ABO blood group, there is another surface antigen on erythrocytes known as the D antigen, and the presence or absence of this D antigen gives rise to what we call the RH blood group. So RH stands for rhesus, the rhesus macaque is a monkey that was first studied in order to identify this antigen, this blood group, and you can either have the D antigen, meaning you're positive for the RH factor, or you do not have the D antigen, meaning you're negative for the RH factor. Here we see the results from a blood typing card that has three different wells in it where we place a sample of blood into the three wells. The first well has the anti-A antibodies in the well, and if we place blood in that well that has the A antigen, that blood will clump up, it will agglutinate, and that's what we can see in the image there is the blood has agglutinated. The well in the center here contains anti-B antibodies, and if we place a sample of blood into that well that contains the B antigen, that would cause agglutination in that well. However the blood in this well does not look agglutinated, suggesting this blood does not have the B antigen. And then on the right here we see a well that contains the anti-D antibodies. So if blood was placed into that well that contains the D antigen, the RH factor, that would cause agglutination. As we see the blood is agglutinated in that well, this indicates this blood most likely did have the D antigen. And therefore the blood sample that was typed on this card is A positive, meaning that it's type A blood from the ABO group and positive from the RH blood group, and we can use the ABO blood group and the RH blood group together as this sample would be A positive. If there was no agglutination in any of the wells we would say the blood type is O negative, whereas if there was agglutination in all three wells the blood type would be AB positive. In order to prevent a transfusion reaction it's essential that a blood transfusion is cross-matched with the blood type of the patient receiving the transfusion. This table will allow us to go through all the possible combinations in the ABO and RH blood groups. On the top in red we can see the different possible blood donor types. We could have O negative blood, meaning there are no antigens from the ABO or RH blood groups. A negative blood would have just the A antigen, B negative has just the B antigen, AB negative has both the A and the B antigens, but does not have the D antigen, O positive has just the D antigen, A positive has the A and the D antigens, B positive has the B and the D antigens, and AB positive has all three antigens. If we give a patient a transfusion of donor blood that is the same type that will always be safe. So we can go through diagonally here filling in for the corresponding same blood type. Now it's also going to always be safe to give a transfusion of O negative blood, because O negative blood doesn't contain any of these antigens. So ideally we could give transfusions with O negative blood to everyone, and we wouldn't have to worry about cross matching. However, there's a limiting supply of O negative blood, and we must prioritize O negative blood for patients that are O negative, because a patient that is O negative can only receive a transfusion of O negative blood. Any of the other blood types could cause a transfusion reaction. A patient with A negative blood could receive O negative or A negative blood safely. A patient with B negative blood could receive O negative or B negative blood safely. A patient with AB negative blood could receive O negative, A negative, B negative, or A B negative blood safely. However, there would be a risk of a transfusion reaction if they received blood that contained the D antigen. A patient with O positive blood could safely receive O negative or O positive, however if they were to receive a transfusion with the A or B antigens, that would cause a transfusion reaction. A patient with A positive blood can receive O negative blood, A negative blood, O positive blood, and A positive blood safely. However, they would have a transfusion reaction if they were given B negative, AB negative, AB positive, or AB positive. A patient with B positive blood could safely receive a transfusion of O negative blood or B negative blood, O positive blood, or B positive blood, however if they were to receive the A antigen, that would cause a transfusion reaction. A patient with AB positive blood could receive any of these blood types safely. The AB positive blood type is what we call the universal recipient, in contrast to the O negative blood type, which is the universal donor. Here I filled in all of the combinations that would create a transfusion reaction and should be avoided, and so the red axis show us all of the incompatible blood types and the green check marks show us all of the safe combinations for transfusion.