Circulatory system: Blood grouping and Rhesus factor

Blood Groups

On the surface of every red blood cell is an inherited mixture of glycoprotein and glycolipid antigens. These molecules called antigens, which can initiate an immune response, allow the immune system to distinguish between our own cells and foreign invaders. Karl Landsteiner, a scientist, made the initial discovery of the blood group in 1901.

RBC antigens are known as agglutinogens in blood typing because they produce RBC agglutination (clumping of RBCs) in incompatible transfusions. Agglutinins are the name for the plasma antibodies that respond against them. Blood is divided into numerous blood types based on the presence or absence of certain antigens. More than 100 antigens and at least 24 blood types can be found on the surface of RBCs. The blood types include the ABO, Rh, Kell, Lewis, and Duffy systems. This article only covers the ABO and Rh blood groupings.

The ABO Blood Group

Is decided by those who only possess those who possess both A and B.

The ABO blood group is made up of blood types A, B, and o. The presence or absence of agglutinogens A and B on the RBCs determines the ABO blood type in genetic terms. Antigen A carriers have type A blood. Type B people only have antigens B; type AB people have both antigens A; and type 0 people have neither antigens A nor B.

2 to 8 months after birth, the plasma starts to show the ABO group agglutinins (antibodies). Between the ages of 8 and 10, they are at their highest concentrations, and they continue to decline for the rest of a person's life.

Except for those on one's own RBCs, AB apglutinins (antibodies) respond against all AB agglutinogens (antigen). Anti-A antibody, or agglutinin that responds against antigen A, is present in people with type o or type B blood, or in anyone who does not have agglutinogen A. Anti-B antibodies, which are present in type O and type A people—those who lack agglutinogen B—are agglutinins that react against antigen B.

When entire blood or blood components are infused into blood vessels during an incompatible blood transfusion, the recipient's plasma's agglutinin binds to several RBCs at once, causing them to aggregate and become agglutinated. RBCs hemolyze during an antigen-antibody response known as a transfusion reaction, releasing their hemoglobin into the blood plasma. Free hemoglobin can obstruct kidney tubules and result in acute renal failure, which can be fatal. Because of this, type B or AB blood should never be transfused into a person with type A (anti-B) blood. Never give type A or AB blood to someone who has type B (anti A). Blood of types A, B, or AB cannot be safely given to type O (anti-A and anti-B) people.

Because type AB lacks both anti-A and anti-B agglutinins and won't agglutinate donor RBCs of any ABO type, it was once referred to as the universal receiver. Similar to type 0, type O blood has neither A nor B antigens on its RBCs, thus it can theoretically donate blood to all four ABO blood types. This is why type O blood was originally referred to as the universal donor. The other agglutinogens in blood that can cause transfusion reactions are not considered in these classifications, which makes them dangerous and misleading.

The Rh Blood Group

Rh antigen was first discovered in rhesus monkeys in 1940, therefore giving rise to the moniker Rh blood grouping system. Three genes, C, D, and E, which may code for the Rh antigen, control this group. The D protein is the part of these three genes that is most immunogenic. Rh+ (Rh positive) refers to individuals whose RBCs contain Rh antigens, while Rh- (Rh negative) refers to individuals without Rh antigens.

Anti-Rh persons are not typically found in the blood, unlike the ABO group. Only Rh-ve people exposed to Rh+ve blood develop them. An Rh-ve person who gets a Rh+ve blood transfusion experiences the production of anti-Rh antibodies by the recipient's immune system. This type of transfusion does not result in hemolysis since the body needs time to react and begin producing antibodies. However, if Rh+ blood is transfused a second time, it can result in a severe transfusion reaction where the recipient's antibodies attack and rupture the donor RBCs.

When a Rh+ve fetus is carried by a Rh-ve woman, a similar disease might occasionally happen. Due to the placenta's usual ability to prevent the mixing of maternal and fetal blood, the first pregnancy is most likely to go smoothly. However, placental ripping during labor or in the event of a loss exposes the mother to Rh+ve blood. After that, she starts to make anti-Rh antibodies. Her anti-Rh antibodies may pass through the placenta and agglutinate fetal RBCs if she gets pregnant again with a Rh+ve fetus. The baby is born with a severe anemia known as hemolytic disease of the newborn (HDN) or erythroblastosis fetalis when agglutinated RBCs hemolyze.

HDN is simpler to avoid than to cure. A Rh- woman who gives birth (or experiences a miscarriage or abortion) can receive an injection of Rh immune globulin, which contains anti-Rh antibodies (Rho GAM) Fetal RBC agglutinogens cannot cause her immune system to develop anti-Rh antibodies because the immune globulin binds them.

Blood Typing

To prevent blood type mismatches, the potential donor's blood is typed. A single drop of blood is combined with several solutions containing the antibodies known as antisera during the ABO blood typing process. Agglutination will take place between the agglutinin and the appropriate agglutinogen when serum containing anti-A or anti-B agglutinins is introduced to a blood sample (A or B). RBCs that are agglutinated with anti-A antibodies have the A antigen. If RBCs that have B antigens agglutinate serum that has anti-B antibodies. The blood type is AB if both drops agglutinate; if neither drop does, the blood type is O.

2 to 8 months after birth, the plasma starts to show the ABO group agglutinins (antibodies). Between the ages of 8 and 10, they reach their peak concentrations, after which they gradually decrease for the rest of a person's life.

Except for those on one's own RBCs, AB agglutinins (antibodies) respond against all AB agglutinogens (antigen). Antigen A-specific agglutinin, or anti-A antibody, is found in the plasma of people with type O or type B blood, or anyone who does not have agglutinogen A. It reacts with antigen A. Anti-B antibodies, which are present in type 0 and type A people who do not have agglutinogen B, are agglutinins that react against antigen B.

When entire blood or blood components are infused into blood vessels during an incompatible blood transfusion, the recipient's plasma's agglutinin binds to several RBCs at once, causing them to aggregate and become agglutinated. RBCs hemolyze during an antigen-antibody response known as a transfusion reaction, releasing their hemoglobin into the blood plasma. Free hemoglobin can obstruct kidney tubules and result in acute renal failure, which can be fatal. Because of this, type B or AB blood should never be transfused into a person with type A (anti-B) blood. Never give type A or AB blood to someone who has type B (anti A). Blood of types A, B, or AB cannot be safely given to type O (anti-A and anti-B) people.

Because type AB lacks both anti-A and anti-B agglutinins and won't agglutinate donor RBCs of any ABO type, it was once referred to as the universal receiver. Similar to type O, type O blood has neither A nor B antigens on its RBCs, making it potentially possible to donate blood to all four ABO blood types. This is why type O was originally referred to as the universal donor. The various agglutinogens in blood that can cause transfusion responses are not considered in these classifications, which makes them unsafe and misleading.