Circulatory system: Blood grouping and Rhesus factor-2

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.

Antibodies against the Rh group are not typically seen in the blood, in contrast to the ABO group. Only Rh people who have been exposed to Rh+ blood can develop them. An Rh individual who receives a transfusion of Rh+ blood develops anti-Rh antibodies in response to the foreign antigen. 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.

An associated condition can occasionally happen when a Rh-woman is carrying a Rh+ fetus. 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 rupture exposes the mother to Rh fetal blood during labor or in the event of a miscarriage. After that, she starts to make anti-Rh antibodies. Her anti-Rh antibodies may cross the placenta and agglutinate the fetal RBCs if she conceives once more and the fetus is Rh+. Agglutinated RBCs hemolyze, and the infant is born with hemolytic disease of the newborn (HDN) or erythroblastosis fetalis, a severe form of anemia.

HDN is simpler to avoid than to cure. A Rh-woman who becomes pregnant with (or experiences a miscarriage or abortion with) a Rh child may receive an injection of anti-Rh antibodies known as Rh immune globulin. Fetal RBC agglutinogens cannot cause her immune system to produce anti-Rh antibodies because the immune globulin binds them.

The ABO Blood Group

Blood Typing

To prevent blood type mismatches, the potential donor's blood is typed. A single drop of blood is combined with various solutions containing the antibodies known as antisera as part of the ABO blood typing technique. Agglutination will take place between the agglutinin and the corresponding agglutinogen when serum containing anti-A or anti-B agglutinins is added to a blood sample. RBCs that have anti-A antibodies agglutinate when exposed to A antigen. If B antigens are present and RBCS agglutinate with serum containing anti-B antibodies. The blood type is AB if both drops agglutinate, and type 0 if neither drop does so.

Cross matching is also done because blood group compatibility is crucial. Agglutination of donor RBCs by recipient serum and recipient RBCs by donor serum are tested for during cross-matching. The Rh factors are categorized in the same way as ABO blood types.