RH blood group system

medical

1. Rh Blood Group System Hammad Tariq BSML-FA20-001 Aoun Raza BSML-FA20-00 3 Ashraf Ali BSML-FA20-011 Umar Mustafa BSML-FA20-013

2. Contents : Introduction Historical development of the Rh- Hr system Mendelian inheritance of Rh- Hr system Punnett square of Rh-blood group Rhesus factor incompatibility

3. Introduction: The Rh blood group system is one of the most polymorphic and antigenic blood group systems. It is second only to ABO in importance in blood transfusion and is well known as a primary cause of hemolytic disease of the fetus and newborn (HDFN). The principal antigen is D, and the terms Rh positive and Rh negative refer to the absence of D antigen.

4. Historical development of the Rh- Hr system: In 1939, Philip Levine and Rufus Stetson   described a hemolytic transfusion reaction in an obstetric patient following delivery of stillborn infant. The women required transfusion. Her husband, who had the same ABO type, was selected as her donor, after transfusion the recipient, demonstrated the classic symptoms of acute hemolytic transfusion reaction.

5. Subsequently an antibody was isolated from the mother’s serum that react both at 37°C and 20 °C with the father’s red cells. It was postulated that the fetus and the father possessed a common factor that the mother lacked. While the mother carry the fetus, the mother was exposed to this factor and subsequently, subsequently built up an antibody that reacted against the transfused red cells from the father and resulted in hemolytic transfusion reaction.

6. Landsteiner and Wiener reported on an antibody by guinea pigs and rabbits when these animals were transfused with rhesus monkey red cells. This antibody which agglutinated 85% of human red cells was named Rh. The name Rh was retained for the human produced antibody. Anti-rhesus formed by the animals was renamed anti-LW (Landsteiner and Wiener).

7. Mendelian Inheritance of Rh blood group: The Rh blood group system is inherited in a Mendelian manner (involves a dominant and recessive pattern). There are two main alleles for the Rh factor: Rh-positive (D or +) and Rh-negative (d or -). The inheritance follows an autosomal dominant pattern. This means that if a person inherits at least one Rh-positive allele from either parent, they will express the Rh-positive blood type. For a person to be Rh-negative, they must inherit two recessive Rh alleles.

8. Rh factors are genetically determined. The Rh-positive gene is dominant (stronger) and even when paired with an Rh-negative gene, the positive gene takes over. If a person has the genes + +, the Rh factor in the blood will be positive. If a person has the genes + -, the Rh factor will also be positive. If a person has the genes - -, the Rh factor will be negative.

9. Rh status is inherited from our parents, separately from our blood type. If you inherit the dominant Rhesus D antigen from one or both of your parents, then you are Rh-positive. If you do not inherit the Rhesus D antigen from either parent, then you are Rh-negative. So, it is possible for two people who are Rh-positive to produce a child that’s Rh- negati ve, but only if neither parent passes along Rhesus D.

10. Punnett square of Rh-blood group: The simple Punnett square here demonstrates how this is possible.

11. A baby receives one gene from the father and one from the mother. More specifically, consider the following: If a father's Rh factor genes are + +, and the mother's are + +, the baby will have one + from the father and one + gene from the mother. The baby will be: + + Rh positive

12. If a father's Rh factor genes are + +, and the mother's are - -, the baby will have one + from the father and one - gene from the mother. The baby will be: + - Rh positive

13. If the father's genes are + - Rh positive, and the mother's are + - Rh positive, the baby can be: + + Rh positive + - Rh positive - - Rh negative

14. If the father's genes are - -, and the mother's genes are + -, the baby can be: + - Rh positive - - Rh negative

15. If the father's genes are - -, and the mother's genes are also - -, then baby will be: - - Rh negative

16. Rhesus factor incompatibility: A medical problem can occur when a woman, who is Rh-, is pregnant with a Rh+ fetus. The first child may have no difficulty, but subsequent similar pregnancies may produce severely anemic newborns. Exposure to the red blood cells of the first Rh+ fetus appears to protect the Rh- mother, thus potentially preventing her from developing antibodies that can cause brain damage in any subsequent Rh+ fetus. Damage to the fetal brain can occur as a result of the severe destruction of red blood cells.

17. There are preventable measures available to prevent the severe effects of Rh incompatibility by transfusions to the fetus. Mother can receive Rh immunoglobulin ( RhoGAM ) immediately after her first and any subsequent pregnancies involving a Rh+ fetus. This immunoglobulin effectively destroys the fetal red blood cells before the mother’s immune system is stimulated. Therefore, the mother avoids becoming actively immunized against the Rh antigen and will not produce antibodies that could attack the red blood cells of a future Rh+ fetus.

18. References : Hematology: Basic Principles and Practices https://www.bloodgroupgenomics.org/blog-blood-experts/articles/history-rh-blood-group-how-genomics-changing-rhd-typing/ https://stanfordbloodcenter.org/can-two-rh-positive-parents-have-an-rh-negative-child/