Blood Groups and Blood Transfusion

Question 1

What is an antigen?

Answer 1

An antigen is a substance that can stimulate an immune response and trigger the production of antibodies.

Question 2

What are antibodies?

Answer 2

Antibodies are proteins produced by the body in response to the introduction of a foreign antigen.

Question 3

Are antigen-antibody reactions specific?

Answer 3

Yes, antigen-antibody reactions are specific. A given antibody will only react with its corresponding antigen.

Question 4

What are blood groups?

Answer 4

Blood groups are systems of antigens that are controlled by specific genes. The ABO blood group system is one example.

Question 5

What does it mean to agglutinate?

Answer 5

Agglutinate means to clump together.

Question 6

What are agglutinins?

Answer 6

Agglutinins are substances that cause clumping, such as IgM antibodies.

Question 7

What are monoclonal antibodies?

Answer 7

Monoclonal antibodies are laboratory-produced and cloned molecules that bind specifically to one epitope of an antigen.

Question 8

Can you produce antibodies to antigens that you have?

Answer 8

No, you do not produce antibodies to antigens that you have. Your immune system only produces antibodies to antigens that you do not possess.

Question 9

Can you produce antibodies to antigens that you do not have?

Answer 9

Yes, you can produce antibodies to antigens that you do not have. When introduced to foreign antigens, your immune system generates specific antibodies in response.

Question 10

What are blood group antigens?

Answer 10

Blood group antigens are molecules that are present on the surface of red blood cells, and sometimes platelets and other body tissues. They are inherited characteristics.

Question 11

How are blood group antigens encoded?

Answer 11

Blood group genes, via mRNA, either directly code for red cell membrane proteins or code for enzymes that cause the production of specific red cell membrane carbohydrate sugars.

Question 12

Why are blood group systems important?

Answer 12

Blood group systems are important because we can produce antibodies to antigens that we do not have when exposed to such antigens. This can occur after a blood transfusion or during pregnancy when fetal red blood cells expressing antigens the mother doesn’t have cross into her circulation.

Question 13

What can happen when exposed to antigens you lack?

Answer 13

When exposed to antigens you lack, it can lead to sensitizing events that can cause immediate catastrophic intravascular hemolysis via complement activation (in the case of ABO incompatibility), delayed hemolytic transfusion reactions, hemolytic disease of the fetus and newborn (HDFN), and problems in selecting blood for regularly transfused patients.

Question 14

What are the consequences of blood group (allo) antibodies?

Answer 14

Blood group (allo) antibodies can cause immediate catastrophic intravascular hemolysis, delayed hemolytic transfusion reactions, hemolytic disease of the fetus and newborn (HDFN), and difficulties in selecting compatible blood for regularly transfused patients.

Question 15

What is the ABO system?

Answer 15

The ABO system is the most important blood group system in relation to transfusion. It consists of four main groups: A, B, AB, and O, with variations in population frequency.

Question 16

Where are ABO antigens expressed?

Answer 16

ABO antigens are not only present on red blood cells but also expressed on most endothelial and epithelial membranes. This has implications for ABO-incompatible solid organ and bone marrow transplantation.

Question 17

What is the structure of the terminal sugars in the ABO blood antigens?

Answer 17

The terminal sugars in the ABO blood antigens are determined by red blood cell glycoproteins or glycolipids. They have a terminal sugar called fucose (H substance). Additionally, one of two enzymes can add either galactose or N-acetylgalactosamine to the antigen, resulting in the B antigen or A antigen, respectively.

Question 18

How many main groups are there in the ABO system?

Answer 18

The ABO system consists of four main groups: A, B, AB, and O. The frequency of these groups varies among different racial populations.

Question 19

What are the implications of the ABO system in solid organ and bone marrow transplantation?

Answer 19

The ABO system has implications for ABO-incompatible solid organ and bone marrow transplantation, as compatibility between the donor and recipient’s ABO blood types needs to be considered.

Question 20

Which blood group is considered the universal donor?

Answer 20

Blood group O is considered the universal donor as it lacks A or B antigens on the red blood cells.

Question 21

Which blood group is considered the universal recipient?

Answer 21

Blood group AB is considered the universal recipient as it can receive blood from any ABO blood type without causing a transfusion reaction.

Question 22

What is the genotype and phenotype of blood group O?

Answer 22

The genotype for blood group O is OO, and the phenotype is O. It has no A or B antigens on the red blood cells and produces both anti-A and anti-B antibodies.

Question 23

What is the genotype and phenotype of blood group A?

Answer 23

The genotype for blood group A can be either AA or AO, and the phenotype is A. It has A antigens on the red blood cells and produces anti-B antibodies.

Question 24

What is the genotype and phenotype of blood group B?

Answer 24

The genotype for blood group B can be either BB or BO, and the phenotype is B. It has B antigens on the red blood cells and produces anti-A antibodies.

Question 25

What is the genotype and phenotype of blood group AB?

Answer 25

The genotype for blood group AB is AB, and the phenotype is AB. It has both A and B antigens on the red blood cells and does not produce anti-A or anti-B antibodies.

Question 26

How do we establish the blood group based on the antigen (forward grouping)?

Answer 26

To establish the blood group, we use a sample of the patient’s red blood cells (RBCs) and react them against test monoclonal anti-A and anti-B grouping antisera. The antibodies cause agglutination (clumping) of the RBCs when they react with their corresponding antigens.

Question 27

Who is considered the universal donor for RBCs?

Answer 27

Blood group O- is considered the universal donor for RBCs as it does not have A or B antigens to react with antibodies in the patient’s blood.

Question 28

Who is considered the universal recipient for RBCs?

Answer 28

Blood group AB+ is considered the universal recipient for RBCs as it does not have antibodies in the patient’s blood to react with ABO antigens, so it can receive blood from any blood group.

Question 29

Why do we develop ABO antibodies?

Answer 29

In the absence of corresponding antigens, ABO antibodies develop during the first few months after birth. For example, a blood group A individual will start to produce anti-B antibodies. This is likely due to exposure to ABH antigen-like substances from the diet or environment.

Question 30

How do we establish the blood group based on the antibody in the serum (reverse grouping)?

Answer 30

Reverse grouping involves detecting the antibodies present in a patient’s serum to confirm the blood phenotype. It is a “double-checking” mechanism that is essentially the opposite of forward grouping.

Question 31

What are the potential complications of acute hemolytic transfusion reactions due to ABO incompatibility?

Answer 31

Acute hemolytic transfusion reactions due to ABO incompatibility can result in red blood cell destruction, leading to intravascular hemolysis. In extreme cases, it can cause cardiovascular collapse, shock, renal failure, and disseminated intravascular coagulation (DIC).

Question 32

What is the incidence of ABO incompatibility in red cell units transfused?

Answer 32

Approximately 1 in 180,000 red cell units transfused may have ABO incompatibility, resulting in major morbidity in 30% of cases and contributing to patient death in 5-10% of episodes.

Question 33

What are the Rh antigens?

Answer 33

Rh antigens are components of red blood cell transmembrane proteins. The RhD and RhCE genes are responsible for encoding the antigens. The RhD gene encodes the D antigen, while the RhCE gene encodes the c, C, e, or E antigens, resulting in eight possible gene or haplotype combinations.

Question 34

How is the presence of the D antigen checked?

Answer 34

The presence of the D antigen is determined by whether an individual is RhD positive (RhD+) or RhD negative (RhD-). The D antigen is a dominant trait, with approximately 85% of the European population being RhD positive.

Question 35

What is the immunogenicity of the D antigen?

Answer 35

The D antigen is highly immunogenic, meaning it is very effective at stimulating the production of anti-D antibodies in individuals who are RhD negative and exposed to the D antigen through transfusion or pregnancy. It is the most clinically significant of the Rh antigens.

Question 36

What type of antibodies are produced against the D antigen?

Answer 36

Antibodies produced against the D antigen are predominantly IgG antibodies.

Question 37

Is there variation in the expression of the D antigen in different ethnicities?

Answer 37

Yes, there is variation in the expression of the D antigen in different ethnicities. For example, individuals of Japanese and black African descent may have an intact gene for the D antigen that is either not expressed or expressed at very low levels.

Question 38

What is sensitization in relation to the Rh antigen?

Answer 38

Sensitization refers to the stimulation of the production of anti-D antibody after exposure to the D antigen. This can occur when an Rh-negative individual is exposed to Rh-positive blood, such as during pregnancy or blood transfusion.

Question 39

What is the impact of Rh sensitization?

Answer 39

Rh sensitization can lead to hemolytic disease of the fetus and newborn (HDFN) when an Rh-negative mother becomes sensitized to the Rh antigen and produces anti-D antibodies that can cross the placenta and attack Rh-positive red blood cells in the fetus.

Question 40

How can Rh sensitization be prevented?

Answer 40

Rh sensitization can be prevented by administering Routine Antenatal Anti-D Prophylaxis (RAADP) to Rh-negative, non-sensitized women. This involves the administration of anti-D immunoglobulin to destroy any Rh-positive fetal red blood cells in the maternal circulation.

Question 41

What are some sensitizing events that may require additional doses of anti-D immunoglobulin?

Answer 41

Sensitizing events that may require additional doses of anti-D immunoglobulin include delivery, miscarriage, chorionic villus sampling (CVS), amniocentesis, falls, trauma, and antepartum hemorrhage (APH).

Question 42

What are the practical aspects of compatibility testing before transfusion?

Answer 42

The minimum requirements for compatibility testing include ABO compatibility, Rh D compatibility (Rh D-negative for Rh D-negative patients), and Kell compatibility (Kell negative for Kell-negative patients). For patients with clinically significant antibodies, units that are negative for the specific antigen to which the patient has developed antibodies should be selected.

Question 43

What tests are used to estimate the volume of fetal cells in maternal circulation?

Answer 43

The Kleihauer test is used to estimate the volume of fetal cells in maternal circulation. It involves staining the cells and identifying fetal red blood cells (pink) and maternal red blood cells (pale). Flow cytometry can also be used to confirm the volume and administer further anti-D if needed.

Question 44

What components of blood can be transfused?

Answer 44

Blood component therapy is commonly used instead of whole blood transfusion. The components that can be transfused include red blood cells (RBCs), fresh frozen plasma (FFP), platelets, cryoprecipitate, and buffy coats. Plasma derivatives such as human albumin solution (HAS), clotting factor concentrates, and immunoglobulin solutions are also used.

Question 45

How is donor selection and infection transmission minimized in transfusion?

Answer 45

Donor eligibility is assessed through a questionnaire covering health, lifestyle, travel, medical history, and medications. Precautions are taken to reduce the transmission of prion-associated diseases. Routine screening for infections includes Hepatitis B, HIV 1+2, Hepatitis C, HTLV I+II, and Syphilis. Special circumstances such as Malarial antibodies, West Nile virus antibodies, and Trypanosoma cruzi antibodies are also considered.

Question 46

What is the process of blood donation and collection?

Answer 46

Suitable donors attend donation centers where whole or part blood donations are taken. Blood is collected into bags containing a preservative and anticoagulant called CPD (citrate phosphate dextrose). The donations are filtered to remove white blood cells (pre-storage leukodepletion). Further manufacturing is done to separate blood into components such as RBCs, plasma, and platelets. Plateletpheresis or apheresis involves directly collecting the required product from the patient using a special machine.

Question 47

What are some special requirements for transfusion?

Answer 47

Special requirements for transfusion include irradiated blood, washed red cells/platelets, single donor platelets, HLA/HPA selected products, and pathogen-inactivated FFP (fresh frozen plasma).

Question 48

How does the transfusion process work?

Answer 48

The need for transfusion is identified based on specific indications such as acute bleeding, bone marrow failure, or thalassemia. When there are no alternatives, blood is prescribed, and the appropriate unit(s) of blood are found by the laboratory. The blood is transported to the clinical area, where a nurse verifies the patient and the product. The transfusion begins with monitoring, and for specific requirements like CMV-negative blood, the nurse ensures that the blood meets those requirements.