Faculty of Allied Medical Science Blood Banking (MLBB-201) Fall 2013 Fall 2013

Blood Cell (Group) Antigens Prof. Dr. Nadia Aly Sadek Professor in Hematology Blood Bank Director, MRI University of Alexandria

Outcomes By the end of the lecture, the students will: - Globally recognize the blood group antigens - Know the clinical importance of blood group antigens

Twenty-five blood group systems have been recognized. Each system is a series of red cell antigens, determined by a single genetic locus or very closely linked loci. Twenty-five blood group systems have been recognized. Each system is a series of red cell antigens, determined by a single genetic locus or very closely linked loci.

Most of the antigens (apart from those of the ABO system) were detected by antibodies stimulated by transfusion or pregnancy. Most of the antigens (apart from those of the ABO system) were detected by antibodies stimulated by transfusion or pregnancy.

The ABO system is coded on chromosome 9, the Rh system on chromosome 1. Most red cell genes are expressed as codominant antigens = both genes are expressed in the heterozygote state i.e AA, AO.

Red cell antigens are determined either by: Red cell antigens are determined either by: - carbohydrate structure or - carbohydrate structure or - protein structure - protein structure

Carbohydrate antigens These are indirect gene products e.g. ABO, Lewis, P. These are indirect gene products e.g. ABO, Lewis, P. The gene codes for an intermediate product, usually an enzyme that makes the antigenic specificity by transferring sugar molecules onto protein or lipid. The gene codes for an intermediate product, usually an enzyme that makes the antigenic specificity by transferring sugar molecules onto protein or lipid.

Protein-defined antigens These are direct gene products, and the specificity is determined by the inherited amino acid sequence and the conformation of the protein. These are direct gene products, and the specificity is determined by the inherited amino acid sequence and the conformation of the protein.

A few red cell antigens are erfythroid specific ( Rh, LW, Kell, MNs ). The others are also expressed in many other tissues. A few red cell antigens are erfythroid specific ( Rh, LW, Kell, MNs ). The others are also expressed in many other tissues. This is best applied in transplantation. This is best applied in transplantation.

Clinical importance The main clinical importance of a blood group system depends on the capacity of the alloantibody directed against the antigens,( not possessed by the individual), to cause destruction of transfused red cells or to cross the placenta and give rise to hemolytic disease in the fetus or newborn. The main clinical importance of a blood group system depends on the capacity of the alloantibody directed against the antigens,( not possessed by the individual), to cause destruction of transfused red cells or to cross the placenta and give rise to hemolytic disease in the fetus or newborn.

This depends on:- This depends on:- - Frequency of the antigens and alloantibodies - Frequency of the antigens and alloantibodies - Characteristics of the alloantibodies. - Characteristics of the alloantibodies.

Characteristics of Alloantibodies - Thermal range - Thermal range - Immunoglobulin class (IgG, IgM). - Immunoglobulin class (IgG, IgM). - Ability to fix complement - Ability to fix complement

Anti-A and Anti-B are naturally occurring antibodies and can cause severe intravascular hemolysis after an incompatible blood transfusion. Anti-A and Anti-B are naturally occurring antibodies and can cause severe intravascular hemolysis after an incompatible blood transfusion.

Anti-D The Rh antigen is the most immunogenic red cell antigen after A and B. The Rh antigen is the most immunogenic red cell antigen after A and B. It can stimulate the production of anti-D only after blood transfusion or pregnancy in the majority of Rh-negative individuals. It can stimulate the production of anti-D only after blood transfusion or pregnancy in the majority of Rh-negative individuals.

Inheritance Inheritance of ABH antigens is usually associated with predisposition to certain diseases. Inheritance of ABH antigens is usually associated with predisposition to certain diseases. - Group A individuals have 1.2 times the risk to develop cancer stomach than group O or B. They have hypoacidity, they should receive citrus fruits and Vit B12. - Group A individuals have 1.2 times the risk to develop cancer stomach than group O or B. They have hypoacidity, they should receive citrus fruits and Vit B12.

- Group O individuals have 1.4 times more risk to develop peptic ulcer than the other groups. - Group O individuals have 1.4 times more risk to develop peptic ulcer than the other groups. - Non-secretors of ABH have 1.5 times the risk to develop peptic ulcers than secretors. - Non-secretors of ABH have 1.5 times the risk to develop peptic ulcers than secretors. - ABH antigens are more weakly expressed on RBCs of leukemic persons. - ABH antigens are more weakly expressed on RBCs of leukemic persons.

Blood Groups and Coagulation - Group O healthy individuals have levels of von Willebrand factor (vWF) and factor VIII 25% lower than the other groups. - The H antigen (the highest in group O) causes accelerated clearance of vWF. They are less likely to have venous thrombosis. - The H antigen (the highest in group O) causes accelerated clearance of vWF. They are less likely to have venous thrombosis.

Study Questions Complete:- Red cell antigens are determined by:- Red cell antigens are determined by:- 1. …………..structure 1. …………..structure 2. …………..structure 2. …………..structure State right or false: State right or false: A- All red cell antigens are erythroid specific ( ) A- All red cell antigens are erythroid specific ( ) B- Anti-D antibodies are naturally occurring ( ) B- Anti-D antibodies are naturally occurring ( )

Assignments Each Student will be selected for an assignment: Universal blood group

Recommended Textbooks Sally V. Rudmann. Textbook of Blood Banking and Transfusion Medicine Sally V. Rudmann. Textbook of Blood Banking and Transfusion Medicine. 2008