Faculty of Allied Faculty of Allied Medical ScienceMedical Science

Blood BankingBlood Banking(MLBB-201)(MLBB-201)

Fall 2013Fall 2013

Blood Cell (Group) Blood Cell (Group) AntigensAntigens

Prof. Dr. Nadia Aly SadekProf. Dr. Nadia Aly Sadek

Professor in HematologyProfessor in Hematology

Blood Bank Director, MRIBlood Bank Director, MRI

University of AlexandriaUniversity of Alexandria

OutcomesOutcomes

By the end of the lecture, the students By the end of the lecture, the students willwill::

- -Globally recognize the blood group Globally recognize the blood group antigensantigens

- -Know the clinical importance of blood Know the clinical importance of blood group antigensgroup antigens

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

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

The ABO system is coded on The ABO system is coded on chromosome 9, the Rh system on chromosome 9, the Rh system on chromosome 1chromosome 1..

Most red cell genes are expressed as Most red cell genes are expressed as codominant antigens = both genes codominant antigens = both genes are expressed in the heterozygote are expressed in the heterozygote state i.e AA, AOstate i.e AA, AO..

Red cell antigens are determined either Red cell antigens are determined either by:by:

- carbohydrate structure or- carbohydrate structure or - protein structure- protein structure

Carbohydrate antigensCarbohydrate antigens

These are indirect gene products e.g. These are indirect gene products e.g. ABO, Lewis, P. ABO, Lewis, P.

The gene codes for an intermediate The gene codes for an intermediate product, usually an enzyme that product, usually an enzyme that makes the antigenic specificity by makes the antigenic specificity by transferring sugar molecules onto transferring sugar molecules onto protein or lipid.protein or lipid.

Protein-defined antigensProtein-defined antigens

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

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

This is best applied in transplantation.This is best applied in transplantation.

Clinical importanceClinical importance

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

This depends on:-This depends on:- - Frequency of the antigens and - Frequency of the antigens and

alloantibodiesalloantibodies - Characteristics of the - Characteristics of the

alloantibodies.alloantibodies.

Characteristics of Characteristics of AlloantibodiesAlloantibodies

- - Thermal rangeThermal range - Immunoglobulin class (IgG, IgM).- Immunoglobulin class (IgG, IgM). - Ability to fix complement- Ability to fix complement

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

Anti-DAnti-D

The Rh antigen is the most The Rh antigen is the most immunogenic red cell antigen after A immunogenic red cell antigen after A and B.and B.

It can stimulate the production of It can stimulate the production of anti-D only after blood transfusion or anti-D only after blood transfusion or pregnancy in the majority of Rh-pregnancy in the majority of Rh-negative individuals.negative individuals.

InheritanceInheritance

Inheritance of ABH antigens is Inheritance of ABH antigens is usually associated with usually associated with predisposition to certain diseases.predisposition to certain diseases.

- Group A individuals have 1.2 times - Group A individuals have 1.2 times the risk to develop cancer stomach the risk to develop cancer stomach than group O or B. They have than group O or B. They have hypoacidity, they should receive hypoacidity, they should receive citrus fruits and Vit B12.citrus fruits and Vit B12.

- Group O individuals have 1.4 times - Group O individuals have 1.4 times more risk to develop peptic ulcer than more risk to develop peptic ulcer than the other groups.the other groups.

- Non-secretors of ABH have 1.5 times - Non-secretors of ABH have 1.5 times the risk to develop peptic ulcers than the risk to develop peptic ulcers than secretors.secretors.

- ABH antigens are more weakly - ABH antigens are more weakly expressed on RBCs of leukemic expressed on RBCs of leukemic persons.persons.

Blood Groups and Blood Groups and CoagulationCoagulation

- Group O healthy individuals have - Group O healthy individuals have levels of von Willebrand factor (vWF) levels of von Willebrand factor (vWF) and factor VIII 25% lower than the and factor VIII 25% lower than the other groups.other groups.

- The H antigen (the highest in group - The H antigen (the highest in group O) causes accelerated clearance of O) causes accelerated clearance of vWF. They are less likely to have vWF. They are less likely to have venous thrombosis.venous thrombosis.

Study QuestionsStudy Questions

Complete:-Complete:- Red cell antigens are determined by:-Red cell antigens are determined by:- 1. 1. ……………………..structure..structure 2. 2. ……………………..structure..structure State right or false:State right or false: A- All red cell antigens are erythroid A- All red cell antigens are erythroid

specific ( ) specific ( ) B- Anti-D antibodies are naturally B- Anti-D antibodies are naturally

occurring ( )occurring ( )

AssignmentsAssignments

Each Student will be selected for an Each Student will be selected for an assignmentassignment::

Universal blood groupUniversal blood group

Recommended TextbooksRecommended Textbooks

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