L2- The ABO Blood Group System Student (2) PDF

Blood Group System (The ABO Blood Group System) Prepared by Prof. Dr. Manal A. Shams Eldin Eltelbany Professor of Clinical Pathology ILOs Outline the history of the discovery of the ABO blood group. List all antigens and antibodies associated with the ABO...

Blood Group System (The ABO Blood Group System) Prepared by Prof. Dr. Manal A. Shams Eldin Eltelbany Professor of Clinical Pathology ILOs Outline the history of the discovery of the ABO blood group. List all antigens and antibodies associated with the ABO and H blood group systems. Describe the development of A, B, and H antigens. Diagram the chemical structure of A, B, and H antigens. State frequency of occurrence of the ABO blood groups. Explain the relationship of the H antigen to the ABO blood group system. Outline the genetics and biochemistry of the Bombay phenotype. Outline subgroups of A Outline the characteristics A, B, and H antibodies. Explain the clinical significance of ABH antibodies. IMMUNOHEMATOLOGY Definition: Immunohematology is the study of blood group antigens and antibodies, HLA antigens and antibodies, pretransfusion testing, identification of unexpected alloantibodies, immune hemolysis, autoantibodies, drugs, blood collection, blood components, cryopreservation of blood, transfusion-transmitted viruses, tissue banking and organ transplantation, blood transfusion practice, safety, quality assessment, records, blood inventory management, and blood usage review The study of Immunohematology focuses on specific antigens and antibodies related to blood group systems. The antigens are related to the red blood cell membrane. The antigens are inherited characteristics. Each individual receives a combination of antigens from his or her parents. The antibodies are created by an immune response to the specific antigen. INTRODUCTION The major blood group systems are the primary focus of blood banking and transfusion therapy. Blood group systems and antibodies form the basis for pretransfusion testing. Antigens and antibodies are the etiologies of hemolytic disease of the fetus and newborn and hemolytic transfusion reactions. Some antigens play a primary role in transplant therapy. Pretransfusion testing focuses on ABO and Rh antigen testing, as well as screening for antibodies in the plasma. INTERNATIONAL SOCIETY OF BLOOD TRANSFUSION (ISBT) Historically, all blood group antigens have been assigned a name and an abbreviation. The International Society of Blood Transfusion (ISBT) examined this identification system, and a committee was developed in 1980 to standardize blood group terminology. This committee, the Working Party on Terminology for Red Cell Antigens, was originally established to create a terminology system suitable for computer software. This “new” system intended to standardize the original terminology. The committee’s criteria required genetic studies and serologic testing prior to an antigen’s assignment to a blood group system. The committee’s work resulted in the development of blood group systems based on genetics. The ISBT symbols and numbers are related to each system as appropriate.  ISBT Blood Group System Summary of ISBT Nomenclature Blood group systems: Groups of related RBC antigens inherited according to Mendelian genetics - RBC antigens are inherited and are composed of proteins, glycoproteins, and glycolipids. HISTORICAL PERSPECTIVE OF THE ABO BLOOD GROUP SYSTEM Karl Landsteiner discovered the ABO blood group system in 1900, which incited the beginning of modern blood banking and transfusion medicine. Landsteiner performed a series of experiments demonstrating serological incompatibilities between individuals. In 1901, using his blood and the blood of his colleagues, he mixed the serum of some individuals with other people’s cells. Inadvertently, he was the first person to perform forward and reverse grouping. This series of experiments led him to discover three of the four ABO groups: A, B, and O. The RBCs have A antigens on their surface and B antibodies in the blood plasma. The RBCs have B antigens on their surface and A antibodies in the blood plasma. The RBCs have both A and B antigens on their surface and no A or B antibodies at all in the blood plasma. The RBCs have neither A or B antigens on their surface but the blood plasma have both A and B antibodies. HISTORICAL PERSPECTIVE OF THE ABO BLOOD GROUP SYSTEM Cont Shortly after Landsteiner’s initial discovery, his associates, Alfred von Decastello and Adriano Sturli, discovered the fourth blood group, AB. In later studies, Landsteiner correlated the presence of the ABO antigens on red cells and the reciprocal agglutinating antibodies in the serum of the same individual (e.g. A antigens on red blood cells and anti-B in the serum). This discovery was labeled Landsteiner’s Law or Landsteiner’s Rule. This rule is the basis for all transfusion therapy as well as a guideline for determining the compatibility of donor and recipients. ABO grouping is one of the primary tests performed in the blood bank. Applications of ABO grouping are summarized in the next slide. Applications of ABO Grouping Pre-transfusion Testing Prenatal Testing Presurgical Testing Paternity Determination Transplant Matching Donor Testing HISTORICAL PERSPECTIVE OF THE ABO BLOOD GROUP SYSTEM Cont Felix Bernstein discovered the group inheritance pattern of multiple alleles at one locus in 1924. This discovery explained the inheritance of ABO blood groups. Additionally, it was established that an individual inherits one ABO gene from each parent. These genes produce the antigens present on the surface of an individual’s red cells. Like Landsteiner’s discoveries, Bernstein’s determination of inheritance patterns of the ABO group has played a major role in the knowledge base for all blood group systems. In 1930, O. Thompson postulated a four-allele system of inheritance. This proposed system was based on the discovery of Emil Frieherr von Dungern and Ludwig Hirtzfeld in 1911—that the group A antigen can be divided into two subgroups, A1 and A2. Thompson expanded this premise and proposed the four allelic genes: A1, A2, B, and O. His expansion of Landsteiner’s original findings enhanced the ability to provide safe blood for transfusion.  Ch 9 Ch 9 ABO genes located on A chromosome 9 (autosomal B chromosome), each gene codes for a different glycosyl transferase enzyme giving the different blood group Father Mother All individuals inherits one alleles from the mother and one from the father, both alleles show co dominant inheritance  What do co-dominant genes mean? This meant that if a person inherited one A group gene and one B group gene their red cells would possess both the A and B blood group antigens. i.e. Both genes will be express, no one dominate the other. These alleles were termed : A : Produced the A antigen. B : Produced the B antigen. O : Non functional and produced neither A nor B antigen and keep the original H antigen  Red cell antigens and blood group antibodies The clinical significance of blood groups in blood transfusion is that individuals who lack a particular blood group antigen may have preformed antibodies or may produce antibodies reacting with that antigen, which may lead to a transfusion reaction. Approximately 400 red blood cell group antigens have been described. The different blood group antigens vary greatly in their clinical significance, with the ABO and Rh (formerly Rhesus) groups being the most important. ** Clinically Important Blood Group Systems Red cell antigens and blood group antibodies Cont ABO system ---- Biochemical considerations ▪ The protein that defines the ABO antigens is a glycosyltransferase that is encoded from a single gene for which there are three major alleles, A, B and O. ▪ The A and B alleles catalyse the addition of different carbohydrate residues (N-acetyl galactosamine for group A and galactose for group B) to a basic antigenic glycoprotein or glycolipid with a terminal sugar l-fucose on the red cell, known as the H substance (see Fig. ). Structure of ABO blood group antigens. Each consists of a chain of sugars attached to lipids or proteins which are an integral part of the cell membrane. The H antigen of the O blood group has a terminal fucose (fuc). The A antigen has an additional N-acetyl galactosamine (galnac), and the B antigen has an additional galactose (gal). glu, glucose. The “A” gene codes for an enzyme (1-3 N-acetylgalactosaminyl transferase) that adds N-acetylgalactosamine to the terminal sugar of the H antigen RBC Glucose Galactose N-acetylglucosamine Galactose N-acetylgalactosamine Fucose The “B” gene codes for an enzyme“ (1-3 D-galactosyl transferase) that adds D-galactose to the terminal sugar of the H antigen RBC Glucose Galactose N-acetylglucosamine Galactose Galactose Fucose  Certain blood types possess more H antigen than others: O>A2>B>A2B>A1>A1B Greatest Least amount of H amount of H Red cell antigens and blood group antibodies ABO system Cont ▪ The O allele is non-functional and so does not modify the H substance. Although there are six common genotypes, the absence of a specific anti-H prevents the serological recognition of more than four phenotypes (see Table ). ▪ The A allele actually itself has two variants, A1 and A2 , but these are of minor clinical significance. A2 cells react more weakly than A1 cells with anti-A, and patients who are A2 B can be wrongly grouped as B. Red cell antigens and blood group antibodies ABO system Cont Distribution of A, B and H antigens ▪ The A, B and H antigens are present on most body cells, including white cells and platelets.  Alleles at a locus independent of the ABO blood group locus, known as the secretor locus, determine an individual's ability to secrete the ABH antigens in saliva and other body fluids eg plasma, semen and sweat. There are two genes, Se and se, where Se is dominant to se. In other words, an individual with at least one Se gene is a secretor. A antigen Secretor H antigen in and/or (Se Se or Se se) secretions B antigen Non secretor No antigens secreted (se se) in saliva or other body fluids ***The ABO Blood Group System in Egypt In the Egyptian population: O records the highest value, followed by B and A. O>B>A The homozygous types were as follows: OO 31.94%: AA, 6.43%; and BB, 3.28%. The heterozygous types were AO, 28.67%; BO, 20.47%; and AB, 9.78%. The ABO Blood Group System in UK  The A allele actually itself has two variants, A1 and A2 , but these are of minor clinical significance. The difference between A1 and A2 subgroups is partly quantitative, the A1 cells have more A antigens sites than A2 i.e. A2 is a weak form of A antigen Differentiation between A1 and A2 is made by anti-A and anti-A1 Group A red cells that react with both anti-A and anti- A1 are classified as A1. The red cells that react with anti-A only and not with anti- A1 are classified as A2. A2 The surface of A2 cells have fewer A antigen sites than A1 cells  A2 considered as a weaker form of A antigen A2 cells react more weakly than A1 cells with anti-A, and patients who are A2 B can be wrongly grouped as B. The plasma of group A2 and A2B individuals may contain anti-A1 A3,Ax,Aend,Am and Ael (rare ABO genes) B3, Bx, Bm and Bel (rare ABO genes)  Bombay Phenotype (Oh) Inheritance of hh, which is very rare. The h gene results in little or no production of the enzyme L-fucosyl transferase so NO H antigen to be produced The patient RBCs have no H, A, or B antigen (patient types as O) Bombay RBCs are NOT agglutinated with anti-A, anti-B, or anti-H (no antigens present) Bombay serum has strong anti-A, anti-B and anti-H, agglutinating ALL ABO blood groups  What blood ABO blood group would you use to transfuse this patient with Bombay Phenotype ?  Bombay Phenotype (Oh) Cont What blood ABO blood group would you use to transfuse this patient? Another Bombay Group O RBCs cannot be given because they still have the H antigen You have to transfuse the patient with blood that contains NO H antigen  The cord blood cells have fewer A,B or H antigens. After birth, the expression of A,B and H antigens increase until the age of 3 years. Thereafter, in health remain stable throughout life.  Arise in response to ABH antigens-like substances present on bacterial, viral or animal molecules. Start to appear at the age of 3 to 6 months. Titers of ABO antibodies vary with age, reaching a peak in adult life and then decline in old age. Naturally occurring Anti-A and Anti-B are antibodies that react better at cold temperature (4oC) and potentially react at 37 oC (wide thermal range).  Always have some IgM component and, in group A and B persons, they are almost entirely IgM. The antibodies from group O individuals, even before immunization, usually have some IgG anti- A,B, an antibody that cross-reacts with both A and B structures. Lab significance of naturally occurring antibodies: Used for reverse grouping as a mean of confirming the red cell phenotype  Immune anti-A and anti-B are produced after immunization with red blood cells or blood group substances or vaccinations. Following immunization, the thermal characteristics of the antibodies change, Immune antibodies are always warm reacting. These antibodies are commonly IgG, although some IgM antibodies may also develop, usually in the early phase of an immune response.  Naturally occurring Immune antibodies antibodies Present in plasma of subjects Develop due to introduction who lack the corresponding of RBC antigen which is antigen e.g Anti-A & anti-B normally absent in the subject as in case of transfusion IgM mainly IgG mainly They are cold antibodies. They are warm antibodies. They react at cold They react at 370C temperature 40C In other words: Red cell antigens and blood group antibodies IMP ********* Blood group antibodies The ABO blood group antigens are unusual in that naturally occurring antibodies – usually immunoglobulin M (IgM) and rarely IgG – occur in the plasma of subjects who lack the corresponding antigen, even if they have not been transfused or been pregnant. The origin of these antibodies is thought to be immunological recognition of bacterial cell wall glycoproteins in the gut that are similar to AB antigens and, consistent with this hypothesis, antibodies typically arise in the first few months of life as the bowel is colonised by normal bacterial flora. The most important of these natural antibodies are anti-A and anti-B. They are usually IgM, and react optimally at cold temperatures (4°C) so, although reactive at 37°C, they are called cold antibodies Red cell antigens and blood group antibodies IMP Blood group antibodies Immune antibodies against non-ABO system antigens, in contrast, develop in response to the introduction by transfusion or by transplacental passage during pregnancy – of red cells possessing antigens that the subject lacks. These antibodies are commonly IgG, although some IgM antibodies may also develop, usually in the early phase of an immune response. Immune antibodies react optimally at 37°C (warm antibodies). Only IgG antibodies are capable of transplacental passage from mother to fetus and the most important immune antibody is the Rh antibody, anti-D.  ABO grouping Forward Reversed Group Anti-A Anti-A1 Anti-B A cells B cells O cells - - - + + - O + + - - + - A1 + - - -/+ + - A2 - - + + - - B + + + - - - A1B + - + -/+ - - A2B  Naturally occurring Group Genotype antibodies O Anti-A ,B O/O A1 Anti-B A1/A1, A1/O,A1/A2 A2 Anti-B,anti-A1(1-8%) A2/A2, A2/O B Anti-A B/B, B/O A1B - A1/B A2B anti-A1(35%) A2/B  In the past group O donors called universal donors i.e. they give blood to group A, B and AB. Person with blood group O contain anti-A and anti-B which will react with the cells of the recipients. If the recipients take small amount of O blood, there will be neutralization of the antibodies. If the recipients take O blood contain immune antibodies, these antibodies will attack cells of the recipients lead to severe acute hemolytic reaction. So, transfusion of blood group O to non- O recipients should be discouraged. 1. ABO incompatible transfusion reactions (severe IVH). Major incompatibility (Antibodies of recipient destroy RBC of donor) Minor incompatibility (Antibodies of donor destroy RBC of recipient ) 2. ABO Haemolytic disease of the newborn (baby with A or B blood group, mother O group with immune antibodies). 3. Transplantation (kidney, liver, heart): Solid organ transplantation Summary Genes at three separate loci control the occurrence and location of ABH antigens. The presence or absence of the A, B, and H antigens is controlled by the H and ABO genes. The presence or absence of the ABH antigens on the red blood cell membrane is controlled by the H gene that is responsible for formation of the basic unite for A and B antigens The presence or absence of the ABH antigens in secretions is indirectly controlled by the Se gene. Blood group antigens are actually sugars attached to the red blood cell. The type of sugar added determines the blood group. Humans with AB-type blood contain both A-type and B-type enzymes. While humans with O-type blood lack both types of enzymes  Distribution of A, B and H antigens They are widely distributed in the body 1- WBC 2- Platelets 3- Epidermal and other tissue cells 4- Plasma (in alcohol soluble form) 5- In saliva and other secretions of ABH secretors In the 80% of the population who possess secretor genes, these antigens are also found in soluble form in secretions and body fluids (e.g. plasma, saliva, semen and sweat). References Immunohematology for medical laboratory technicians, 2010 Success in clinical laboratory sciences; 2020, fifth edition Hoffbrand’s essential hematology eighth edition (2020)