Blood Group dr. Husnil Kadri, M.Kes
ABO BLOOD GROUP History • Landsteiners discovered the ABO Blood Group System in 1901 • He and five co-workers began mixing each others red blood cells and serum together and accidentally performed the ABO groupings. • Main Phenotypes (A, B, AB, O) ABO gene located on long arm of chromosome 9
History of Blood Groups and Blood Transfusions (Cont.) • Karl Landsteiner discovered that blood clumping was an immunological reaction which occurs when the receiver of a blood transfusion has antibodies against the donor blood cells. • Karl Landsteiner's work made it possible to determine blood types and thus paved the way for blood transfusions to be carried out safely. For this discovery he was awarded the Nobel Prize in Physiology or Medicine in 1930.
Allele from the mother Allele from the father Genotype ofoffspring Blood types ofoffspring A A AA A A B AB AB A O AO A B A AB AB B B BB B B O BO B O O OO O Inheritance of ABO Groups
Blood Transfusions A blood transfusion is a procedure in which blood is given to a patient through an intravenous (IV) line in one of the blood vessels. Blood transfusions are done to replace blood lost during surgery or a serious injury. A transfusion also may be done if a person’s body can't make blood properly because of an illness. Rh + Can receive + or - Rh - Can only receive -
Significance of ABO Group • ABO mismatched transfusions: • Rare • May be life threatening • Can be caused by technical or clerical error • Intravascular haemolysis • More severe in group O patients
The Rh(D) Antigen • RH is the most complex system, with over 45 antigens • Discovered in 1940 after work on Rhesus monkeys • Subsequently discovered to be unrelated to monkeys • RH gene located on short arm of chromosome 1
Rh antigens are transmembrane proteins with loops exposed at the surface of red blood cells. • They appear to be used for the transport of carbon dioxide and/or ammonia across the plasma membrane. • RBCs that are "Rh positive" express the antigen designated D.
Simple Genetics of Rh(D) • 86% of caucasians are Rh(D) pos • The antithetical antigen d has not been found • The d gene is recessive: • Dd, dD, DD, persons are Rh(D) pos • Only dd persons are Rh(D) neg
Significance of Rh(D) • 80% of Rh(D) neg persons exposed to Rh(D) pos blood will develop anti-D • Anti-D can also be stimulated by pregnancy with an Rh(D) positive baby • Sensitisation can be prevented by the use of anti-D immunoglobulin, antenatally and post natally • Rh(D) neg females of childbearing potential should never be given Rh(D) positive blood products
Inheritance of ABO and Rh(D) Mother Group A AO Rh(D) pos Dd Father Group B BO Rh(D) pos Dd Group A AO Rh(D) pos Dd Group B BO Rh(D) pos Dd Group O OO Rh(D) neg dd
A person with Rh- blood can develop Rh antibodies in the blood plasma if he or she receives blood from a person with Rh+ blood, whose Rh antigens can trigger the production of Rh antibodies. • A person with Rh+ blood can receive blood from a person with Rh- blood without any problems.
Why is an Rh incompatibility so dangerous during pregnancy? • Most anti-A or anti-B antibodies are of the IgM class (large molecules) and these do not cross the placenta. • In fact, an Rh−/type O mother carrying an Rh+/type A, B, or AB foetus is resistant to sensitisation to the Rh antigen. • Her anti-A and anti-B antibodies destroy any foetal cells that enter her blood before they can elicit anti-Rh antibodies in her.
Rh incompatibility during pregnancy (cont.) • This phenomenon has led to an effective preventive measure to avoid Rh sensitisation. • Shortly after each birth of an Rh+ baby, the mother is given an injection of anti-Rh antibodies (or Rhogam). • These passively acquired antibodies destroy any foetal cells that got into her circulation before they can elicit an active immune response in her.
The ABO Antigens • Added to Proteins or Lipids in Red Cells • Substrate Molecule is H (fucose) • A antigen is N-acetyl-galactosamine (GalNAc) • B antigen is Galactose (Gal) • A and B genes code for transferase enzymes
H antigen • The H antigen is the foundation upon which A and B antigens are built • A and B genes code for enzymes that add an immunodominant sugar to the H antigen • Immunodominant sugars are present at the terminal ends of the chains and confer the ABO antigen specificity
Formation of the H antigen RBC Glucose H antigen Galactose N-acetylglucosamine Galactose Fucose
A and B Antigen • The “A” gene codes for an enzyme (transferase) that adds N-acetylgalactosamine to the terminal sugar of the H antigen • N-acetylgalactosaminyltransferase • The “B” gene codes for an enzyme that adds D-galactose to the terminal sugar of the H antigen • D-galactosyltransferase
Formation of the A antigen RBC Glucose Galactose N-acetylglucosamine Galactose N-acetylgalactosamine Fucose
Formation of the B antigen RBC Glucose Galactose N-acetylglucosamine Galactose Galactose Fucose
Genetics • The H antigen is found on the RBC when you have the Hh or HH genotype, but NOT from the hh genotype • The A antigen is found on the RBC when you have the Hh, HH, and A/A, A/O, or A/B genotypes • The B antigen is found on the RBC when you have the Hh, HH, and B/B, B/O, or A/B genotypes
Blood Group O people have red blood cells rich in H antigen. Why? Neither the A or B genes have converted the H antigens to A or B antigens - just a whole bunch of H! O allele at the ABO locus (amorph) It does not alter the structure of H substance.
Donor Nucleotides & Immundominant Sugars responsible for H, A, and B Ags specificity
ABO Antigens in Secretions • Secretions include body fluids like plasma, saliva, synovial fluid, etc • Blood Group Substances are soluble antigens (A, B, and H) that can be found in the secretions. This is controlled by the H and Se genes
Secretor Status • The secretor gene consists of 2 alleles (Se and se) • The Se gene is responsible for the expression of the H antigen on glycoprotein structures located in body secretions • If the Se allele is inherited as SeSe or Sese, the person is called a “secretor” • 80% of the population are secretors
Secretors • Secretors express soluble forms of the H antigen in secretions that can then be converted to A or B antigens (by the transferases) • Individuals who inherit the sese gene are called “nonsecretors” Secretions include saliva, urine, tears, bile, amniotic fluid, breast milk, exudate, and digestive fluids.
Lewis (Le) • The Lewis Blood Group System is mentioned here because it is related to secretor status • Lewis antigens are plasma antigens formed by tissues and are released into plasma where they adsorb onto the RBCs • Consists of 2 antigens • Lea • Leb
ABO Subgroups • ABO subgroups differ in the amount of antigen present on the red blood cell membrane • Subgroups have less antigen • Subgroups are the result of less effective enzymes. They are not as efficient in converting H antigens to A or B antigens (fewer antigens are present on the RBC) • Subgroups of A are more common than subgroups of B
Subgroups of A • The 2 principle subgroups of A are: A1 and A2 • Both react strongly with reagent anti-A • To distinguish A1 from A2 red cells, the lectin Dolichos biflorus is used (anti-A1) • 80% of group A or AB individuals are subgroup A1 • 20% are A2 and A2B
B Subgroups • B subgroups occur less than A subgroups • B subgroups are differentiated by the type of reaction with anti-B, anti-A,B, and anti-H • B3, Bx, Bm, and Bel
Other ABO conditions • Bombay Phenotype (Oh) • Inheritance of hh • The h gene is an amorph and results in little or no production of L-fucosyltransferase • Originally found in Bombay (now Mumbai) • Very rare (130 worldwide)
ABO antibodies • group A serum contains anti-B • group B serum contains anti-A • group AB serum contains no antibodies • group O serum contains anti-A, anti-B, and anti-A,B
Anti-A1 • Group O and B individuals contain anti-A in their serum • However, the anti-A can be separated into different components: anti-A and anti-A1 • Anti-A1 only agglutinates the A1 antigen, not the A2 antigen • There is no anti-A2.
Anti-A,B • Found in the serum of group O individuals • Reacts with A, B, and AB cells • Predominately IgG, with small portions being IgM • Anti-A,B is one antibody, it is not a mixture of anti-A and anti-B antibodies
ABO antibodies • IgM is the predominant antibody in Group A and Group B individuals • Anti-A • Anti-B • IgG (with some IgM) is the predominant antibody in Group O individuals • Anti-A,B (with some anti-A and anti-B)
ABO Antibodies • Usually present within the first 3-6 months of life • Stable by ages 5-6 years • Decline in older age • Newborns may passively acquire maternal antibodies (IgG crosses placenta)
Laboratory Testing: ABO typing
The ABO Blood Group System Laboratory Determination of the ABO System
Serology:This is a direct detection of the ABO antigens. It is the main method used in blood transfusion centres and hospital blood banks. This form of testing involves two components: a)Antibodies that are specific at detecting a particular ABO antigen on RBCs. b)Cells that are of a known ABO group that are agglutinated by thenaturally occurring antibodies in the person's serum.
Illustration of the forward and reverse grouping reaction patterns of the ABO groups using a blood group tile http://www.bh.rmit.edu.au/mls/subjects/abo/resources/genetics1.htm
RESOURCES • Aldahr MHS. ABO Blood Group. Faculty of Applied Medical Sciences Blood Bank Medical Tecnology. download 2011 • Giacobbe. ABO & Rh(D) Blood Groups. Anatomy & Physiology. Unit 9 – Circulatory System.download 2011 • Musani MI. Blood groups and Rhesus factor. Download 2011 • Trimpe T. Blood Basics. Forensic Science.2006 • Wilkins RN. ABO Blood Group System. University of Mississippi Medical Center. Download 2011.