ABO system of Blood grouping

ABO BLOOD GROUP SYSTEM: 

ABO BLOOD GROUP SYSTEM DR. PRABESH KUMAR CHOUDHARY National Academy of Medical Science Dept. of Pathology Resident, 2 nd Year Kathmandu

History: Karl Landsteiner: 

History : Karl Landsteiner Discovered the ABO Blood Group System in 1901 He and his five co-workers began mixing each others red cells and serum together and inadvertently performed the first forward and reverse ABO groupings. http://www.nobelpreis.org/castellano/medizin/images/landsteiner.jpg

ABO antigens:: 

ABO antigens: Biochemical & Genetic Considerations

Biochemistry of ABO Antigens: 

Biochemistry of ABO Antigens Location: Embryos >>all endothelial & epithelial cells except CNS; Adults >>RBCs, plasma, lymphocytes, platelets & secretions; Granulocytes >> I antigen Antigen in platelet & lymphocyte>> adsorption from plasma Carbohydrate and protein antigens: Immunodominant sugar: specificity “I” activity Vs “i” activity: I antigen Type 1 chain precursor: secretion Type 2 chain precursor: RBCs

Page-621, Figure 34–2 Synthesis of type 1 and type 2 chain H and AB antigens. Type 1 chain and type 2 chain precursors (underlined) are fucosylated by FUT1 and FUT2 fucosyltransferases to form H antigen. H antigen then serves as a substrate for A and B glycosyltransferases. The terminal carbohydrate epitopes denoting blood group H, A, and B antigens are highlighted in amber. Fuc = fucose; Gal = galactose; GalNAc = N-acetylgalactosamine; R = other oligosaccharide.: 

Page-621, Figure 34–2 Synthesis of type 1 and type 2 chain H and AB antigens. Type 1 chain and type 2 chain precursors (underlined) are fucosylated by FUT1 and FUT2 fucosyltransferases to form H antigen. H antigen then serves as a substrate for A and B glycosyltransferases. The terminal carbohydrate epitopes denoting blood group H, A, and B antigens are highlighted in amber. Fuc = fucose; Gal = galactose; GalNAc = N-acetylgalactosamine; R = other oligosaccharide.

Location: 

Location The presence or absence of the ABH antigens on the red blood cell membrane is controlled by the H gene(19q13.3)>>FUT1 The presence or absence of the ABH antigens in secretions is indirectly controlled by the Se gene(19q13.3)>>FUT2 They differ in certain base sequence and thus the No of amino acids A, B and O genes: 9q34

ABO Antigen Genetics: 

ABO Antigen Genetics I gene- I and i alleles H gene – H and h alleles (h is an amorph ) Se gene – Se and se alleles (se is an amorph) ABO genes – A, B and O alleles: 7 exons; A & B gene products differ in their aminoacid sequence at position 176, 235, 266 & 268 O gene is similar to A gene except single base deletion at 261>> frameshift mutation

H Antigen: 

H Antigen The H gene codes for an enzyme that adds the sugar fucose to the terminal sugar of a precursor substance (PS) The precursor substance (proteins and lipids) is formed on an oligosaccharide chain (the basic structure)

RBC Precursor Structure: I antigen: 

RBC Precursor Structure: I antigen Glucose Galactose N-acetylglucosamine Galactose Precursor Substance (stays the same) RBC

Formation of the H antigen: 

Formation of the H antigen Glucose Galactose N-acetylglucosamine Galactose H antigen RBC Fucose

A and B Antigen: 

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-acetylgalactosaminyl transferase The “ B ” gene codes for an enzyme that adds D-galactose to the terminal sugar of the H antigen D-galactosyl transferase

Formation of the A antigen: 

Formation of the A antigen Glucose Galactose N-acetylglucosamine Galactose RBC Fucose N-acetylgalactosamine

Formation of the B antigen: 

Formation of the B antigen Glucose Galactose N-acetylglucosamine Galactose RBC Fucose Galactose

Donor Nucleotides & Immundominant Sugars responsible for H, A, and B Ags specificity : 

Donor Nucleotides & Immundominant Sugars responsible for H, A, and B Ags specificity Antigen Immunodominant sugar Nucleotide Glcosyltransferase Gene H L-fucose Guanosine GDP-FUC L- fucosyl trnsferase H A N-acetyl-D-galactoseamine Uridine UDP-GALNAC N- acetylgalactosaminyl transferase A B D-galactose Uridine UDP-GAL D- galactosyl transferase B

ABO Genetics: 

ABO Genetics Hh gene – H and h alleles ( h is an a morph) Se gene – Se and se alleles ( se is an amorph) ABO genes – A, B and O alleles Controls presence of H, A, and B antigens on both RBCs and in Secretions Controls presence of H antigen in the secretions Inherit 1 gene from each parent that codes for an enzyme that adds a sugar to the H antigen

ABO INHERITANCE: 

ABO INHERITANCE T2 Dad = A/O and Mom = B/O Mom B O Dad A A / B A / O O O / B O/ O

Genetics: 

Genetics The H antigen >> Hh or HH genotype, but NOT from the hh genotype The A antigen >> Hh, HH, and A/A, A/O, or A/B genotypes The B antigen >> Hh, HH, and B/B, B/O, or A/B genotypes

H antigen: 

H antigen Certain blood types possess more H antigen than others: O>A 2 >B>A 2 B>A 1 >A 1 B Greatest amount of H Least amount of H

: 

Group O Group A Many H antigen sites Fewer H antigen sites A A A A A Most of the H antigen sites in a Group A individual have been converted to the A antigen

ABO Antigens in Secretions: 

ABO Antigens in Secretions Secretions include body fluids like plasma, saliva, synovial fluid, etc Soluble antigens in the secretions Controlled by the H and Se genes

Secretor Status: 

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 Secretors express soluble forms of the H antigen in secretions that can then be converted to A or B antigens Individuals who inherit the sese gene are called “nonsecretors” The individuals do not have any blood group antigens in the secretions

PowerPoint Presentation: 

ABO groups of the offspring from the various possible ABO mating Phenotypes Genotype offspring AxA AAxAA A (AA) AAxAO A (AA or AO) AOxAO A (AA or AO),O(OO) BxB BBxBO B (BB or BO) AxAB AAxAB AB (AB) or A (AA) AOxAB AB (AB), A (AA, AO), B(BO)

Altered ABH antigen expression: 

Altered ABH antigen expression AML>> reduced expression Acquired B antigen in A individuals>> Deacetylase (severe infections, GI lesion and malignancies) Group B activity due to adsorption of material from organisms e.g. E. Coli 86 and proteus vulgaris

ABO Subgroups: 

ABO Subgroups 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

O Subgroups: 

O Subgroups O1 & O1var>> Deletion mutations O2 >> European population; Single missense mutation at position 268

Subgroups of A: 

Subgroups of A The 2 principle subgroups of A are: A 1 and A 2 A2 allele>>Pro156Leu substituition, Single nucleotide deletion (reduced activity) Both react strongly with reagent anti-A To distinguish A 1 from A 2 red cells, the lectin Dolichos biflorus is used (anti-A 1 ) 80% of group A or AB individuals are subgroup A 1 20% are A 2 and A 2 B

A2 Phenotype: 

A 2 Phenotype Why is the A 2 phenotype important? A 2 and A 2 B individuals may produce an anti-A 1 This may cause discrepancies when a crossmatch is done (incompatibility) What’s the difference between the A 1 and A 2 antigen? It’s quantitative The A 2 gene doesn’t convert the H to A very well The result is fewer A 2 antigen sites compared to the many A 1 antigen sites

A1 and A2 Subgroups*: 

A 1 and A 2 Subgroups* Anti-A antisera Anti-A 1 antisera Anti-H lectin ABO antibodies in serum # of antigen sites per RBC A 1 4+ 4+ 0 Anti-B 900 x10 3 A 2 4+ 0 3+ Anti-B & anti-A 1 250 x10 3 *Adapted from Flynn, J. (1998). Essentials of Immunohematology

Other A subgroups: 

Other A subgroups There are other additional subgroups of A A int (intermediate), A 3 , A x , A m , A end , A el , A bantu (single point mutations) A 3 red cells cause mixed field agglutination when polyclonal anti-A or anti-A,B is used Mixed field agglutination appears as small agglutinates with a background of unagglutinated RBCs They may contain anti-A 1

B Subgroups: 

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 B 3 , B x , B m , and B el Others>>> cis-AB, B(A)

Other ABO conditions: 

Other ABO conditions Bombay Phenotype (O h ) 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: 0.0004% worlwide, 0.01% in Bombay Para Bombay phenotype: decreased expression due to mutation

Bombay: 

Bombay The hh causes NO H antigen to be produced Results in RBCs with 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??

ABO Blood Group:: 

ABO Blood Group: ABO Antibodies

Landsteiner’s Rule:: 

Landsteiner’s Rule : Normal, Healthy individuals possess ABO antibodies to the ABO antigen absent from their RBCs

ABO: 

ABO -The ABO Blood Group System does NOT require the presence of a foreign red blood cell for the production of ABO antibodies ABO antibodies are “non-red blood cell stimulated” probably from environmental exposure e.g. ABO like bacterial polysaccharide”

ABO antibodies: 

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: 

Anti-A 1 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-A 1 Anti-A 1 only agglutinates the A 1 antigen, not the A 2 antigen There is no anti-A 2 .

Anti-A,B: 

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: 

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 antibody facts: 

ABO antibody facts Reactions phase: Room temperature Complement can be activated with ABO antibodies (mostly IgM, some IgG) High titer: react strongly (4+)

ABO Antibodies: 

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) Reverse grouping (with serum) should not be performed on newborns or cord blood

Nature of antibodies: 

Nature of antibodies Non-red blood cell stimulated: Red blood cell stimulated Antibodies formed as a result of transfusion, etc Whether Ig M is always the first antibody is not clear Usually IgG Active at 37°C Can occur in group O (may occur in group A or B)

PowerPoint Presentation: 

Thanks for your Attention!!