BB lecture 2

the first human blood group to be identified

ABO Blood Group System

what is unique about ABO blood group?

the only blood group that has naturally occurring Abs

• it doesnt require presence of foreign RBC ag to illicit the production of ABO Abs

Most significant blood group for transfusion practice!

For ABO Abs, what is the relation of specificity to the corresponding antigens that are present?

specificity is opposite to the corresponding ags that are present from RBCs

What type of antibodies are ABO antibodies?

non-red cell stimulated Abs - from environmental exposure

What are ABO Abs referred to as?

Expected antibodies

common isohemagglutinins found in ABO blood group

• anti-A & anti-B

• IgMs

What can be the range of the progressive results from the transfusion of incompatible RBCs?

intravascular hemolysis to renal failure to death

What is one of the primary foundations in pretransfusion testing and safe transfusion?

Detection of ABO incompatibility

Where is ABO compatibility also critical in?

transplant patients

What can occur if ABO incompatible organs are transplanted?

Acute humeral rejection that lead to graft rejection/failure (GVHD) and eventually death depending on what organ was transplanted

3 common allele system

A, B, H (O)

A & B genes are ___

O gene is ___

• co-dominant

• recessive & amorph

amorph

dosen’t produce transferase enzyme and results in NO detectable O ag

• O ag doesn’t exist, will be H ag

ABO genes are expressed as __

where is the locus located?

• co-dominant

• chromosome 9

if both parents are type A, can they produce a type O baby?

yes if both parents carry the O allele

ABO Phenotype Group

• O

• A

• B

• AB

What are the possible Genotype?

Possible Genotype

• HH (OO)

• AA or AO*

• BB or BO*

• AB

  when determining possible genotype, use heterozygous form * of genes

ABH =

ABO

• “O” contains H ag

• there is no “O” antigen

4 sugar chain for H precursor substance

which gene is amorph and very rare?

h

What gene is required for production of A or B antigens?

H gene

What does the H gene produce that adds L-fuctose (Fuc) to the precursor substance?

What is the result of of the attached L-fucose (Fuc)?

• a-2-L-fucosyltransferase

• H ag

H gene on precursor substance to form H antigen

Type of Oligosaccharide chain structures

Type 1: body fluids & secretions

• B1-3 linkages

Type 2: rbc body fluids & secretions

• B1-4 linkages

Which alleles and genes encode for glycosyl-transferases which add sugars to the H antigen?

A and B alleles / genes

Which gene produces the α-3-N-actetylgalactosaminyltransferase? What does this do?

A gene; adds the GalNAc (N-acetyl-D-galactosamine) sugar to the H ag

Which gene produces the α-3-D-galactosyltransferase? What does this do?

the B gene ; adds Gal (D-galactose) sugar to the H antigen

Which gene competes more efficiently for the H antigen? What is the result of this?

• B enzyme compete more efficiently for the H ag than the A enzyme.

  • As a result of this competition, the # of B ags > # of A ags

“A” ag biochemical structure

B ag biochemical structure

The more A and B antigens are produced, the more.....

H ag is converted.

What is the density of H ag on cells from greatest to least amounts?

O > A₂ > B > A₂B > A₁ > A₁B

Which H genotype is known as Bombay?

What is the ABO phenotype?

What is the RBC antigens absent on this?

What are the expected plasma antibodies?

hh

Oh

No A, B, or H

Potent Anti-H; Anti-A and Anti-B

What genes are found and located on chromosome 19?

• H (FUT 1)

• Se ( FUT 2)

Which gene is found and located on chromosome 9?

ABO

Se stands for?

se stands for?

• secretor; H substance found in secretions

• non-secretor; silent/amorph

which gene is silent/amorph?

h, O

Se has expression over the se amorph allele

• SeSe / Sese ~ 80% secretors of A, B, and / or H

  • most of us are secretors

• sese ~ 20% nonsecretors

  • doesnt secrete A, B, H

Glycolipids

imbedded in cell membranes

Glycoproteins

secreted into exocrine fluids

Fucosly-transferase adds ____ to make H antigen primarily on ____

• L-fucose

• Type-1 chain

distinction of ABH ags & ABH soluble substances

What is not produced in the hh genotype, aka Bombay? (Oh)

• No L-fucosyl-transferase produced

• No H substance / no H ag

• No A or B ags present on RBCs

• Only precursor substance found on RBCs

Bombay (Oh) Phenotype:

• No production of L-fucosyl-transferase and no H antigen produced results in what?

RBCs with no H, A, or B ag

Bombay RBCs will NOT agglutinate with reagent Anti-A, Anti-B, Anti-A,B, or anti-H results in the patient typing as an ....?

O

What naturally occurring antibodies are found in the plasma of Bombay phenotype (Oh) individuals?

Anti-A, Anti-B, Anti-A,B, and a potent Anti-H

• Agglutinating ALL ABO blood groups

What do both A1 and A2 both encode for? What does this do to the H antigen?

α-3-N-acetyl-galactose-aminyl-transferase ; puts an immunodominant sugar

N-acetyl-D-galactose on H antigen

Which A subgroup is more potent?

A₁

A₁A₂ genotype = ?

A₁ phenotype

A₂A₂ or A₂O genotype = ?

A₂ phenotype

Why do most group A infants appear to be A2 at birth?

ABH antigens not yet fully developed

Unlike the A subgroup, what does not exist in reference to the B subgroups?

"anti-B1" does NOT exist

For typing a patient's ABO blood type, testing BOTH the patient's ___ & ___ is required

RBC & the plasma / serum is required

What is known as the "Forward" type/group?

RBC testing

What is known as the "Reverse" type/group?

plasma / serum testing

Which reagent is known as "group O" typing sera

What does it contain?

Anti-A,B reagent

• contains anti-A,B of IgG2 subclass

Forward types give what level of reactions?

4+

What is detected in reverse typing?

circulating Abs to A, B, AB, or H

Reverse typing should not be performed on children that are younger than....

6 months

Bombay Phenotype lacks what?

lacks H antigen on RBC, so no A,B,H

• needed for A or B ags

order of adding reagents

Forward

• Add 1 drop of reagent antisera + 1 drop of patient cells; mix;

  spin; & read

Reverse

• Add 2 drop of patient serum + 1 drop of red cell reagent; mix;

  spin; & read

always add clear substance first! Reagent/serum first then red cells last

ABO testing: Reverse Type/Group

ABO antibodies are also known as

isohemagglutinins

What type of immunoglobulins are ABO antibodies (Abs)?

• IgM

  • found in groups A & B individuals

  • BOTH IgM and IgG2 subclass found in group O individuals

What are the key characteristics of ABO antibodies in healthy individuals?

naturally occurring, cold to thermo-tolerant,

cause strong (4+) agglutination at immediate spin/room temp, and are present in all healthy people against the ABO antigens they lack.

Type O people have higher titers of which antibody?

Type O individuals have higher titers of anti-A than do type B people

What serious conditions can ABO antibodies cause?

• Serious/fatal transfusion reactions if incompatible blood is transfused

• Severe Hemolytic Disease of the Fetus and Newborn (HDFN)

Where is HDFN usually seen in?

Group O mothers giving birth to Group A neonates/babies

How does age affect ABO antibody development?

Before 3–6 months

• Very low ABO antibody titers due to immature/undeveloped immune system

• DONT perform reverse typing in babies <6 months old

By age 5–10: Adult levels of ABO antibodies are generally reached

After 65 years: ABO antibody titers may decrease due to aging and weakened immunity

ABO typing discrepancies

• Technical / Clerical errors

• RBC reactivity with antisera:

  • Weak or mixed field

  • Unexpected reaction

• Plasma / serum reactivity with reagent RBCs:

  • Unexpected reaction

  • Missing or weak plasma reaction

Which group discrepancy has the following:

• Reason:

  • weak reacting or missing antibodies

• Conditions

  • Chimerism

  • New born infants

  • Elderly patients

  • Hypogammaglobulinemia (leukemia, immunodeficiency disease)

Group I Discrepancy

Which group discrepancy has the following

• Reason:

  • weak reacting or missing antigens

• Conditions:

  • Subgroups of A or B

  • Leukemia: excess amount of B

  • Acquired B phenomenon (in gram negative septicemia, intestinal obstruction and cancer of colon or rectum)

Group II Discrepancy

Which group discrepancy has the following:

• Reason:

  • Protein/plasma abnormality leading to rouleaux formation

• Conditions:

  • elevated globulin level (in multiple myeloma, Waldenstrom macroglobulinemia, plasma cell dyscrasia, Hodgkin lymphoma)

  • Plasma expanders like dextran, polyvinyl pyrrolidone

  • Wharton's Jelly (in cord blood)

Group III Discrepancy

What group discrepancy has the following reasons and conditions:

• Reason:

  • Miscellaneous problems

• Conditions:

  • Exposure of hidden erythrocyte T antigen (Polyagglutination)

  • cold and warm autoantibody (AIHA)

  • Transfused foreign antigen

  • Unexpected ABO iso-agglutinin and alloantibody

  • Antibody other than anti-A and anti-B

  • cis - AB individuals

Group IV discrepancy