Introduction to the ABO Blood Group Justin R. Rhees, M.S., MLS(ASCP) - - PowerPoint PPT Presentation

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Introduction to the ABO Blood Group Justin R. Rhees, M.S., MLS(ASCP) - - PowerPoint PPT Presentation

Jan 18, 2023 654 likes •1.29k views

Introduction to the ABO Blood Group Justin R. Rhees, M.S., MLS(ASCP) CM , SBB CM Objectives 1. Describe the biochemistry and production of the A, B, and H antigens. 2. Compare and contrast the subgroups of the A and B blood types. 3. Describe

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Justin R. Rhees, M.S., MLS(ASCP)CM, SBBCM

Introduction to the ABO Blood Group

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SLIDE 2
  • 1. Describe the biochemistry and production of the A,

B, and H antigens.

  • 2. Compare and contrast the subgroups of the A and B

blood types.

  • 3. Describe two lectins that can be used to aid in

correct ABO typing.

  • 4. Given the results of forward and reverse ABO typing,

correctly interpret the patient’s ABO group and identify patterns of discrepancy.

Objectives

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ABO Typing

Anti-A: + Anti-B: 0 A antigen detected

Red blood cells Anti-A Anti-B Hemagglutination No Hemagglutination

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ABO Typing

Anti-A: 0 Anti-B: 0 Neither A nor B antigens detected

Anti-A Anti-B

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ABO Typing

Anti-A: + Anti-B: + A and B antigens detected

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Forward Type

  • Detection of antigens on the patient’s red

cells:

Anti-A Anti-B Type + A

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SLIDE 7

Forward Type

  • Detection of antigens on the patient’s red

cells:

Anti-A Anti-B Type + B

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SLIDE 8

Forward Type

  • Detection of antigens on the patient’s red

cells:

Anti-A Anti-B Type + + AB

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SLIDE 9

Forward Type

  • Detection of antigens on the patient’s red

cells:

Anti-A Anti-B Type O

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Reverse Typing

Plasma or serum (Contain antibodies) Erythrocytes (Express antigens) IgM IgG IgA

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Reverse Typing

Plasma or serum (Contain antibodies) Erythrocytes (Express antigens) IgM IgG IgA

Type A Antibodies to Type B

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Reverse Typing

Plasma or serum (Contain antibodies) Erythrocytes (Express antigens) IgM IgG IgA

Type B Antibodies to Type A

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Reverse Typing

Plasma or serum (Contain antibodies) Erythrocytes (Express antigens)

Type AB Do not form antibodies to A or B antigens

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Reverse Typing

Plasma or serum (Contain antibodies) Erythrocytes (Express antigens) IgM IgG IgA

Type O Antibodies to both A and B

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Forward and Reverse Type

Anti-A against

  • Pt. RBC

Anti-B against

  • Pt. RBC

Forward Type

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SLIDE 16

Forward and Reverse Type

Anti-A against

  • Pt. RBC

Anti-B against

  • Pt. RBC
  • Pt. Plasma

against A RBC

  • Pt. Plasma

against B RBC Forward Type Reverse Type

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SLIDE 17

Forward and Reverse Type

Anti-A against

  • Pt. RBC

Anti-B against

  • Pt. RBC
  • Pt. Plasma

against A RBC

  • Pt. Plasma

against B RBC Interp.

+ + A

Forward Type Reverse Type

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SLIDE 18

Forward and Reverse Type

Anti-A against

  • Pt. RBC

Anti-B against

  • Pt. RBC
  • Pt. Plasma

against A RBC

  • Pt. Plasma

against B RBC Interp.

+ + B

Forward Type Reverse Type

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SLIDE 19

Forward and Reverse Type

Anti-A against

  • Pt. RBC

Anti-B against

  • Pt. RBC
  • Pt. Plasma

against A RBC

  • Pt. Plasma

against B RBC Interp.

+ + AB

Forward Type Reverse Type

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SLIDE 20

Forward and Reverse Type

Anti-A against

  • Pt. RBC

Anti-B against

  • Pt. RBC
  • Pt. Plasma

against A RBC

  • Pt. Plasma

against B RBC Interp.

+ + O

Forward Type Reverse Type

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SLIDE 21

ABORh

Anti-A Anti-B Anti-D (Rh) A1 Cell B Cell

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Basic ABO Biochemistry:

ABH antigen formation

  • Mendelian

– A and B are codominant

  • Chromosome 9

– Over 200 alleles have been identified at the ABO locus!

  • O gene is an amorph

– O/O inheritance produces O phenotype

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Inheritance question

  • My mother and father are both A positive
  • My sister is O negative
  • Possible?

A O A A/A A/O O A/O O/O

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Inheritance question

  • My mother and father are both A positive
  • My sister is O negative
  • Possible?

A O A A/A A/O O A/O O/O D d D D/D D/d d D/d d/d

D=Rh antigen d=lack of Rh antigen

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Basic ABO Biochemistry:

ABH antigen formation

  • Glycosyltransferases: add sugars to a basic

precursor substance.

  • 37th day of fetal life.
  • Neonate: 25-50% antigen sites on RBC
  • How are these antigens formed?
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SLIDE 26

Ceramide Glucose D-Galactose (GAL) N-acetylglucosamine (GLNAC) D-Galactose (GAL)

RBC membrane Type 2 Precursor Chain

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Ceramide Glucose D-Galactose (GAL) N-acetylglucosamine (GLNAC) D-Galactose (GAL)

L-Fucose H antigen

RBC membrane

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Ceramide Glucose D-Galactose (GAL) N-acetylglucosamine (GLNAC) D-Galactose (GAL)

L-Fucose A gene

RBC membrane

N-acetylgalacosaminyl transferase

N-acetylgalactosamine

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SLIDE 29

Ceramide Glucose D-Galactose (GAL) N-acetylglucosamine (GLNAC) D-Galactose (GAL)

L-Fucose B gene

RBC membrane

D-galactosyl transferase

D-Galactose

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SLIDE 30

Ceramide Glucose D-Galactose (GAL) N-acetylglucosamine (GLNAC) D-Galactose (GAL)

L-Fucose O/O genes?

RBC membrane

Result: Lots of unmodified H antigens on the RBC

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hh genotype

  • The H gene is present in more than 99.99% of

the population. (HH or Hh)

  • The hh genotype is therefore extremely rare.
  • Known as Oh or the “Bombay” phenotype,

(hh) individuals may inherit ABO genes, but because the H antigen is not formed, no ABO expression can occur.

Genes: h/h, A/B

Neither A nor B antigens detected

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Oh Bombay phenotype

  • First reported by Bhende in 1952 in Bombay, India.

Approx 130 cases worldwide have been reported.

  • because of hh inheritance, ABO cannot be expressed.
  • No reactions with anti-A, anti-B, or anti-H
  • Bombay individuals produce anti-A, anti-B, anti-A,B,

and anti-H. They ABO type as O, but cannot receive O

  • blood. Why?

– A: Type O has the highest amount of H. Transfusion of type O blood would cause an immediate hemolytic transfusion reaction.

Oh individuals should only receive Oh donor blood

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Anti-H lectin

  • A lectin is a protein

that is capable of binding to a carbohydrate.

  • A lectin with anti-H

specificity can be derived from the seeds of the Ulex europaeus plant

Common gorse, Ulex europaeus

Photo credit: Creative Commons https://commons.wikimedia.org/wiki/File:Ulex_europaeus_flowers.jpg

Anti-H lectin will agglutinate Group O cells, but not Oh (Bombay) cells

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Early transfusion attempts

  • 1667 Jean-Baptiste Denis transfused blood

from a calf into “madman” Antoine Mauroy.

Image source: Wellcome Library Attribute: https://wellcomecollection.org/works/jj7nx247?query=blood+transfusion

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Last half of 19th Century

  • 1873, F. Gesellius estimated that 56% of

transfusions ended in death

Image Source: Science Museum, London Photo and Image Attributions: https://wellcomecollection.org/works/bndyugwh?query=blood+transfusion

  • J. H. Aveling ‘Immediate Transfusion’

Image Source: Wellcome Collection

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Karl Landsteiner

  • Karl’s serum

agglutinates my cells.

  • My serum does not

agglutinate Karl’s cells.

  • What are the

possible blood types?

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Karl Landsteiner

  • Karl’s serum

agglutinates my cells.

  • My serum does not

agglutinate Karl’s cells.

  • What are the

possible blood types?

Karl is type O. I am type A, B, or AB Karl is type A or B. I am type AB

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A Subgroups

  • A subgroups:

– A1 A2 A3 Ax Aend Am Ay Ael etc.

  • Approx. 80% of type A individuals are A1
  • Approx. 20% of type A individuals are A2
  • The remaining subgroups comprise 1%
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A1 and A2

  • Inheritance of an A1 gene elicits production of

high concentrations of α-3-N-acetylgalactosaminyltransferase

  • Converts almost all of the H precursor

structure to A1 antigens.

  • A1 antigens are more highly branched than the

“common A” structure shown previously

  • A2 type has fewer antigens per cell, only exist

as “common A”

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SLIDE 40

A1 and A2

  • The immunodominant sugar on both A1 and

A2 RBCs is N-acetyl-galactosamine; however, there are subtle antigenic differences which cause the body to discern self from non-self.

  • A1: 810,000 to 1,170,000 antigen sites
  • A2: 240,000 to 290,000 antigen sites
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A1 and A2

  • A1 subgroup has both

“common A” and A1

  • antigens. Most of the H

antigens have been converted.

  • A2 subgroup has only

“common A” antigens. More unconverted H antigens.

A1 A A1 A A A1 A1 A A A A A1

A= “Common A” antigens A1= highly branched A antigens A1 type A2 type

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Anti-A1

  • Because approximately 20% of type A

individuals are A2, we sometimes encounter anti-A1 in transfusion medicine.

  • Anti-A1 is non-RBC Immune, IgM, and usually

cold reacting. It is only considered clinically significant if it is reactive at 37°C.

  • Anti-A1 is produced by approx. 1-8% of A2

individuals.

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ABO Discrepancy

Anti-A Anti-B

+

A1 Cell B Cell

+ +

Forward Type Reverse Type

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Anti-A1 Lectin

  • A purified extract made from the seeds of the Dolichos biflorus

plant agglutinate red blood cells with A1 antigens present.

  • Note: there is no anti-A2 lectin. Why?

Blood Group Antigen Present Anti-A

(Anti-A plus Anti-A1)

Anti-A1 Lectin

A1 A1 A + + A2 A +

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Weak subgroups of A

  • As stated before, the prevalence of A subgroups
  • f A weaker than A1 and A2 is less than 1%

Subgroup Laboratory Results Number of A antigenic sites

A3

Mixed field reaction with anti-A and most anti-A,B reagents

35,000 per RBC

Ax

Characteristically not agglutinated with anti-A but do agglutinate with most examples of anti-A,B

4000

Aend

Mixed field reaction with anti-A and anti-A,B. Aend is inherited as an allele at the ABO locus. Anti-A1 is found in some sera. Only H is found in secretions.

3500

Am

Characteristically not agglutinated, or very weakly agglutinated by all anti-A and anti-A,B reagents. Usually do NOT produce anti-A1 in sera.

200-1900

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Weak subgroups of A

  • Fewer antigen sites on the RBC means weaker

reactions with antisera.

  • It is possible for an Ax donor to be mistyped as
  • O. This unit could then be transfused into an

O recipient, who has anti-A,B. The anti-A,B antibody in the recipient could agglutinate and lyse the donor Ax RBCs and cause intravascular hemolysis.

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Weak subgroups of B

  • Subgroups of B are very rare and less frequent

than A subgroups.

– B, B3, Bx, Bm, Bel, etc.

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AB subgroups

  • AB individuals can demonstrate subgroups of

A, B or both

– A1B, A2B, AxB, A1Bel, etc.

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Reactivity of anti-H lectin

O > A2 > B > A2B > A1 > A1B > Oh (Bombay)

Greatest amount of H Least amount of H

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ABO Discrepancies

  • All ABO Discrepancies must be resolved

prior to reporting a patient or donor ABO group.

  • Why investigate these discrepancies?
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Forward Type

Is there anything wrong with this picture?

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Mixed Field (MF) Reaction

Control tubes Patient tubes

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Case Study

A technologist reads and reports a patient’s blood type:

Anti-A Anti-B Anti-D A1 Cell B Cell 3+ 3+ 4+

Interpretation: AB Positive

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Case Study

A technologist reads and reports a patient’s blood type:

Anti-A Anti-B Anti-D A1 Cell B Cell 3+ 3+ 4+

Interpretation: AB Positive The sample is from an A positive patient undergoing a type B negative BMT. Lack of visible reverse type is due to immunosuppression. According to our protocols, the patient should be supported on irradiated, washed, O negative red cells.

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Question 1

Anti-A Anti-B A1 Cell B Cell

+ +

Forward Type Reverse Type

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Question 2

Anti-A Anti-B

+

A1 Cell B Cell

+

Forward Type Reverse Type

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Question 3

Anti-A Anti-B

+ +

A1 Cell B Cell Forward Type Reverse Type

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Question 4

Anti-A Anti-B

+

A1 Cell B Cell Forward Type Reverse Type

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Question 5

Anti-A Anti-B

+

A1 Cell B Cell

+ +

Forward Type Reverse Type

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Question 6

What do vampires put on their steak? Answer: A1

Image credit: Creative Commons

Attribute: https://commons.wikimedia.org/wiki/File:Little-vampire.svg

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References

  • Harmening DM, Ed. Modern Blood Banking

and Transfusion Practices, 6th Ed. F. A. Davis Company, Philadelphia. 2012.

  • Fung MK, Eder AF, Spitalnik SL, Westhoff CM.

AABB Technical Manual, 19th Ed. AABB Press. 2017