CLS 306 (BB) Lecture 2 - ABO Blood Group System

Naturally occurring Abs

The ABO blood group system is teh first human blood group to be identified and it is unique in that it is the only group to have (——); it does NOT require the presence of a foreign RBC Ag to illicit the production fo the ABO Abs

Isohemagglutinins

ABO Abs are also known as… and are probably developed from environmental exposure

TJC and CAP Proficienct tests

These tests require that ABO typing is 100% correct/accurate at all times

Graft rejection/failure (GVHD)

If ABO-incompatible organs are transplanted, acute humeral rejection could occur leading to (——) which ocould result in the recipient’s death, depending on what organ was transplanted

Amorph

The “O” gene is recessive and is considered an (——) gene since it does not produce a transferase enzyme and results in no detectable O Ag

Chromosome 9

ABO locus is on…

Carbohydrate

ABH antigens have a (——) structure

Glycosyle-transferases

For ABH antigens, specific (——) add individual sigars sequentially to sites on sugar chains on the common precursor substances; A and B alleles/genes encode for this, and it adds sugars to the H Ag

• Glucose (Glu)

• Galactose (Gal)

• N-acetylglucosamine (GlcNAc)

• Galactose (Gal)

What is the 4 sugar chain of the H precursor substance in ABH Ag

⍺-2-L-fucosyltransferase

H gene produces the (——) that adds L-fucose to the precursor substance

L-fucose (Fuc)

The H Ag is the result of the attached (——) to the precursor substance

• ⍺-3-N-acetylgalactosaminyltransferase

• N-acetyl-D-galactosamine (GalNAc)

The A gene produces the (——), which adds the (——) sugar to the H Ag

• ⍺-3-D-galactosyltransferase

• D-galactose (Gal)

The B gene produces the (——) that adds the (——) sugar to the H Ag

• B enzyme

• A enzyme

• Less than

When both A and B genes are present to produce the AB phenotype, the (——) enzyme seems to compete more efficiently for the H Ag than the (——). As a result of this competition, the number of A Ag on the RBC are (>/</=) the number of B Ag

O > A₂ > B > A₂B > A₁ > A₁B

The more A or B Ags produced, the more H Ag is converted. List the ABO blood groups from most H Ag to least H Ag

• Genotype: hh (Bombay)

• Phenotype: O_h

What is the genotype and phenotype for the blood type with no A, B, or H Ags with potent anti-H, ant-A, and anti-B Abs

Chromosome 19

H gene (FUT 1) locus is on…

Chromosome 19

Se gene (FUT 2) locus is on…

Secretor gene (Se or FUT 2)

Gene that leads to A and B Ags in gastrointestinal, genitourinary, and respiratory tract secretions, as well as in milk, sweat, tears, and amniotic fluid (NOT in CSF)

Glycoproteins; oligosaccharides

(Se) Secreted Ags are mostly (——), or mucins, but can also be free (——) in milk and urine

• Glycolipids

• Type 2

• Beta 1→4

• (FUT 1) by H gene

RBC Ags characteristics (Basic backbone, precursor chain, linkage, L-fucosyl-transferase)

• Glycoproteins

• Type 1

• Beta 1→3

• (FUT 2) by Se gene

Soluble substance characteristics (basic backbone, precursor chain, linkage, L-fucosyl-transferase)

• Bombay

• O_h

The hh genotype is called “____” (designated as “____”); no L-fucosyl-transferase produced, no H substance/ag, no A or B ag present on RBCs, Only precursor substance found on RBCs

• Anti-A

• Anti-B

• Anti-H

Bombay people have (—3—) as “naturally occurring” antibodies in their plasma, leading to agglutnation reactions to all ABO blood groups

A₁ (> A₂)

Which A subgroup is more potent and produced more of the enzyme ⍺-3-N-acetyl-galactos-aminyl-transferase

A₁ (> A₂)

Which A subgroup is more prevalent/dominant

A₂

What subgroup do group A infants present as before their ABH ag have fully developed?

1. Anti-A,B sera obtain/manufactured from O donor

2. Anti-H

3. Adsorption-elution tests with Anti-A

4. Saliva studies for A and H ags

5. Monoclonal Ab reagents (common bc of specificity)

Detection methods for weak A subgroups (5)

anti-B1

Unlike an A subgroup, the presence of an “——” does not exist

• Cis AB

• Gal-NAc and Gal

(——) is when A and B genes are “next to each other”; gene mutations identified resulting in single transferase capable of both (—2—).

• Purple - RBC and plasma (hematology)

• Red - serum and clot (chemistry)

• Pink - RBC and plasma (official BB)

Blood bank patient specimen tubes (3) and their contents

• K₂EDTA - dry, plastic tube

• K₃ EDTA - liquid, glass tube

Purple top contents (2)

Liquid K₃ causes dilution → undetection of low titer Ab

Why is the glass purple top not ideal for blood bank testing?

• Spin for 5 minutes

• Use serum for Ab detection/identification

• Use sloughed RBC for blood typing

Procedure for blood bank testing using red top tube (3)

A₁

Dolichos bifluorus lectin is associated with which Ag

H

Ulex europaeus lectin is associated withi which Ag

N

Vicia graminea lectin is associated with which Ag

M

Iberus amaara lectin is associated with which Ag

T

Arachis hypogae lectin is associated with which Ag

Differentiates polyagglutinaation

Glycine soja lectin is associated with which Ag

Tn

Salvia sclarea lectin is associated with which Ag

Differentiates polyagglutination

Salvia horminum lectin is associated with which Ag

• Carefully review package inserts

• Adhere to the package insert instruction for use

• Adhere to the manufacturer’s restrictions and precautions - know your reagent’s limitations

When using any BB reagents, you must strictly follow these guidelines (3)

Saline

IgM BB antisera is usually contained in a “____” media

• Potentiator

• Saline

IgG BB antisera is usually contained in a “____” to enhance reactivity to RBCs OR in a “____” to react at the AHG phase of testing (antiglobulin reagent)

IgA

There is no known (——) BB antisera reagent at this time

• Immune

• Multiple B-cell lines

• Mixture of antibodies to multiple epitopes

Polyclonal antisera is usually a result of an (——) response, produced by (——); it has broader specificity due to (——)

• Single B-cell

• directed at single epitope

• Identical

Monoclonal anitsera reagents are produced by (——) with more specificity due to (——); The antibody molecules within this reagent are (——)

• Unlimited production

• No human source (animal by hybridoma)

• IgM → direct agglutination in shorter time

• No contaminating Abs

• Standardized reagent

• Little to no variation between batches

Advantages of monoclonal antisera (6)

Red cell reagents

Reagent used with patient sera to identify patietn Abs that are present; used as “positive” and “negative” controls when usign a specific antisera reagent (is in reverse testing, check cell reagents, and Ab panel)

• group O

• IgG2

Anti-A,B reagent is known as “____” typing sera; contains anti A,B of (——) subclass (not routinely used for testing)

Subgroup or mixed field

Forward types in ABO testing typically give 4+ reactions, unless…

Forward type ABO testing

Performed to detect A or B Ags on RBC membrane

Reverse type ABO testing

Performed to detect circulated Abs to A, B, AB, or H

Children < 6 mo

Who should not receive reverse ABO testing

Isohemagglutinins

ABO antibodies are also known as…

• IgM

• IgM and IgG2

Primarily (——) antibodies are found in groups A and B individuals, but both (—2—) antibodies are found in group O individuals

Anti-A,B

A single cross-reacting IgG Ab unique to O types (is NOT a combination of different Abs)

5-10 yrs

By age (——) adult levels of Abs are generally reached

>65 yrs

At (——) age, may have decreased ABO titers due to aging and weakened immune system

• Enhanced by low temp

• Inhibited by soluble A/B Ag

• Inactivated by 2-ME or DTT

• Predominant in non-immunized A and B donors

Characteristics of IgM anti-A and anti-B antibodies that is not shared with IgG Abs

• Chimerism (blood transfusion, BM transplant, exchange transfusion, feto maternal bleeding)

• Newborn infants

• Elderly patients

• Hypogammaglobulinemia (leukemia, immunodegiciency)

Common causes for weak reacting or missing Ab discrepancies in testing (4)

• A or B subgroups

• Leukemia (excess B)

• Acquired B phenomenon (gram neg septicemia, intestinal obstruction, colon/rectal cancer)

Common causes for weak reacting or missing antigen discrepancies in blood typing (3)

• Elevated globulin level (multiple myeloma, Waldenstrom’s macroglobulinemia, plasma cell dyscrasiasis, Hodgkin lymphoma)

• Plasma expanders (dextran, polyvinyl pyrrolidone)

• Wharton’s jelly (in cord blood)

Common cause for protein/plasma abnormality leading to rouleaux formation (discrepancy in blood typing) (3)

• Exposure of hidden erythrocyte T antigen (polyagglutination)

• Cold/warm autoantibody (AIHA)

• Transfused foreign antigen

• Unexpected ABO iso-agglutninin and alloantibody

• Antibody other than anti-A and anti-B

• cis AB individuals

Miscellaneous causes for discrepancies in blood typing (6)