ABO Blood Group System (ASCPi)

ABO (ISBT 001)

• It is the ONLY blood group system in which individuals have antibodies in their serum to antigens that are ABSENT from their RBCs

• Causes the most severe HTR

Long arms of Chromosome 9

The three genes that code for A, B, O are located at the:

37th day of fetal life

ABO antigens are developed at:

2-4 years of age

Full expression of ABO antigens occur between:

H gene

FUT1, located in chromosome 19

Se gene

FUT2, located in chromosome 19; codes for the production of α-2-Lfucosyltransferase

• Saliva

• Tears

• Milk

• Digestive juices

• Bile

• Urine

• Amniotic fluid

• Pathologic fluids

Fluids in which ABH substances can be detected:

Plasma

Origin of Type 1 precursor chain

Erythrocytic precursors

Origin of Type 2 precursor chain

H, A, B, Se, and Lewis

Controlling genes of Type 1 precursor chain

H, A, and B

Controlling genes of Type 2 precursor chain

ABO antibodies

Naturally occurring and predominantly IgM in nature

3-6 months of age

ABO antibodies are pre-formed and developed between:

5 – 10 years of age

ABO antibodies peak between:

Direct / Forward typing

Uses known sources of antisera TO DETECT ANTIGENS of an individual’s red cells

Clear blue

What is the color of Anti-A reagent?

Clear yellow

What is the color of Anti-B reagent?

Ulex europaeus

Lectin for Anti-H

Dolichus biflorus

Lectin for Anti-A

Griffonia simplicifolia (Bandeiraea

simplicifolia)

Lectin for Anti-B

• Arachis hypogaea (Anti-K, Anti-Tk)

• Glycine soja (Anti-T, Anti-Tn, Anti-Cad)

• Salvia sclarea (Anti-Tn)

• Salvia horminum (Anti-Tn, Anti-Cad)

Lectins for antigens causing polyagglutination:

• Iberis amara (Anti-M)

• Vicia graminea and Bauhinia species (Anti-N)

Lectins for other blood group antigens:

Reverse / Indirect typing

Uses known A1 and B antigens and testing the serum of the patients FOR DETECTING AB

2-5%

Percent of red cell suspension used in reverse/indirect typing?

h/h

The genotype of the Bombay (Oh) phenotype is:

A3

Which phenotype has a mixed field agglutination with anti-A and/or anti-A,B

Aebd

Phenotype in which ≤10% red cells show very weak mf agglutination

Am

Phenotype in which secretors demonstrate quantities of A substance in saliva

Ay

Phenotype in which secretors contains small amount of A substance in saliva

Ael

Phenotype in which secretors contains only H substance and no A substance in saliva

Draw new sample

Which should be done if discrepancy persists?

• Incorrect or inadequate identification

  of blood specimens, test

  tubes, or slides

• Cell suspension either too heavy or too

  light

• Clerical errors or incorrect recording of

  results

• A mix-up in samples

• Missed observation of hemolysis

• Failure to add reagents

• Failure to add sample

• Failure to follow manufacturer’s

  instructions

• Uncalibrated centrifuge

• Overcentrifugation or

  undercentrifugation

• Contaminated reagents

• Warming during centrifugation

Common sources of technical errors resulting in discrepancies:

• Newborns

• Elderly patients

• Patients with a leukemia (e.g., chronic lymphocytic leukemia) or lymphoma (e.g., malignant lymphoma)

• Patients using immunosuppressive drugs

• Patients with congenital or acquired agammaglobulinemia or immunodeficiency diseases

• Patients with bone marrow or stem cell transplantations

• Plasma transfusion or exchange transfusion

• ABO subgroups

Group I discrepancies

• Obtaining the patient’s history

• Incubate the patient serum with reagent A1 and B cells at RT for approximately 15 to 30 mins

• Incubate at 4°C for 15 minutes (if still no reaction after centrifugation)

Resolutions for Group I Discrepancies:

• Subgroups of A (or B)

• Leukemias

• Hodgkin’s disease

• “Acquired B” phenomenon

Group II discrepancies

• Use 2-5% RCS

• Incubate the patient serum with reagent A1 and B cells at room temperature for approximately 15 to 30 mins or by adding one or two drops more plasma or serum to the test

• Incubated at 4°C for 15 minutes (if still no reaction after centrifugation)

• Use enzyme treated RBCs

Resolutions for Group II Discrepancies:

Protein or plasma abnormalities resulting in rouleaux formation

Group III discrepancies are described as:

• Elevated levels of globulin from certain disease (Waldenstrom’s, Multiple myeloma)

• Elevated levels of fibrinogen

• Plasma expanders

• Wharton’s Jelly

Group III discrepancies

Wash RBCs with saline at least 6-8 times

Resolution for Group III discrepancies

Acquired B phenomenon

It occurs when bacterial enzyme modifies immunodominant sugar A (N-acetyl-D-galactosamine) into D-galactosamine which cross reacts with anti-B antisera

• Use monoclonal anti-B clone (ES4)

• Treat RBCs using acetic anhydride

What is/are the resolution/s for Acquired B phenomenon?

• Polyagglutination

• Cold reactive antibodies

• Unexpected ABO isoagglutinins

• Antibodies other than anti-A and anti-B may react to from antigen-antibody complexes that may then adsorb into patient’s red cell

• RBCs with the cis “AB phenotype”

Group IV discrepancies

• RBC (sample) = wash with saline (37 degrees Celsius); 0.01 M Dithiothreitol (DTT)

• Serum (sample) = warm at 37 degrees Celsius the read results at 37 degrees Celsius

Resolutions for Group IV discrepancies