5. Blood Bank: Introduction to Blood Group Systems and the Lewis System

Comprehensive practice flashcards reviewing blood group systems notation, zygosity, grading, and the biochemistry, genetics, and serology of the Lewis blood group system.

According to the lecture, which rarer blood group antigens were mentioned as appearing below the red box?

Mucolten, SID, and SuprSID.

What abbreviation represents the Duffy blood group system antigens?

FY (such as FYA and FYB).

What abbreviation represents the Kidd blood group system antigens?

JK (such as JKA and JKB).

In the lecture notes, what temperature or antibody class is represented by a snowflake symbol?

Room temperature or colder, representing IgM antibodies.

What definition of a blood group system was historically asked on the certification examination?

A whole set of related chemical determinants that are found on an antigen.

What are the three ways antibodies are classified in the blood bank?

Clinically significant, insignificant, or naturally occurring.

At what temperature do clinically significant immune antibodies react?

$37^\circ\text{C}$ (or $37\text{ degrees}$).

Immune antibodies primarily belong to which immunoglobulin class?

IgG.

Approximately how many blood group systems and antigens are recognized according to the instructor?

Approximately $36$ to $39$ blood group systems and almost $350$ antigens.

What term describes pairs of antigens that are alternate alleles, such as FYA and FYB or JKA and JKB?

Antithetical partners.

In formal blood banking notation, how do subscripts and superscripts differ when denoting blood group expressions like $A_1$ and $A^1$?

A subscript denotes the phenotype, whereas a superscript denotes the allele.

How should a negative reaction be recorded on an antibody screen, rather than using dashes?

As a zero ($0$).

What range of scores is standard for grading the strength of positive agglutination reactions?

$1+$ to $4+$.

What does a typing result written as $[\text{Jk}(a+, b+)]$ indicate regarding gene inheritance?

It indicates heterozygosity, meaning the individual inherited an allele from each parent.

Why must a medical laboratory technologist specify 'anti-Kell' rather than simply stating 'Kell'?

To clearly specify whether they are referring to the Kell antibody or the Kell antigen.

Where are Lewis antigens synthesized before they reach red blood cells?

They are made by tissues and secreted into body fluids, then adsorbed onto the red cells from the plasma.

On which other blood cells besides erythrocytes are Lewis antigens found?

Platelets and lymphocytes.

If a prenatal tube testing sample emerges from the $37^\circ\text{C}$ water bath showing gross or marked hemolysis, what antibody system should be suspected?

Lewis.

Which specific gene encodes the Lewis transferase?

The FUT3 gene.

Which specific gene encodes the Secretor transferase?

The FUT2 gene.

Which specific gene encodes the H transferase?

The FUT1 gene.

What chemical class describes soluble Lewis and ABH antigens bound in plasma?

Glycosphingolipids.

What Lewis substance will always be present in secretions if an individual inherits the dominant Lewis ($Le$) gene?

Lewis a ($\text{Le}^a$).

What happens when an individual inherits both the dominant Lewis ($Le$) gene and the Secretor ($Se$) gene?

The H substance is converted to Lewis b ($\text{Le}^b$), which then preferentially adsorbs onto the red cells.

What secretions and red cell antigens are detected in an individual who inherits the amorph Lewis genotype ($lele$) but possesses the Secretor ($Se$) gene?

They secrete A, B, and H substances according to their ABO type, but have no Lewis antigens in secretions or on their red blood cells.

What will be detected in the body fluids and on the red cells of a person who has the dominant $Le$ gene but is a non-secretor ($sese$)?

They will have Lewis a ($\text{Le}^a$) in fluids and on red cells, but no soluble A, B, or H substances.

Why is there a reduced amount of Lewis b substance in the saliva of a group AB individual?

Because most of the precursor H substance has been utilized to build the A and B antigens, leaving less H available for conversion into Lewis b.

Between Lewis a and Lewis b, which is synthesized first, and which is preferentially adsorbed onto red blood cells?

Lewis a ($\text{Le}^a$) is synthesized first, but Lewis b ($\text{Le}^b$) is preferentially adsorbed onto red blood cells.

What is the most common Lewis phenotype in both Caucasian and African populations?

$\text{Le}(a-b+)$.

Which Lewis phenotype is considered rare in both Caucasian and African populations?

$\text{Le}(a+b+)$.

What is the typical Lewis phenotype of a newborn infant at birth?

$\text{Le}(a-b-)$.

At approximately what age do children reach their final adult Lewis antigen status?

Around $6$ or $7$ years of age.

Why are Lewis antibodies not implicated in Hemolytic Disease of the Fetus and Newborn (HDFN)?

They are predominantly IgM (cannot cross the placenta), and Lewis antigens are poorly developed on fetal and neonatal red blood cells.

Why is Lewis antigen expression described as 'transient' during pregnancy?

Maternal red cell Lewis antigens diminish or disappear during pregnancy (often temporarily typing as $\text{Le}(a-b-)$) due to altered lipoprotein concentration and hemodilution.

How long after delivery does it typically take for a mother's Lewis phenotype to return to normal?

It occurs gradually, taking anywhere from $6\text{ weeks}$ to $6\text{ months}$.

In individuals of which red cell phenotype do Lewis antibodies almost exclusively occur?

Individuals who phenotype as $\text{Le}(a-b-)$.

In which ABO blood group are Lewis antibodies most commonly formed?

Group O.

Why must tube agglutination tests for Lewis antibodies be resuspended very gently?

Agglutination by Lewis antibodies is extremely fragile and easily dissipates if shaken aggressively.

How can Lewis antibodies be neutralized in patient plasma to confirm or rule out other underlying antibodies?

By performing neutralization/inhibition testing using commercially prepared soluble Lewis substance.

When screening cells react with different strengths in an antibody screen, what are the first two diagnostic possibilities to consider?

Multiple antibodies present in the plasma or a single antibody demonstrating dosage.

Why is it unnecessary to screen for Lewis-negative donor blood units for a patient with a Lewis antibody?

Donor plasma contains soluble Lewis substances that neutralize the recipient's antibody, and donor Lewis antigens readily elute off transfused red cells.

Can an individual who phenotypes as $\text{Le}(a-b+)$ make an anti-Lewis a antibody?

No, because they still produce Lewis a in their body secretions.

Approximately what percentage of $\text{Le}(a-b-)$ individuals develop an anti-Lewis a antibody?

About $20\%$.

Under what circumstance can a Lewis antibody become clinically significant and cause a Hemolytic Transfusion Reaction (HTR)?

When it has an IgG component that is reactive at $37^\circ\text{C}$.

How does enzyme treatment of reagent red blood cells affect the reactivity of Lewis antibodies?

Enzymes enhance the reactivity of Lewis antibodies.

Under what clinical transfusion scenario can a patient potentially develop a Lewis antibody due to high exposure?

During a massive transfusion protocol ($10$, $20$, or $30$ units of blood).

Between anti-Lewis a and anti-Lewis b, which antibody occurs more commonly?

Anti-Lewis a ($\text{anti-Le}^a$).

With which cells does the subgroup antibody anti-Lewis bH ($\text{anti-Le}^{bH}$) react?

It reacts with cells that are $\text{Le}(b+)$ from individuals who are group $A_2$ or group O.

How does the reactivity of anti-Lewis bL ($\text{anti-Le}^{bL}$) differ from anti-Lewis bH?

Anti-Lewis bL reacts with $\text{Le}(b+)$ cells of any ABO blood group.

What soluble substances are present in the body fluids of an individual with the genotype $A/A$, $Le/le$, and $Se/se$?

A substance, H substance, Lewis a ($\text{Le}^a$), and Lewis b ($\text{Le}^b$).