Transfusion Medicine Quiz 3

Where are A, B and H substances found?

In all body secretions

what percentage of the population are secretors

80%

Inhibition testing is used for…

Determining when ABO substances are present in the body

A, B, and H antigens on the RBC can be…

glycolipids, glycoproteins or glycosphingolipids

ABH antigens are synthesized on…

ONLY type 2 precursor chains

What enzyme is produced by H

FUT1

FUT1 acts on what chains

type 2

ABH soluble substances are made from

glycoproteins

ABH soluble substances are synthesized on

type 1 chains

what enzyme is produced by Se

FUT2

what type of chain does FUT2 act upon

type 1

if there is agglutination during the inhibition test, the patient is a…

Non secretor

if there is no agglutination during the inhibition test, the patient is…

a secretor

what blood group has the highest level of H substance

O

how many antigenic specificities does the Rh blood group have

61

what is the most critical Rh antigen

Rh-D

why is Rh the most critical antigen

it is the most immunogenic red cell antigen

protein structures produced by Rh genes are not chemically linked to

sugar groups (aka ABO antigens)

protein structures produced by Rh genes are chemically linked to

fatty acids in the lipid bilayer on the red cell

what Rh antigen is the most immunogenic and the most clinically significant

D

what is a mosaic antigen

An antigen that is complex and prone to mutation because of its protein structure.

what is a partial d antigen

an incomplete D antigen that is only partially expressed due to how the protein folded

what is the clinical significance of a partial D

patients can make an anti-D that targets an epitope that is foreign. This matters when the patient is the recipient of this blood.

If someone with a partial D is the donor, we treat them as…

Rh pos

If someone is the recipient of partial D blood, we treat them as…

Depends on situation. Usually treated as Rh neg. They must get Rh neg transfusions and prophylactic treatments during pregnancy as they can have an immune response against Rh pos

what is a weak D

inherited gene that codes for a weakened expression of the D antigen. Number of antigen sites for D is low

what does a weak D affect

the detection of D in vitro

what is genetic Del

super rare condition where the red cells have an extremely low number of D antigen sites

what population is Del common in

Asian

what is the positional effect

when Rh-D is inherited on opposite chromosomes, the D antigen sites can be hidden by some of the C antigen sites

what is another name for the positional effect

steric hindrance

what is the F antigen

when c and e are located on the same chromosome, resulting in a compound antigen

where is the F antigen found

on Dce or dce

what is the G antigen

a shared epitope site on D antigen and C antigen

what is the Cw antigen

less then 1% of the population has this, must have C antigen

what is Rh null

No expression of any Rh antigens, can only recieve Rh null blood and make amazing donors

How are Rh antibodies usually stimulated

immune

what isotype are Rh antibodies

IgG

most Rh antibodies…

Do not activate complement in the vascular system. instead they follow the pathway of opsinization

what is antigen dosage

phenomenon where red cells of a homogenous person possess more antigen sites per red cell then a heterozygous person.

what happens when dosage is present

antibodies have a higher reaction with a homozygous cell then a heterozygous cell

what Rh antigen does not show dosage

D, as there is no d antigen

What is fisher-race inheritance theory

States that each parent will give you 3 genes

what is weiner inheritance theory

Each parent contributes one gene

in wiener shorthand, R means that

D is present

in weiner shorthand, r means that

D is absent (d)

In weiner shorthand, 1 and ‘ mean

C is present

In weiner shorthand, 2 and “ mean

E is present

in weiner shorthand, 0 means

ce is present

In weiner shorthand, Z paired with R means that

CE is present

in weiner shorthand, Y paired with r means that

CE is present

What is rosenfield inheritance theory

It is not genetic based, and indicates the absence or presence of an antigen using positive and negative symbols

what is ISBT

a universal language used to label blood donor bags. a system of numbers that indicates what antigens are present in the blood

what is tippett inheritance theory

The most accurate representation. states that:

We have 2 Rh genes on chromosome 1

One is RHD - codes for D

One is RHCE - codes for C,c,E,e

what is RHAG gene

Found on chromosome 6, must be inherited in order for Rh to be expressed. IF it is not, patient is Rh null

INHERITANCE TRUMPS…

MPG

ABO antibodies are

naturally occuring and expected

ABO antibodies are primarily…

IgM in isotype

Agglutination of IgM antibodies happens at

room temperature

IgM antibodies have a ____________ thermal range

large

IgM antibodies ________ complete lattice formation

easily

IgG ABO antibodies react at

37 degrees C AND need help to form the lattice structure, they are unable to overcome zeta potential independently

what is an adjuvant

something that enhances the body’s immune response

c3d is…

An adjuvant that can be used as a marker to detect cells that are marked for destruction

how does sensitization and agglutination work for an IgM antibody

sensitization and agglutination occur very quickly at room temperature and they do not need help overcoming zeta potential

how does sensitization and agglutination work for an IgG antibody

sensitization occurs at body temperature. a potentiator (LISS,PEG,Albumin or enzymes) can be added to aid in overcoming of zeta potential.

What is a monoclonal AHG reagent

a single clone of an antibody which shows a paratope that is specific for a single target. grown from a single cell line

what is a polyclonal AHG reagent

multiple clones of antibodies that are specific for a specific antigen. May target multiple epitopes on the antigen. grown from many cell lines

what is a poly specific AHG reagent

a single reagent that shows specificity against multiple specific antigens

what is a monospecific AHG reagent

a single reagent that shows specificity to a single antigen.

Most reagents are

monospecific

what is the DAT test?

A measure of sensitization that already happened in the patient. Detects antibodies or complement binding on the surface of the red cells.

a positive reaction on the DAT test indicates:

the patients red cells are coated with anti-IgG, anti-c3d or BOTH

if you do the DAT test, add check cells and the result it STILL negative, this means

the test results are invalid, as this MUST be a positive result

a negative result on the DAT test indicates that

the patients cells are not coated with anti-IgG or anti-c3d

what are check cells

cells with IgG antibodies pre bound to the red cell membrane

why are check cells used

to ensure available AHG reagent was not neutralized by improper cell washing

what happens if neutralization did occur from improper cell washing

the check cells will always bind more easily to AHG then the immunoglobulins that are bound to the red cell membrane

when is the DAT useful/needed?

• Delayed hemolytic transfusion reactions

• Delayed serological transfusion reactions

• Hemolytic transfusion reactions

• Hemolytic disease of the fetus and newborn

• auto immune hemolytic anemia

what is the difference between the DAT and the IAT

instead of using patient red cells we use plasma as it contains antibodies with unknown specificity

What is the IAT

detects antibodies in the patients plasma that could react with their red cells and cause hemolysis

when is the IAT useful/needed

• pre transfusion compatibility testing

• identification of allo antibodies

• Antibody titration

what is a complete antibody

an antibody that can agglutinate red cells in a saline solution (typically an IgM antibody) 

what is an incomplete antibody

an antibody that can only sensitize red cells in saline, not agglutinate (usually IgG antibody) 

what is cold agglutination

an antibody that reacts best in the cold (4 degrees C) and does not react at 37 degrees C unless it has a broad thermal range

what is warm agglutination

an antibody that reacts best at body temperature (37 degrees C) 

what is a naturally occurring antibody

an antibody that is produced in response to an unknown stimulus. This is usually due to ingestion of a substance present in nature that resembles blood group antigens. 

what is an immune antibody

An antibody produced in response to a known foreign stimulus being introduced into circulation 

what is a regular/expected antibody

an antibody present in the serum of all persons lacking the corresponding antigen (Anti-A, Anti-B, Anti-AB) 

what is an irregular/unexpected antibody

an antibody usually not present in the serum. Most blood group antibodies found in humans are irregular