Blood Bank Lecture Exam I

MLS 4130

Serum

the liquid remaining after blood clots that contains antibodies

Plasma

the liquid remaining after blood centrifugation that contains clotting factors

Unexpected antibody

any detectable antibody against an RBC antigen that is not ABO, can only be formed after exposure

Affinity

the binding strength of a single antibody and antigen

Avidity

the binding strength of all serum antibodies with their respective antigens

Valency

the number of binding sites on a single antibody

Fab region

the binding portion of an antibody

Prozone

excess of antibody, causes a false positive

Postzone

excess of antigen, causes a false negative

High titer low avidity (HTLA) reaction

Weak (1+) reaction for a highly diluted solutions due to weak bonds, not typically considered clinically significant unless masking clinically significant reactions

Centrifugation reduces the zeta potential, which is the negative-charge repulsion between the cells.

Why does centrifugation enhance agglutination?

6.5-7.5

Ideal pH for agglutination reactions

22ºC

Ideal spin phase temperature

37ºC

Ideal AHG phase temperature

IgG

Which antibody requires the use of potentiators to visualize reactions?

IgM

Which antibody reacts easily in saline without the use of potentiators?

Anti-IgG and anti-C3d

What is in polyspecific antihuman globulin?

Polyspecific AHG is used to begin the DAT in all people except infants (lack of production) because it contains both anti-IgG and anti-C3d. A positive on polyspecific AHG needs identification of if it is due to IgG or C3d.

When is a polyspecific AHG used versus a monospecific AHG?

Gamma heavy chain, infrequently the light chain

What is anti-IgG specific to?

For identification of a variety epitopes

When is polyclonal AHG more useful than monoclonal?

Warm

Does anti-IgG identify cold or warm agglutinins?

Cold

Does anti-complement identify cold or warm agglutinins?

It is an “indirect” way of detecting IgM due to its ability to bind complement.

Why is anti-complement used rather than anti-IgM?

False negative due to inability of reagent AHG to bind to the correct regions.

Does a lack of or poor quality washing cause a false positive or negative?

Check cells identify if negative results are due to the patient being negative for the respective factor OR if the reagents are bad. If the patient is negative for the factor and reagents are good, the check cells should cause agglutination.

What is the role of check cells?

1+

What would the anti-C3 or anti-IgG reaction look like in a acute or delayed hemolytic transfusion reaction?

Drug-induced immune hemolytic anemia, paroxysmal cold hemoglobinuria, cold agglutinin disease

Potential conditions for a positive anti-C3 with 2-4+ reaction

Acute or delayed hemolytic transfusion reaction, passively acquired antibody, ABO hemolytic disease of the fetus and newborn

Potential conditions for a postiive anti-IgG with a 1+ reaction

Rh or other hemolytic disease of the fetus and newborn, drug-induced immune hemolytic anemia, warm autoimmune hemolytic anemia

Potential conditions for a positive anti-IgG with a 2-4+ reaction

Drug-induced immune hemolytic anemia and warm autoimmune hemolytic anemia

Potential conditions for a positive anti-IgG and anti-C3 with a 2-4+ reaction

ABO, Hh, and Se

What are the three genes that affect ABO inheritance?

Type 1 chain

glycolipid with a beta 1-3 linkage, primarily found in secretions

Type 2 chain

glycolipid with a beta 1-4 linkage, primarily found on the RBC surface

H antigen

the precursor structure that A and B are built upon

alpha-2-L-fucosyl transferase

What does the H antigen elicit production of?

L-fucose

What does the H antigen cause the transfer of?

Type 2 chains

What kind of chain does L-fucose transfer to?

Type 1 chains

What chain does the secretor gene elicit the transfer of L-fucose to?

alpha-3-N-acetylgalactoseaminyl transferase

What does the A antigen elicit production of?

N-acetyl-D-galactoseamine (GalNAc)

What does the A antigen cause the transfer of?

a-3-D-galactosyl transferase

What does the B antigen elicit production of?

D-galactose (GAL)

What does the B antigen cause the transfer of?

Blood type A

What blood type does this image represent?

Blood type B

What blood type does this image represent?

Monoclonal IgM

In ABO blood typing, the reagents are predominantly composed of what?

Identifying donor types

What is anti-AB used for?

45%

What is the frequency of phenotype O in white people?

50%

What is the frequency of phenotype O in black people?

40%

What is the frequency of phenotype A in white people?

26%

What is the frequency of phenotype A in black people?

11%

What is the frequency of phenotype B in white people?

20%

What is the frequency of phenotype B in black people?

4%

What is the frequency of phenotype AB in white and black people?

Dolichos biflorus

lectin used for agglutination of A1

Bandeiraea simplicifolia

lectin used for agglutination of B

Ulex europaeus

lectin used for agglutination of H

O>A2>B>A2B>A1>A1B

What is the order of blood type strength of Ulex europaeus agglutination from strongest to weakest?

A1B due to having A1, A, and B antigens

Which blood type bears the least amount of H antigen on the cell?

A1 antigen

What antigen does A1 blood type have that A2 does not?

Bombay phenotype

the lack of H antigen due to inheritance of hh

O blood group

What blood group do Bombay and para-Bombay individuals belong to?

Group I discrepancy

The discrepancy of a weak or missing reactions on the reverse type due to low affinity/avidity or lack of antibodies

The mixture of patient cells with patient serum to test for autoagglutination

What is an auto-control?

Group I due to lack of antibodies, incubate the sample and retry with auto and O cell controls

An elderly woman presents with a forward type of O but does not react to A cells or B cells, what discrepancy is most likely and what should be done?

Group II discrepancy

The discrepancy of an unexpected reaction in the front type

Acquired B syndrome

GalNAc cleavage due to enteric bacteria deacetylase, creating a molecule more antigenically similar to GAL

Group III discrepancy

The discrepancy due to plasma abnormalities or excess protein

Washing six times and/or saline replacement

How should suspected group III discrepancies be resolved?

Group IV discrepancy

The discrepancy due to cold autoantibodies, unexpected alloantibodies, and/or unexpected ABO isoagglutinins

A1 and A

Most common ABO isoagglutinin

Washing, DAT, autocontrol, autoantibody screen

How should suspected group IV discrepancies be resolved?

Rhesus macaques

What monkey was the D antigen discovered in?

RhAG

What antigen must be present for the expression of RhD and/or RhCE?

85%

D antigen frequency in white people

70%

C antigen frequency in white people

80%

c antigen frequency in white people

30%

E antigen frequency in white people

98%

e antigen frequency in white people

Antigens are determined by 3 pairs of genes, each complex determines D/d, C/c, and E/e, and are inherited in a linked fashion as a haplotype.

What is postulated by the Fisher-Race theory?

Antigens are determined by two genes, one on each chromosome pair, that controls the expression of Rh and production of agglutinogens.

What is postulated by the Wiener theory?

Antigens are number 1-3 in order of discovery and are negative if they are recessive.

How does Rosenfield code the antigens?

Weak D

RBCs not immediately agglutinated by anti-D must be tested for what?

C in trans to D, partial D, and few antigen sites

What are the three mechanisms of weak D?

Rh_null

blood type defined as a lack of Rh antigen sites that causes stomatocytosis and hemolytic anemia

The Rh antigen is a non-glycosated protein that resides on transmembrane proteins. It is important for RBC structure.

Why does Rh_null cause hemolytic anemia?

Rh_mod

weakened expression of Rh and LW due to RHAG gene mutations

G

Genes that code for D and C also code for which antigen?

Anti-D and anti-C

Anti-G activity cannot be separated from what two antibodies?

C_w

rare variant Rh antigen that is caused by an amino acid change in the RhCe protein

f

What antigen is also expressed if a person is ce?

rh_i

What antigen is also expressed if a person is Ce?

D > c > E > C > e

What is the order of immunogenicity of the Rh group antigens?

Positive DAT, IAT, & antibody screens; unexplained fever; elevated bilirubin; low hemoglobin and haptoglobin

What are the clinical signs of a transfusion reaction?

IgG₁ and IgG₃

What kinds of IgG are the most common cause of a transfusion reaction?

Dosage effect

an increase in immunogenicity against homozygous individuals versus heterozygous individuals

Extravascular

Is a transfusion reaction primarily intravascular or extravascular hemolysis?

Anti-c

R1R1 people with anti-E most always also make what?

Anti-G

Anti-D serum may also contain what?

Anti-D

Anti-C is rare but usually accompanies what?

Anti-c

Anti-f typically accompanies what?