MIDTERM LECTURE 3: DETECTION AND IDENTIFICATION OF ANTIBODIES Flashcards
significance of detection of antibodies directed against RBC antigens
1) investigates potential hemolytic transfusion reactions and immune hemolytic anemias
2) detect and monitor px who are at risk of delivering infants with HDFN
the detection methods are focused on what kind of antibodies
irregular or unexpected antibodies
what are the unexpected antibodies
1) immune alloantibodies
2) naturally occurring antibodies
3) passively acquired antibodies
4) autoantibodies
5) clinically significant alloantibodies
unexpected antibodies that are produced in response to RBC stimulation through transfusion, transplantation, or pregnancy
immune alloantibodies
unexpected antibodies that are formed as a result of exposure to environmental sources such as pollen, fungus, and bacteria
naturally occurring antibodies
T or F:
naturally occurring alloantibodies are produced without RBC stimulation
T
unexpected antibodies that are produced in one individual and then transmitted to another individual
passively acquired antibodies
how can passively acquired antibodies be transmitted
via
1) plasma-containing blood components
2) derivatives i.e. intravenous immunoglobulin (IVIG)
unexpected antibodies that are directed against antigens expressed on one’s own RBCs
autoantibodies
unexpected antibodies that cause decreased survival of RBCs possessing the target antigen
clinically significant alloantibodies
the presence of what kind of unexpected antibodies can complicate the detection of clinically significant alloantibodies
1) naturally occurring alloantibodies
2) passively acquired antibodies
3) autoantibodies
what immunoglobulin class are clinically significant alloantibodies
IgG
at what phase of IAT does clinically significant alloantibodies react
antihuman globulin (AHG) phase
performed to determine the specificity of the antibody present when an unexpected antibody is detected in the antibody screen
antibody identification panel
percentage of the population that has detectable RBC antibodies
0.2-2%
what requires the use of an antibody screen to detect clinically significant antibodies in allogeneic blood donors and in px as part of pretransfusion compatibility testing
Association for the Advancement of Blood & Biotherapies (AABB)’s Standard for Blood Banks and Transfusion Services
T or F:
antibody screen is an AABB requirement
F
why is antibody screen included in standard prenatal testing for obstetric patients
1) to evaluate risk of HDFN
2) assess the mother’s candidacy for Rh globulin (RhIg) prophylaxis
when can an antibody screen may additionally be performed
evaluating the compatibility of allogeneic HSC and bone marrow donors with the intended transplant recipient
traditional testing method used to detect clinically significant antibodies
IAT performed in a test tube
what are the reagents used to sensitize reagent RBCs with the patient’s antibodies
1) RBC reagents (suspended at 2-5% conc. in a preservative diluent)
2) enhancement reagent
3) AHG reagent
Antibody that reacts in immediate spin phase
cold reacting Ab (IgM)
Antibody that reacts in 37C incubation phase
warm reacting Ab (IgG)
Tube technique order of procedure
A.) 37C incubation phase
B.) Observe agglutination
C.) Observe hemolysis
D.) Grade the reaction
E.) Addition of Coomb’s control cells
F.) Washing phase (3x)
G.) AHG/Coomb’s serum phase
H.) Immediate spin phase
HACBFGED
H.) Immediate spin phase
A.) 37C incubation phase
C.) Observe hemolysis
B.) Observe agglutination
F.) Washing phase (3x)
G.) AHG/Coomb’s serum phase
E.) Addition of Coomb’s control cells
D.) Grade the reaction
Coombs control cels aka
check cells
T/F: All negative tests
will have Coombs’ control cells
T
Identify if homo/heterozygous:
From an individual who inherited only ONE
allele at a given locus
homozygous
Identify if homo/heterozygous:
”share” available antigen
heterozygous
Identify if homo/heterozygous:
Inherited TWO different allele at a locus
heterozygous
Identify if homo/heterozygous:
“double dose” of antigen
homozygous
What blood group system must be tested against homozygous
Kidd bgs
Tube technique RBC reagent is from an individual with what blood type
From Group O individual
Why is tube technique RBC reagent from a group O individual?
Since anti-A and anti-B will not interfere in the detection of antibodies to other blood
group systems
RBC reagent that reduces zeta potential
22% albumin
RBC reagent that increases the uptake of antibody into the RBC during the sensitization phase
Low ionic strength solution
LISS contains _____ in an albumin solute
glycine
LISS increases/decreases(?) the possibility of agglutination
increases
22% albumin increases/decreases(?) the chances of agglutination
increases
RBC reagent that can cause nonspecific aggregation of cells
polyethylene glycol (PEG)
What does 22% albumin do which allows RBCs to approach each other?
disperse charges
RBC reagent that removes water from the test system
polyethylene glycol (PEG)
PEG increases/decreases(?) the degree of RBC sensitization
increases
Among 22% albumin, LISS, and PEG, which is more sensitive?
PEG
In elevated levels of plasma protein, such as
in multiple myeloma, is PEG appropriate for use?
No
(it is not appropriate for use due to increased precipitation of proteins)
Polyspecific AHG is also called
polyvalent or broad
spectrum Coombs’ serum
What does Coombs control cells (Check Cells) prove? enumerate
- Adequate washing is performed
- AHG reagent was added
- Reagent was working properly
- FAILED (if so, repeat procedure)
polyspecific AHG reagent contains
anti-AHG and anti-C3d
monospecific AHG reagent contains
either anti-AHG or anti-C3d
advantages of AHG
- Flexibility of the test system,
- Commonly available laboratory equipment
- Relative low cost
disadvantages of AHG
- Instability of the reactions
- Subjective nature of grading
- Amount of hands-on time
- Failure of the washing phase to remove all unbound antibody
