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Immunohematology > Lecture 6 > Flashcards

Lecture 6 Flashcards

1
Q

Antibody detection

A

key process in pretransfusion compatibility testing
ids in the detection and monitoring of patients who are at risks of delivering infants with hemolytic disease of the newborn (HDN) or hemolytic transfusion reactions (HTR) and immune hemolytic anemias

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2
Q

What is the focus on antibody detection?

A

“irregular” or “unexpected” antibodies as opposed to the “expected” antibodies of the ABO system

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3
Q

Immune alloantibodies

A

produced in response to RBC stimulation through: transfusion, transplantation, or pregnancy

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4
Q

Naturally occurring antibodies

A

produced without RBC stimulation
These antibodies may form because of exposure to environmental sources

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5
Q

Passively acquired antibody

A

produced in another individual and then transmitted to the patient through plasma-containing blood products or derivatives such as intravenous immunoglobulin (IVIG) transfusions.

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6
Q

What unexpected antibodies are great concern?

A

unexpected antibodies that cause decreased survival of the RBCs that possess the target antigens

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7
Q

clinically significant antibodies

A

usually IgG antibodies, react at 37C or AHG

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8
Q

Autoantibodies

A

antibodies that are directed at the individual’s own RBC antigens
React with all cells tested

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9
Q

Tube Technique

A

the traditional method of detecting antibodies is an indirect antiglobulin test (IAT) perform in a tube
2 drops patient’s serum or plasma is tested against 1 drop re-suspended O reagent RBCs with known antigens

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10
Q

What are steps to the IAT?

A

4:
Immediate spin
thermal enhancement
AHG
CC

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11
Q

IAT: IS phase

A

first phase of the test occurs in saline at room temperature
After centrifuging, the cell are examined for agglutination

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12
Q

Antibodies reacting below body temperature(37C) are?

A

considered cold antibodies
most cold antibodies are not clinically significant

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13
Q

IAT: Thermal phase

A

second phase of the test, requires incubation at 37C
Following incubation, the tubes are centrifuged and examined for agglutination

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14
Q

IAT: Antihuman globulin (AHG)

A

If thermal test is negative, proceed to AHG phase
Wash cells 3Xs and thoroughly pour off supernatant, Add AHG reagent, centrifuge, examine for agglutination

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15
Q

IAT: CC

A

If AHG Test is negative, Add check-cell
All negative tubes should be positive when tested with check-cell
verifies AHG reagent viability

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16
Q

RBC reagent

A

prepared from O cell individuals (anti-A and anti-B will not interfere in the detection of antibodies )
cells are suspended in 2%-5% concentrations of saline preservative (maintains the antigens and prevents hemolysis.)

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17
Q

How many sets are needed for screening cells

A

packaged in sets of two or three cells with varied antigen expression
Within the set, there should be one cell that is positive

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18
Q

Screening cell antigens

A

Rh: D,C,c,E,e,Cw
Kell: K, k,
Duffy: Fya, Fyb
Kidd: Jka, Jkb
Lewis: Lea, Leb
MN: M, N, S, s,
Lutheran: Lua, Lub

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19
Q

homozygous antigen expression

A

an individual who inherited only one allele at a given locus.
Therefore, the cell surface has a double dose of that antigen

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20
Q

heterozygous antigen expression

A

a person who inherited two different alleles at a locus
The alleles “share” the available antigen sites on the cellular surface

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21
Q

Which is stronger: Heterozygous or homozygous dosage

A

Homozygous expression gives a stronger reaction than heterozygous expression

22
Q

Zeta Potentional

A

increasing the dielectric constant the cells drift closer together enabling antibodies to attach and agglutinate the cells

23
Q

Other potentiators:

A

22% albumin
Low Ionic Strength Solution (LISS)
Polyethylene Glycol (PeG)

24
Q

Albumin

A

reduces the zeta potential by decreasing the differences in the ionic layers surrounding the red cells
an increase in the dielectric constant

25
LISS
lowers the zeta potential (increases the dielectric constant) and increases the uptake of antibodies onto the RBC
26
PeG
a LISS solution removes water from the test system - concentrating any antibodies present can cause nonspecific aggregation of cells more sensitive than LISS, albumin, or saline systems
27
AHG reagent
allows for the agglutination of incomplete antibodies contain anti-IgG
28
Polyspecific AHG
contains antibodies to both IgG and complement components C3, and C4 or C3b and C3d
29
Monospecific AHG
contains anti IgG only
30
Screening Cells
Agglutination or hemolysis at any stage of testing is a positive test result: indicating the need for antibody identification studies
31
Antibodies of the IgM class react
best at low temperatures and are capable of causing agglutination of the saline-suspended RBCs anti-N, anti-I, and anti-P1
32
Antibodies of IgG class react best
at the AHG phase Rh, Kell, Kidd, and Duffy
33
Autologous control
patient’s cells tested against the patient’s serum in the same manner as the antibody screen
34
Autologous control: Test results
positive antibody screen + negative autologous control= an alloantibody has been detected positive autologous control may indicate the presence of autoantibodies or antibodies to medications
35
More than one screening cell sample may be positive when
the patient has multiple antibodies when a single antibody’s target antigen is found on more than one screening cell or; when the patient’s serum contains an autoantibody
36
A single antibody specificity
suspected when all cells react at the same phase and strength
37
Multiple antibodies
most likely when cells react at different phases and strength
38
Rouleaux
characterized as stacked coins dispersed with the addition of 2 to 3 drops of saline to the test tube Serum from patients with: altered albumin-to-globulin ratios (Myeloma), high-molecular-weight plasma expanders
39
Limitations of Screening tests
Cell to serum ratio: antibody is present in excess, false negative reactions occur Length of Incubation: PH: Optimum pH between 6.8 and 7.2
40
Antibody Identification
Once an antibody has been detected, additional testing is required to identify the antibody(s) and to determine its clinical significance
41
Patient History
Information concerning the patient’s age, sex, race, diagnosis, transfusion history, pregnancy history, medications, and intravenous solutions may provide valuable clues in antibody identification studies, especially with complex cases
42
Antibody ID Panel
a collection of 11 to 20 group O cells with various antigen expression pattern of antigen expression should be diverse enough that it will be possible to distinguish one antibody from another and should include cells with homozygous expression
43
Exclusion/Rule-out Principle
first step is to exclude antibodies that could not be responsible for the reactivity seen cells that gave a negative reaction in all phases of testing are examined rule-out” technique only if the antigen is homozygously expressed on the cell
44
inclusion technique
remaining antigens should be examined to see if the pattern of reactivity matches a pattern of antigen-positive cells
45
DAT
used to detect in-vivo sensitization of RBCs
46
Elution
used to release, concentrate, and purify antibodies When IgG antibodies are detected, the next step is to dissociate them for identification
47
Absorption
In cases where the coating antibody resists elution RBCs to be phenotyped are incubated with diluted antiserum The supernatant is harvested and tested against a cell with heterozygous antigen expression
48
Absorption test results
if the patient’s cell is positive for the target antigen, the antibody will have been absorbed from the diluted antiserum If the patient’s cells are negative for the target antigen, the antibody will remain in the antiserum
49
Neutralization
In cases where the coating antibody resists elution Other substances in the body and in nature have antigenic structures similar to RBC antigens used to neutralize antibodies in serum, allowing for separation of antibodies or confirmation that a particular antibody is present
50
Autoadsorption
Autoantibodies are commonly removed through adsorption techniques The autologous cells are first washed thoroughly to remove unbound antibody They may then be treated to remove any autoantibody coating the cells

Immunohematology (16 decks)

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