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IMHM > ahg > Flashcards

ahg Flashcards

1
Q

obtained
from immunized nonhuman species bind to human
globulins such as IgG or complement

A

antiglobulin test

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2
Q

AHG reagent contains

A

IgG and complement proteins

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3
Q

Important step in AHG testing

A

washing the RBC

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4
Q

Unwashed rbc may lead to

A

false negative result

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5
Q

Mechanism of AHG testing

A

detection of the unknown, unidentified or weakly reactive antibodies

detection of weak and
nonagglutinating Rh antibodies in serum.

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6
Q

principle of AHG testing

A

sensitization of RBC

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7
Q

Agglutination reaction of IgM

A

large aggregation, large
particles

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7
Q

two types of AHG testing

A

direct and indirect type of AHG

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8
Q

IgG antibodies are termed

A

non-agglutinating

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9
Q

In vitro sensitization of RBC: it is a two-stage
process/ two stage technique are referred to as

A

indirect antiglobulin test

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10
Q

In vivo sensitization of RBC: a one-stage
procedure which is referred as

A

direct antiglobulin tes

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11
Q

RBCs are sensitized with

A

IgG alloantibodies, IgG autoantibodies, complement components

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12
Q

Reacts with Fc Region of the Gamma heavy chain of
the IgG molecule

A

Polyspecific AHG

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13
Q

If positive with polyspecific AHG

A

use monospecific AHG
to determine which components reacts with the red cell

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14
Q

License monospecific AHG

A

Anti-IgG and Anti-C3b to C3d

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15
Q

involves injecting
human serum or purified globulin into laboratory
animals, such as rabbits.

A

classic method of AHG

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16
Q

Production of POLYSPECIFIC AHG may occur in two ways:

A
  • Polyclonal production:
  • Monoclonal production
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17
Q

are a mixture of antibodies
from different plasma cell clones

A

polyclonal antibodies

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18
Q

are produced by identical
plasma cells

A

monoclonal antibodies

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19
Q

Produced ex vivo using tissue-culture
techniques

A

monoclonal production / ab

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20
Q

Usually produced in live animals

A

polyclonal production

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21
Q

Monoclonal production also called as

A

hybridoma technology

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22
Q

usually prepared in rabbit

A

POLYCLONAL AHG PRODUCTION

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23
Q

Usually mice is used in monoclonal antibody production/
hybridoma technique

A

MONOCLONAL AHG PRODUCTION

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24
Q

produced by immunizing one colony of rabbits with human immunoglobulin (IgG) antigen and another colony with human C3 antigen.

A

Conventional polyspecific antiglobulin reagents

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25
Q

Both colonies of animals are hyperimmunized to produce antibodies

A

high-titer, high-avidity IgG antibodies

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26
Q

performed by reacting
dilutions of each antibody against cells sensitized with
different amounts of IgG

A

block titration for anti-IgG pools

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27
Q

excess IgG antibody may lead to

A

prozoning

28
Q

can be used to prepare monospecific antibody as well as
polyspecific antibody

A

MONOCLONAL AHG PRODUCTION

29
Q

discovered a technique
to produce antibody arising from a single B cell

A

George Kohler and Cesar Milstein

30
Q

Are screened for antibodies with the required
specificity and avidity

A

monoclonal antibody

31
Q

Useful in producing high-titer antibodies with well defined
specificities to IgG and to the fragments of C3.

A

MONOCLONAL AHG PRODUCTION

32
Q

After fusing of spleen cells and myeloma cells, we need to suspend it on a media complemented with

A

PEG

33
Q

After the fusion, the cells are placed now in a selective
culture media

A

HAT or hypoxanthine-aminopterin-thymidine medium

34
Q

Enzyme lacks in myeloma cells

A

HGPRT
Hypoxanthine-guanine phosphoribosyl transferase

35
Q

is prepared by a
production process
similar to that
described for
polyspecific AHG

A

monospecific AHG

36
Q

Clinical significance in DAT

A
  • Hemolytic disease of the newborn (HDN)
  • Hemolytic transfusion reaction (HTR)
  • Autoimmune and drug-induced AIHA.
37
Q

not a required test in routine pretransfusion
protocols

A

DAT

38
Q

Sensitization For DAT

A

at least 100 to 500 IgG
molecules per RBCs and 400 to 1100 molecules of C3d
per RBCs.

39
Q

does not require the incubation phase because
of the antigen-antibody complexes formed in vivo

A

DAT

40
Q

Interpreting the significance of a positive DAT requires

A

knowledge in patient’s diagnosis, drug therapy, recent transfusion history,

41
Q

performed to determine in-vitro sensitization of
RBCs and is used in the following situations

A

IAT

42
Q

Requires the incubation phase because of the antigenantibody complexes formed in vitro

A

IAT

43
Q

sensitization for IAT

A

there must be between 100 and 200 IgG or C3
molecules on the cell to obtain a positive reaction.

44
Q
  • Sensitization can be influenced by several factors:
A

o Ratio of serum to cells
o The use of enhancement medium
o Temperature
o Incubation time
o Washing of RBCs
o Addition of AHG reagent

45
Q

RATIO OF SERUM TO CELLS:

A

40:1 or 2 drops of serum and 1 drop of a 5
percent red cell suspension

46
Q

ration of Detecting weak antibodies

A

4 drops of serum with 1 drop of 3% RCS)

47
Q

incubation time for 22% bovine serum albumin

A

30 mins

48
Q

Works by reducing the zeta potential, it allows the RBC
to approach each other

A

Works by reducing the zeta potential, it allows the RBC
to approach each other

49
Q

Tend to lower the Zeta potential of that particular RBC,

A

LISS

50
Q

a water-soluble linear polymer and is used as an
additive to increase antibody uptake. Its action is to
remove water, thereby effectively concentrating
antibody.

A

PEG

51
Q

Temperature

A

optimum temp - 37 C

52
Q

saline with decreased pH due to long prolonged
storage periods

A

increase rate of antibody
elution during washing process.

53
Q

Why should AHG should be added immediately after washing

A

to minimize the chance of antibody eluting
from the cell and subsequently neutralizing the AHG
reagent.

54
Q

FALSE-POSITIVE RESULTS

A
  • Overcentrifugation and overreading
  • dirty glassware
  • cells with a positive DAT will yield a positive IAT
55
Q

FALSE-NEGATIVE RESULTS

A
  • Inadequate or improper washing of cells
  • Undercentrifuge or overcentrifuge
  • Serum:cell ratio are not ideal
  • Cell suspension either too weak or too heavy
  • Low pH of saline
  • Inadequate incubation conditions in the IAT
  • Poor reading technique
56
Q

MODIFIED AND AUTOMATED AHG TEST TECHNIQUES

A
  • Low Ionic Polybrene technique
  • Enzyme-Linked Antiglobulin Test
  • Gel Technique
  • Solid Phase technique
57
Q

An RBC suspension is added to a microtiter well and
washed with saline.

A

ENZYME-LINKED ANTIGLOBULIN

58
Q

A rouleaux-forming reagent is added to allow the
sensitized cells to approach each other to permit crosslinking by the attached antibody.

A

LOW IONIC POLYBRENE TECHNIQUE

59
Q

The patient’s serum or plasma is added to each well in
the screen cell set along with LISS.

A

SOLID PHASE TECHNIQUE

60
Q

added to
reverse the rouleaux; however, if agglutination is
present, it will remain.

A

high ionic strength solution

61
Q

In solid phase technique what needs to be added after washing

A

indicator cell

62
Q

If no sensitization occurred

A

indicator cells form a pellet in the bottom of the well.

63
Q

If sensitization occurred

A

forming a diffuse pattern in the well

64
Q

gel used in gel technique

A

dextran acrylamide gel

65
Q

Does not contain any specific
reagent and acts only by its property of
trapping agglutinates

A

Neutral

66
Q

use a specific reagent
incorporated into the gel and are useful for
antigen determination.

A

Specific gel tests

67
Q

a valuable application of the
gel test and may be used for the IAT or the
DAT

A

AHG test

68
Q

how much percentage pf LISS is needed

A

0.8%

IMHM (10 decks)

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