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IMMUNOSEROLOGY > Labelled immunoassays > Flashcards

Labelled immunoassays Flashcards

1
Q

Purpose of labelled immunoassays.

A

Detects antigens or antibodies in small sizes or low concentrations.

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2
Q

Key mechanism of competitive labelled immunoassays.

A

Labeled antigen competes with patient antigen; result inversely proportional to analyte concentration.

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3
Q

Key mechanism of noncompetitive labelled immunoassays.

A

Capture antibody binds patient antigen; result directly proportional to analyte concentration.

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4
Q

Characteristic of heterogeneous immunoassays.

A

Requires washing step to separate bound from free analyte.

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5
Q

Characteristic of homogeneous immunoassays.

A

No separation step required; simpler but less sensitive.

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6
Q

Major disadvantage of heterogeneous immunoassays.

A

Complexity and high cost.

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7
Q

Discovery of radioimmunoassay (RIA).

A

Developed by Yalow and Berson in the 1950s.

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8
Q

Primary label used in RIA.

A

Radioactive isotopes.

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9
Q

Common isotopes in RIA.

A

Iodine-131, Iodine-125, Hydrogen-3, Carbon-14.

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10
Q

Device for measuring radioactivity in RIA.

A

Scintillation counter.

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11
Q

Analyte concentration relationship in competitive RIA.

A

Radioactivity inversely proportional to analyte concentration.

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12
Q

Analyte concentration relationship in noncompetitive RIA.

A

Radioactivity directly proportional to analyte concentration.

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13
Q

RIA clinical utility.

A

Highly sensitive for detecting drugs or hormones.

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14
Q

Health risks of RIA.

A

Radioactive exposure, potential mutagenesis, and carcinogenicity.

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15
Q

Discovery of fluorescent immunoassay.

A

Albert Coons, 1941.

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16
Q

Key label in fluorescent immunoassay.

A

Fluorophores or fluorochromes.

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17
Q

Outcome of a positive fluorescent immunoassay.

A

Fluorescent light emission proportional to antigen/antibody concentration.

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18
Q

Most commonly used fluorophore.

A

FITC (Fluorescein Isothiocyanate), emits green light.

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19
Q

Fluorophores emitting red light.

A

Phycocyanin, Texas Red.

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20
Q

Fluorophore emitting red-orange light.

A

Tetramethyl rhodamine.

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21
Q

End result of a fluorescent immunoassay.

A

Emission of fluorescent light.

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22
Q

Target and labeled reagent in direct immunofluorescent assay.

A

Target: Antigen; Labeled reagent: Antibody.

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23
Q

Applications of direct fluorescent immunoassays.

A

Diagnosis of viral diseases (HSV, CMV, EBV), detection of cell surface antigens, Chlamydial antigens, and in flow cytometry.

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24
Q

Target and labeled reagent in indirect immunofluorescent assay.

A

Target: Antibody; Labeled reagent: Antihuman-globulin (AHG).

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25
Q

Applications of indirect immunofluorescent assays.

A

FTA-ABS, FANA testing.

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26
Q

Principle of fluorescence polarization immunoassay (FPIA).

A

Based on the change in polarization of fluorescent light emitted from a labeled molecule when bound by an antibody.

27
Q

Relationship between fluorescence polarization and analyte concentration in FPIA.

A

Inversely proportional to analyte concentration.

28
Q

Instrument used in fluorescence polarization immunoassay.

A

Polarization analyzer.

29
Q

Advantage of fluorescence polarization immunoassay.

A

More sensitive and specific.

30
Q

Disadvantage of fluorescence polarization immunoassay.

A

Quenching decreases the intensity of fluorescence.

31
Q

Label used in enzyme immunoassay (EIA).

A

Enzymes.

32
Q

Common substrates used in enzyme immunoassays (EIA).

A

HPO, ALP, and Glucose oxidase

33
Q

Commonly used enzyme in enzyme immunoassays (EIA).

A

ALP (Alkaline Phosphate), prepared from calf intestine; Horseradish Peroxidase from horseradish

34
Q

Enzyme used in enzyme immunoassays (EIA) that catalyzes glucose oxidation.

A

Glucose oxidase.

35
Q

Enzyme used in enzyme immunoassays (EIA) for breaking down lactose.

A

B-galactosidase.

36
Q

Types of breakdown products in enzyme immunoassays (EIA).

A

Chromogenic, fluorogenic, or luminescent products are produced.

37
Q

End reaction of enzyme immunoassay (EIA).

A

Colorimetric reaction with chromogenic substrate.

38
Q

Principle of enzyme immunoassay (EIA).

A

Absorbance of -the colored end product is directly proportional to enzyme activity.

39
Q

Competitive enzyme immunoassay (EIA) mechanism.

A

Labeled antigen competes with unlabeled patient antigen for binding sites on antibody molecules.

40
Q

Relationship between enzyme activity and analyte concentration in competitive enzyme immunoassay (EIA).

A

Enzyme activity is inversely proportional to analyte concentration.

41
Q

Applications of competitive enzyme immunoassay (EIA).

A

Used for measuring small, pure antigens such as drugs and hormones.

42
Q

Mechanism of non-competitive enzyme immunoassay (EIA).

A

Solid phase antigen, antibody (sample), enzyme-labeled anti-Ig, and substrate are used to measure antibody concentration.

43
Q

Measurement in non-competitive enzyme immunoassay (EIA).

A

The amount of color, fluorescence, or luminescence is directly proportional to antibody concentration.

44
Q

Solid-phase support used in non-competitive enzyme immunoassay (EIA).

A

Microtiter plates, nitrocellulose membranes, magnetic, or latex plastic beads.

45
Q

Applications of non-competitive enzyme immunoassay (EIA).

A

Used for measuring antibody production against infectious agents and for autoantibody testing.

46
Q

Technique that uses two antibodies, one attached to a solid phase and the other as a label to capture a specific antigen.

A

Sandwich/Double Ab/Antigen capture technique (Heterogeneous assay).

47
Q

Type of assay used in ELISA where an antibody is attached to a solid phase, serum with target antigen is added, and labeled AHG is used.

A

Double Antibody Technique (Sandwich ELISA).

48
Q

Type of assay in ELISA that is homogeneous, simple to perform, and used for determining low-molecular-weight analytes.

A

EMIT (Enzyme Multiplied Immunoassay Technique).

49
Q

Advantages of ELISA, especially in terms of cost and automation.

A

Cheap, long shelf life, easily adapted to automation, sensitive with inexpensive equipment.

50
Q

Disadvantages of ELISA related to natural inhibitors and protein binding.

A

Natural inhibitors, size of enzyme label, nonspecific protein binding.

51
Q

Immunoassay performed in a plastic cartridge with a membrane that enhances speed and sensitivity of ELISA reactions.

A

Rapid Immunoassays.

52
Q

Technique where antigen or antibody migrates through a strip and forms a colored line at the detection zone in the presence of the target.

A

Immunochromatography.

53
Q

Type of immunoassay that involves emission of light caused by a chemical reaction with reagents like luminol or acridinium esters.

A

Chemiluminescent Immunoassay.

54
Q

Immunoassay that uses chemiluminescent molecules to emit light energy as labels.

A

Chemiluminescent Immunoassay (CLIA).

55
Q

Examples of chemiluminescent molecules used in CLIA.

A

Luminol, Acridinium phosphate ester.

56
Q

Advantage of chemiluminescent immunoassay due to its light emission detection and stable reagents.

A

Excellent sensitivity, stable reagents, inexpensive, faster turnaround time.

57
Q

Type of assay where enzyme activity is inhibited by preventing interaction with the chromogenic substrate.

A

Enzyme Inhibition.

58
Q

Type of indirect ELISA where antigen is attached to a well, and patient serum is tested for antibodies.

A

Indirect ELISA.

59
Q

Result of colorimetric reaction in indirect ELISA when enzyme-linked antibody binds to antigen.

A

Color indicates the presence of antibody, directly proportional to antigen-antibody reaction.

60
Q

Immunoassay that uses colloidal particles like gold or silver as labels.

A

Sol Particle Immunoassay.

61
Q

Most commonly used colloidal particle in sol particle immunoassay due to its characteristic magenta-colored product.

A

Gold.

62
Q

Colloidal particle used in sol particle immunoassay when gold is too expensive.

A

Silver.

63
Q

Type of sol particle immunoassay where one type of particle is used as the label.

A

Homogeneous Sol Particle Immunoassay.

64
Q

Type of sol particle immunoassay that uses a mixture of particles and requires separation prior to measurement.

A

Heterogeneous Sol Particle Immunoassay.

IMMUNOSEROLOGY (22 decks)

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