Precipitation & Agglutination Reactions

Question 1

Define serology.

Answer 1

Study of fluid components in the blood, especially antibodies.

Question 2

Define serum.

Answer 2

Liquid portions of the blood without coagulation factors.

Question 3

Define antigen.

Answer 3

A foreign substance that initiates an immune response in the human body.

Question 4

Define antibody.

Answer 4

A protein produced in response to antigens.

Question 5

What are examples of antibodies?

Answer 5

Immunoglobulins.

Question 6

What is a monoclonal antibody?

Answer 6

An antibody that recognizes one epitope.

Question 7

What is a polyclonal antibody?

Answer 7

Recognizes multiple epitopes.

Question 8

Define sensitivity.

Answer 8

To correctly identify the patients WITH the given disease you are looking for.

Question 9

Define specificity.

Answer 9

To correctly identify the patients WITHOUT the given disease you are looking for.

Question 10

What types of tests do highly sensitive tests work well?

Answer 10

Screening testing.

Question 11

What types of tests do highly specific tests work well?

Answer 11

Confirmatory testing.

Question 12

What is a qualitative result?

Answer 12

The presence or absence of a particular antibody.

Question 13

What is a semi-quantitative test?

Answer 13

Provide an estimate of the quantity of a patient’s antibodies produced against infection.

Question 14

What is a quantitative result?

Answer 14

A specific amount of analyte.

Question 15

What is a precipitation assay?

Answer 15

Soluble antigen combines with soluble antibody which produces a visible, insoluble complex.

Question 16

What is an agglutination assay?

Answer 16

An antigen-antibody complex where antigen is bound to a particle or cell.

Question 17

What is a requirement for a precipitation reaction?

Answer 17

Antigen and antibody must have multiple binding sites for one another. Equal relative concentration of each.

Question 18

Define affinity.

Answer 18

Amount of initial attraction between antibody Fab site and antigen epitope.

Question 19

Define avidity.

Answer 19

Sum of all the attractive forces between antibody and antigen. The “strength” of the forces.

Question 20

Define the Law of mass action equation.

Answer 20

K = [AgAb]/[Ab][Ag]

Question 21

K, from the law of mass action, is dependent on what?

Answer 21

The strength of binding between the antibody and antigen.

Question 22

As K increases, the amount of AgAb complexes form. This causes the reaction to be ___.

Answer 22

more visible.

Question 23

Define prozone in the precipitation curve.

Answer 23

A large excess of antibody.

Question 24

Define postzone in the precipitation curve.

Answer 24

A large excess of antigen.

Question 25

How is the electric current effected with passive gel precipitation.

Answer 25

No electric current; slow movement of precipitants.

Question 26

How is the electric current effected with non-passive gel precipitation.

Answer 26

Electric current present; fast movement of precipitants.

Question 27

Describe nephelometry.

Answer 27

Light scattered at an angle and is measured indicating the amount of antigen or antibody present.

Question 28

In nephelometry, light scatter will ___ when the amount of immune complexes ___.

Answer 28

increase; increase.

Question 29

Describe turbidimetry.

Answer 29

Measures cloudiness; the reduction of light transmission causes greater absorbance.

Question 30

Describe radial immunodiffusion.

Answer 30

A single passive diffusion technique where gel is infused with antibody, and the patient antigen sample is added to wells. Measurement of radius determines antigen concentration.

Question 31

Describe ouchterlony double diffusion.

Answer 31

A double diffusion technique where antibody AND antigen diffuse from wells. Lines on the precipitation indicate antigen relationship.

Question 32

What are the three types of patterns with the ouchterlony double diffusion technique?

Answer 32

Identity, partial identity, and nonidentity.

Question 33

What type of ouchterlony double pattern is shown?

Answer 33

Identity / serological identity.

Question 34

What type of ouchterlony double pattern is shown?

Answer 34

Nonidentity.

Question 35

What type of ouchterlony double pattern is shown?

Answer 35

Partial identity.

Question 36

Describe immunofixation electrophoresis.

Answer 36

A double-diffusion (non-passive technique) that measures antibody isotope levels. Unknown antigens are electrophoresed then antibody (monoclonal) is applied to gel.

Question 37

In immunofixation electrophoresis, when do precipitates form?

Answer 37

When antigen-antibody combination forms.

Question 38

In immunofixation electrophoresis, the first lane detects what?

Answer 38

All serum proteins.

Question 39

List and describe the two steps of an agglutination reaction.

Answer 39

(1) Sensitization: initial binding. | 2) Lattice formation: formation of large aggregates (visible

Question 40

What are the two enhancement stains used for AbAg reactions?

Answer 40

LISS (low ionic strength saline) | PEG (polyethylene glycol)

Question 41

How does LISS effect reactions?

Answer 41

Neutralizes surface charge and cells can get closer together.

Question 42

How does PEG effect reactions?

Answer 42

Enhances viscosity and decreases water around cells which brings them closer together.

Question 43

Define AHG (antihuman globulin).

Answer 43

(Coombs reagent) Attaches to the Fc portion of IgG and helps to bridge the gap between RBCs so that a visible agglutination reaction can occur.

Question 44

Describe direct antiglobulin (DAT), Coombs test.

Answer 44

Antibodies are attached to cells inside the body and AHG is added to a patient's red cells to cause agglutination.

Question 45

Describe the indirect antiglobulin test (IAT).

Answer 45

Patient's antibodies are added to purchased RBCs. AHG is added to sensitize RBCs which causes agglutination.

Question 46

What are three enhancement factors in AgAb reactions?

Answer 46

(1) Temperature. (2) pH. (3) Type of antibody.

Question 47

Describe direct agglutination.

Answer 47

Antigen is naturally present on the cell or particle.

Question 48

Describe indirect (passive) agglutination.

Answer 48

An antigen that is artificially adsorbed to carrier particle or cell.

Question 49

Describe reverse passive agglutination.

Answer 49

ANTIBODY is attached to carrier particle or cell. This technique is used to detect if the antigen is present.

Question 50

Determine if this is passive or reverse passive agglutination.

Answer 50

Passive.

Question 51

Determine if this is passive or reverse passive agglutination.

Answer 51

Reverse passive agglutination.

Question 52

Describe agglutination inhibition.

Answer 52

Competition between particulate (purchased antigen) and soluble antigens (patient) for limited antibody-combining sites.

Question 53

In agglutination inhibition, when no agglutination occurs what is this indicative of?

Answer 53

A positive result.