Precipitation and Agglutination Reactions

Question 1

Affinity

Answer 1

The initial force of attraction that exists between a single FAB site on an antibody molecule and a single epitope or determinant site on the corresponding antigen.
(Think of the “strength of attraction” as lust.)

Question 2

Avidity

Answer 2

Represents the overall strength of antigen-antibody binding and is the sum of the affinities of the all the individual antibody-antigen combining sites.
(Think of the “strength of bond” as marriage)

Question 3

Precipitation

Answer 3

Involves combining soluble antigen with soluble antibody to produce insoluble complexes that are visible.

Question 4

Agglutination

Answer 4

The process by which particulate antigens such as cells aggregate to form larger complexes when a specific antibody is present. `

Question 5

Zone of equivalence

Answer 5

Equal amounts of antigens and antibodies.

Question 6

Prozone phenomenon

Answer 6

A greater amount of antibodies than antigens.

Question 7

Postzone phenomenon

Answer 7

A greater amount of antigens than antibodies.

Question 8

Lattice

Answer 8

Formation of a stable network of antibodies and antigens.

Arrangement results in a multimolecular lattice that increase increases in size until it precipitates out of solution.

Question 9

Turbidimetry

Answer 9

A measure of the turbidity or cloudiness of a solution.

Question 10

Nephelometry

Answer 10

Measures the light that is scattered at a particular angle from the incident beam as it passes through a suspension

Question 11

Rate nephelometry

Answer 11

Measures serum proteins.

Question 12

RID stands for:

Answer 12

Radial immunodiffusion

Question 13

Radial immunodiffusion

Answer 13

A single-diffusion technique.
Antibody is uniformly distributed in the support gel and antigen is applied to a well cut into the gel. As the antigen diffuses out from the well, antigen-antibody combination occurs in changing proportions until the zone of equivalence is reached and a stable lattice network is formed in the gel. The area of the ring obtained is a measure of antigen concentration that can be compared with a standard curve obtained by using antigens of known concentration.

Question 14

Passive immunodiffusion

Answer 14

When no electrical current is used to speed up the process.
The rate of diffusion is affected by the size of the particles, the temperature, the gel viscosity, and the amount of hydration.

Question 15

End-point method

Answer 15

A technique for the measurement of radial immunodiffusion.
Antigen is allowed to diffuse to competition; when equivalence is reached, there is no further change in the ring diameter.