Antigen and Antibody Reactions (P)

Question 1

What is immunogenicity?

Answer 1

It is the property of substance (immunogens or Ags) to induce a detectable immune response

Question 2

What is antigen specificity?

Answer 2

It is the property of Ag molecule (or its part) to react w/ the specific Ab

Question 3

What is antigenicity?

Answer 3

It is given by a surface structure of immunogen (antigenic determinants)

Question 4

What is the principle of antigenicity?

Answer 4

The organism responds only to those that are foreign to him

Question 5

The # of antigenic determinants usually varies w/ what?

Answer 5

1) Size

2) Chemical complexity of macromolecule

Question 6

Provide an ex that is connected to the # of antigenic determinants w/c usually varies w/ the size and chemical complexity

Answer 6

1) Egg ovalbumin has a MW of 42,000

2) It has 5 antigenic determinants and thyroglobulin and it has MW 700,000

Question 7

*What are the characteristics (or chemical nature) of Ags?

Answer 7

1) Proteins
2) Polysaccharides
3) Lipopolysaccharides
4) Nucleoproteins
5) Glycoproteins
6) Steroid hormones
7) Bacterial cells, viruses
8) Synthetic polypeptides
9) Synthetic polymers

Question 8

What is the characteristic of Abs?

Answer 8

These are proteins w/ the property of sp combination w/ Ag (or 1 antigenic determinant) w/c elicited their formation

Question 9

Igs account for what percentage of the total plasma proteins?

Answer 9

*Approx 20%

Question 10

What is affinity?

Answer 10

1) It refers to the strength of binding bet a single antigenic determinant and an individual Ab combining site
2) It is the sum of the attractive and repulsive forces operating bet the antigenic determinant and the combining site

Question 11

What is avidity?

Answer 11

1) It is the measure of the overall strength of binding of an Ag w/ many antigenic determinants and multivalent Abs
2) It is more than the sum of the individual affinities

Question 12

Avidity is influenced by what factors?

Answer 12

1) The valence of the Ab

2) The valence of the Ag

Question 13

What is the principle of precipitation?

Answer 13

Soluble Ag + Ab (in proper proportions) -> visible ppt

Question 14

What is present in precipitation w/c occurs due to the Ag-Ab rxn?

Answer 14

Lattice formation

Question 15

What is the mechanism of action w/c results to the production of lattice formation?

Answer 15

The Ag binds w/ Fab sites of 2 Abs

Question 16

What are the exs of the methods employing the principle of precipitation?

Answer 16

1) Double diffusion (Ouchterlony)
2) Single diffusion (Radial immunodiffusion)
3) Immunoelectrophoresis
4) Immunofixation

Question 17

Where can ppt be observed in precipitation rxns?

Answer 17

In the zone of equivalence

Question 18

What is present in prozone?

Answer 18

*Ab excess (soluble immune complexes)

Question 19

Can ppt be formed in the prozone?

Answer 19

No

Question 20

What is zone of equivalence?

Answer 20

It is where the optimal ratio of Ag/Ab is present

Question 21

Can ppt be formed in the zone of equivalence?

Answer 21

Yes

Question 22

What is the characteristic of the ppt that can be formed in the zone of equivalence?

Answer 22

Insoluble ppt

Question 23

What is present in the post-zone (postzone)?

Answer 23

*Excess Ag (soluble immune complexes)