Antigen and Antibody Reactions (P) Flashcards
What is immunogenicity?
It is the property of substance (immunogens or Ags) to induce a detectable immune response
What is antigen specificity?
It is the property of Ag molecule (or its part) to react w/ the specific Ab
What is antigenicity?
It is given by a surface structure of immunogen (antigenic determinants)
What is the principle of antigenicity?
The organism responds only to those that are foreign to him
The # of antigenic determinants usually varies w/ what?
1) Size
2) Chemical complexity of macromolecule
Provide an ex that is connected to the # of antigenic determinants w/c usually varies w/ the size and chemical complexity
1) Egg ovalbumin has a MW of 42,000
2) It has 5 antigenic determinants and thyroglobulin and it has MW 700,000
*What are the characteristics (or chemical nature) of Ags?
1) Proteins
2) Polysaccharides
3) Lipopolysaccharides
4) Nucleoproteins
5) Glycoproteins
6) Steroid hormones
7) Bacterial cells, viruses
8) Synthetic polypeptides
9) Synthetic polymers
What is the characteristic of Abs?
These are proteins w/ the property of sp combination w/ Ag (or 1 antigenic determinant) w/c elicited their formation
Igs account for what percentage of the total plasma proteins?
*Approx 20%
What is affinity?
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
What is avidity?
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
Avidity is influenced by what factors?
1) The valence of the Ab
2) The valence of the Ag
What is the principle of precipitation?
Soluble Ag + Ab (in proper proportions) -> visible ppt
What is present in precipitation w/c occurs due to the Ag-Ab rxn?
Lattice formation
What is the mechanism of action w/c results to the production of lattice formation?
The Ag binds w/ Fab sites of 2 Abs
What are the exs of the methods employing the principle of precipitation?
1) Double diffusion (Ouchterlony)
2) Single diffusion (Radial immunodiffusion)
3) Immunoelectrophoresis
4) Immunofixation
Where can ppt be observed in precipitation rxns?
In the zone of equivalence
What is present in prozone?
*Ab excess (soluble immune complexes)
Can ppt be formed in the prozone?
No
What is zone of equivalence?
It is where the optimal ratio of Ag/Ab is present
Can ppt be formed in the zone of equivalence?
Yes
What is the characteristic of the ppt that can be formed in the zone of equivalence?
Insoluble ppt
What is present in the post-zone (postzone)?
*Excess Ag (soluble immune complexes)
