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42 Cards in this Set

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  • Back
what is the fundamental reaction of immunology?
Ab+Ag > Ab-Ag
What makes it possible to perform qualitative and quantitative assays on the Ag-Ab system?
Macromolecular antigens and antibodies frequently form compleses that become insoluble and precipitate from solution.
Precipitation occurs?
Because each Ab can bind to more than one Ag and each macromolecular Ag can be bound by more than one Ab.
Ag is added to a constant amount of Ab in solution
Antibody-excess zone?
Initially, the amount of the Ab in solution is much greater than the amount of Ag in solution. Ab>Ag.
Equivalence zone, or equivalence point?
As more An is added, the amount of protein precipitated increases until the antigen and antibody molecules are at an optimal ratio (roughly equal proportions). Ab=Ag.
Where maximum precipitation occurs.
Antigen-excess zone?
When the amount of Ag in solution exceeds the amount of Ab, the amount of precipitation. Ag>Ab
When Ab and Ag are inserted into diff. areas of an agarose gel?
They diffuse toward each other and form opaque bands of precipitate at the interface of their diffusion fronts
Precipitation reactions of Ab and Ag in agarose gells provide?
A method of analyzing the various Ab-Ag reactions in a system.
Double diffusion in two dimensions
Diffuse from the wells toward each other >> precipitate where they meet at equivalent proportions.
A single Ag will combine w/ ?
its homologous Ab to form a single precipitation line.
When two Ag are present?
Each behaves independently of each other.
The number of precipitin bands indicates?
There are at least that many Ab-Ag systems present.
Double diffusion in 2-D is a useful technique for?
Comparing Ag for the number of identical or cross-reacting determinants.
Reaction of Identity?
A soln of Ag is placed in 2 adjacent wells and the homologous Ab is placed in the center well, the 2 precipitin bands that form will join at their closest ends and fuse.
Reaction of non-identity?
When unrelated Ag’s are placed in adjacent wells and the center well is filled w/ Ab for each Ag. The precipitin bands will form independently of each other & will cross.
When will the precipitin lines fuse?
When the Ag in one well & the antiserum in the center well = homologous pair.
And the Ag in an adjacent well is a cross-reacting Ag.
Partial identity?
When the precipitin lines fuse an additional spur occurs projecting towards the cross-reacting antigen.
The spur projects towards?
The Ag with the fewer determinants (i.e. cross-reacting Ag).
The spur represents?
The reaction b/t homologous Ag and those Ab molecules that do not combine with the cross reacting Ag.
Homologous Ag contains determinants (recognized by hom. Ab) which are NOT present on x-reacting Ag.
Why is the spur usually less dense than the precipitin ban from which it projects?
Non-cross-reacting antibodies often compose only a fraction of the total antibody involved in the homologous precipitin reaction.
Ab-Ag interactions are usful in the ?
Defense of the body against bacterial and viral infections and toxins.
The defense capabilities are dependent upon?
The recognition of Ag by humoral components of the immune system.
Specific Ab are then produced in response to exposure to the Ag.
The formation of Ag-Ab complexes is the first step in?
Removing infectious agents from the body.
Because each Ab can bind more than one Ag and each Ag can be bound by more than one Ab?
Very large macromolecular complexes can form
Very large macromolecular compleses form?
Precipitates which can be cleared from the body through various themes.
These precipitates are also useful for?
Laboratory and diagnostic tests.
Precipitation reactions of Ab and Ag in agarose gells provide ?
A method of analyzing the various Ab-An reactions in a system.
A single Ag will combine with its homologous Ab to form a single precipitation line.
Radial Immunodiffusion (RID)?
Is a technique that can quantitatively determine the concentration of an Ag.
RID is used for?
Sensitive quantitative technique that is often used clinically to detect patient levels of blood proteins.
Agarose contains?
Ab is incorporated into molten agarose > gel
Small well?
Are filled with known concentrations of Ag which corr. To the Ab in the agarose.
Samples of unknown concentrations are pplaced in similar wells.
The antigen soln?
Diffuse outwards from the well in a circular pattern surrounding the well.
Is present in excess & diffusion of the Ag will continue until a stable ring of Ag-Ab precipitate forms.
There are Ag-Ab complexes?
Throughout the zone surrounding the well w/in the precipitin line.
Equivalence zone or equivalence point?
At the precipitin line is where the greatest # of complexes can be found
b/c the Ag and Ab are present in roughly equal proportions.
How long does it take?
24 to 48 hours for optimal diffusion to occur and precipitation to b/c apparent.
For each antigen?
An endpoint precipitation ring of a certain D will form
From the known standard concentrations?
A standard curve can be drawn by plotting Ag concentration versus the D^2 measurements of the rings.
From the linear calibration curve?
The concentration of the unknown samples may be determined.