Antibody-Antigen Interactions/Immunoassays Flashcards Preview

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Flashcards in Antibody-Antigen Interactions/Immunoassays Deck (13):

What is antibody affinity?

expression of the sum of all the interactions between an Ab binding site and its homologous Ag, only precise in a monovalent Ag-Ab system with monoclonal Ab


What is antibody avidity?

strength of binding of multivalent antiserum to multivalent Ag, (antiserum contains many Ab species which can bind to multiple epitopes on the Ag)


Why does cross-reactivity for Ag exist in antiserum? (multiple Abs exist in antiserum for a specific Ag)

impurity in immunizing agent that may be better Ag than the target Ag, similarity in structures/epitopes of Ags


What two ways are used to eliminate cross-reactivity?

absorption, affinity chromatography


Describe how absorption is used to eliminate cross-reactivity.

immobilizing the protein/Ag that unwanted Ab is specific for and exposing antiserum to it, keep what washes off/doesn't absorb
-eliminates activity that have been there (to bind to the proteins)
-remove contaminating Ab


Describe how affinity chromatography is used to eliminate cross-reactivity.

-purify Ab you want
-immobilize protein specific for the target Ab and keep only the Ab that binds to it, wash the others away, acid release/detergent wash of Ab-Ag to release the Ab of interest
-purifies for certain specificity


Why are monoclonal antibodies important?

binds only one epitope for specificity, clone can survive indefinitely, huge amount of Ab can be produced, less crossreactivity


Describe the preparation of monoclonal Ab

1. Immunize animal
2. Isolate spleen cells from immunized animals (Bcells)
3. Fuse spleen cells to plasmacytoma tumor cells that are nonsecretors, but produce tons of Ab once get the gene from the B cell.
4. Select for only those cells that are hybrids of tumor cells and B cells.
5. Clone hybridomas so each cell grows up independently.
6. Select the individual clone with the specificity of interest.


What are the negatives of monoclonal Ab?

some assays need higher affinity than monoclonals can provide, no avidity in response


What are chimeric monoclonal Ab?

variable regions are mouse monoclonal, constant regions are human


What are humanized monoclonal Ab?

only the points of contact with the Ag remain mouse


What causes serum sickness?

hypersensitivity response caused by Ab against non-human Ab forming immune complexes in serum, secondary exposure can be deadly


What does immunofluorescence allow the identification of?

specific cell type, cell structure, pathogen, enzyme activity based on antibody specificity or enzyme specificity