ag-ab reactions
DESCRIPTION
Ag-Ab ReactionsTRANSCRIPT
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Principles of ImmunologyAntigen-Antibody Interactions4/25/06
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Word/Terms List
Agglutinin EIAEquivalence zone FIAImmunodiffusionImmunoelectrophoresisRIATiter
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Affinity = attractive and repulsive forcesAffinityStrength of the reaction between a single antigenic determinant and a single Ab combining site
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SpecificityThe ability of an individual antibody combining site to react with only one antigenic determinant.The ability of a population of antibody molecules to react with only one antigen.
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Cross ReactivityThe ability of an individual Ab combining site to react with more than one antigenic determinant.The ability of a population of Ab molecules to react with more than one Ag
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Factors Affecting Measurement of Ag/Ab Reactions Affinity Avidity Ag:Ab ratio Physical form of Ag
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Tests Based on Ag/Ab ReactionsAll tests based on Ag/Ab reactions will have to depend on lattice formation or they will have to utilize ways to detect small immune complexesAll tests based on Ag/Ab reactions can be used to detect either Ag or Ab
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Agglutination TestsLattice Formation
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Agglutination/HemagglutinationDefinition - tests that have as their endpoint the agglutination of a particulate antigenAgglutinin/hemagglutinin
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Agglutination/HemagglutinationQuantitative agglutination testTiterProzone
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Agglutination/HemagglutinationDefinition Qualitative testQuantitative test Applications Blood typing Bacterial infectionsFourfold rise in titer Practical considerations Easy Semi-quantitative
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Passive Agglutination/HemagglutinationDefinition - agglutination test done with a soluble antigen coated onto a particle
ApplicationsMeasurement of antibodies to soluble antigens
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Agglutination/Hemagglutination InhibitionDefinition - test based on the inhibition of agglutination due to competition with a soluble Ag
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Agglutination/Hemagglutination InhibitionApplicationsMeasurement of soluble AgPractical considerationsSame as agglutination test Definition
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Precipitation TestsLattice Formation
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Radial Immunodiffusion InterpretationDiameter of ring is proportional to the concentrationQuantitativeIg levels Method Ab in gel Ag in a well
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ImmunoelectrophoresisMethodAgs are separated by electrophoresis Interpretation Precipitin arc represent individual antigens
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ImmunoelectrophoresisMethodInterpretationQualitativeRelative concentration
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Radioimmuoassays (RIA)Enzyme-Linked Immunosorbent Assays (EIA)Lattice formation not required
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Competitive RIA/ELISA for Ag MethodDetermine amount of Ab needed to bind to a known amount of labeled Ag
Use predetermined amounts of labeled Ag and Ab and add a sample containing unlabeled Ag as a competitor
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Solid Phase Non-Competitive RIA/ELISAAb detectionImmobilize AgIncubate with sampleAdd labeled anti-IgAmount of labeled Ab bound is proportional to amount of Ab in the sample
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Solid Phase Non-Competitive RIA/ELISAAg detectionImmobilize AbIncubate with sampleAdd labeled antibodyAmount of labeled Ab bound is proportional to the amount of Ag in the sample
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Tests for Cell Associated AntigensLattice formation not required
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Immunofluorescence Direct Ab to tissue Ag is labeled with fluorochrome
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ImmunofluorescenceIndirectAb to tissue Ag is unlabeledFluorochrome-labeled anti-Ig is used to detect binding of the first Ab.Qualitative to Semi-Quantitative
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Assays Based on ComplementLattice formation not required
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Complement FixationAg mixed with test serum to be assayed for AbStandard amount of complement is addedErythrocytes coated with Abs is addedAmount of erythrocyte lysis is determinedAg Ag
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