LAB METHODS | GUARANTEED SUCCESS STARTS
HERE! LEARN, PRACTICE & EXCEL!
Antigen Detection Method:
what does it look for/ what is it used for?
what does a positive result indicate? Answer: An antigen test looks for an active infection
and is used detect the presence/identity of specific pathogens or foreign substances in a
sample
Used for early diagnosis of an ongoing infection or diagnosis of infectious diseases
more reliable and a positive test result is indicative of a current infection.
Antigen Detection Method:
what tests? Answer: Tests: HIV, Agglutination tests, Fluorescence antibody assays, Enzyme
Immunoassays (ELISA) and Hep. B
Antibody Detection Method:
what does it look for/ what is it used for?
used to assess?
detects? Answer: an antibody test looks for signs of a past infection (exposure to antigen)
and immune responses
- used to determine whether an individual has developed an immune response to a specific
antigen or pathogen.
-Detects the antibodies produced by the host in response to a pathogen
- Used to assess past exposure or immunity
antibody detection methods:
tests? Answer: -Indirect immunofluorescent assays (IFA)
-ELISA
-Western blot
Antibody binds to antigen is affected by what two factors which are what? Answer:
Antibody binding to antigen
- Affected by two factors:
1. Affinity
2. Avidity
1. Affinity definiton
refers to?
IgG? Answer: Affinity:
- The strength of interaction between the epitope and the antigen binding site (Fab) on the
antibody.
- Refers to the strength of a single antibody-antigen interaction.
- Each IgG antigen binding site typically has high affinity for its targets.
2. Avidity definiton
refers to?
IgM? Answer: Avidity:
- The overall binding strength of the Ab-Ag complex.
- Refers to the strength of interactions combined.
APPHIA – Crafted with Care and Precision for Academic Excellence.
1
,IgM typically has low affinity antigen binding sites, but there are ten of them, so avidity is
high.
Antibody binding to antigen:
1. Affinity:
Definition?
Strength is produced by?
Strength: low or high?
what do antibodies require?
What type of antibodies?
Examples? Answer: Antibody binding to antigen:
1. Affinity:
Definition: The attraction which a specific antibody possesses to its corresponding antigen
The strength produced by a single epitope interaction with a paratope on the antibody
Strength: low
Antibodies require a high specificity towards it epitopes
Antibodies are monovalent or divalent
- affinity for one or two epitope(s)
Examples: ABO antibodies, IgG, IgE, and IgD antibodies
Antibody binding to antigen:
1. Avidity:
Definition?
What does it refer to?
Strength is produced by?
Strength: low or high?
antibodies and their specificity?
What type of antibodies?
Examples? Answer: Antibody binding to antigen:
1. Avidity:
Definition: The strength, which an antigen-antibody immune complex possesses at that
epitope
The strength produced by several affinities
Strength: high
Antibodies have less specificity towards their antigen
Antibodies are multivalent
- possess more than one binding site
Examples: IgM
Differentiate acute vs past infection:
IgG
IgM
IgE Answer: IgM: first antibodies produced in response to an infection
-within a couple days to a couple weeks
- high levels of IgM are associated with acute infection (recent);
absence of IgM suggests a past infection or lack of exposure to antigen
APPHIA – Crafted with Care and Precision for Academic Excellence.
2
, IgG: appears after a few weeks of infection
- high levels of IgG are associated with previous infection, past exposure, or immunity to a
particular antigen
IgE: elevated levels indicate allergic response or parasitic infection
- can be elevated in individuals with ongoing allergies or parasitic infections
What are precipitation reactions?
What are they used for? Answer: Used to detect antigen and antibody
Precipitation reactions are reactions in which visible precipitate forms as a result of cross-
linkage (lattice formation) between soluble antigen and antibody.
--show up like crystals of a different color
How do precipitation reactions work? Answer: - The reaction of two soluble reactants that
come together to make one insoluble product
- The binding of soluble Ab to soluble Ag that results in a visible precipitation reaction
- At the zone of equivalence, the ratio or concentration of both antigen and antibody are
equal and results in the precipitate formation
It can be measured by light scattering devices like turbidimeter, nephelometer
What are agglutination reactions? Answer: Agglutination is the formation of clumps of cells
by direct agglutination or passive agglutination
Precipitation reaction results? Answer: positive result is indicated by a precipitate formed
in the zone of equivalence
agglutination reaction results? Answer: Positive reaction of agglutination: is clumps
Negative reaction of agglutination: no clumps; smooth
What do the terms postzone, prozone and zone of equivalence refer to? Answer: used to
describe the relationship between the concentrations of antibodies and antigens and how
they affect the formation of lattice cross-linked precipitates or agglutination.
Prozone: the green portion, has excess of antibody, so no agglutination happening; false
negative rxn can happen
purple part: zone of equivalence, Number of binding site (multivalent sites) of antigen and
antibody reaction is roughly equal, leads to the formation of visible ppt or clumps
Postzone: the orange portion, has excess antigen.
false negative rxn can happen Answer: green part?
purple part?
orange part?
What is the zone of equivalence? Answer: Antigen and antibodies are present in optimal
proportions to bind and produce visible reaction due to clumping/precipitation --> lattice
formation
Prozone:
what is it?
does a lattice form?
does a false negative reaction occur?
what will happen if you dilute the specimen? Answer: When Antibody is in excess
concentration and the ration of antigen to antibody is unbalanced
These antibodies bind to all available antigens but no lattice forms
APPHIA – Crafted with Care and Precision for Academic Excellence.
3
HERE! LEARN, PRACTICE & EXCEL!
Antigen Detection Method:
what does it look for/ what is it used for?
what does a positive result indicate? Answer: An antigen test looks for an active infection
and is used detect the presence/identity of specific pathogens or foreign substances in a
sample
Used for early diagnosis of an ongoing infection or diagnosis of infectious diseases
more reliable and a positive test result is indicative of a current infection.
Antigen Detection Method:
what tests? Answer: Tests: HIV, Agglutination tests, Fluorescence antibody assays, Enzyme
Immunoassays (ELISA) and Hep. B
Antibody Detection Method:
what does it look for/ what is it used for?
used to assess?
detects? Answer: an antibody test looks for signs of a past infection (exposure to antigen)
and immune responses
- used to determine whether an individual has developed an immune response to a specific
antigen or pathogen.
-Detects the antibodies produced by the host in response to a pathogen
- Used to assess past exposure or immunity
antibody detection methods:
tests? Answer: -Indirect immunofluorescent assays (IFA)
-ELISA
-Western blot
Antibody binds to antigen is affected by what two factors which are what? Answer:
Antibody binding to antigen
- Affected by two factors:
1. Affinity
2. Avidity
1. Affinity definiton
refers to?
IgG? Answer: Affinity:
- The strength of interaction between the epitope and the antigen binding site (Fab) on the
antibody.
- Refers to the strength of a single antibody-antigen interaction.
- Each IgG antigen binding site typically has high affinity for its targets.
2. Avidity definiton
refers to?
IgM? Answer: Avidity:
- The overall binding strength of the Ab-Ag complex.
- Refers to the strength of interactions combined.
APPHIA – Crafted with Care and Precision for Academic Excellence.
1
,IgM typically has low affinity antigen binding sites, but there are ten of them, so avidity is
high.
Antibody binding to antigen:
1. Affinity:
Definition?
Strength is produced by?
Strength: low or high?
what do antibodies require?
What type of antibodies?
Examples? Answer: Antibody binding to antigen:
1. Affinity:
Definition: The attraction which a specific antibody possesses to its corresponding antigen
The strength produced by a single epitope interaction with a paratope on the antibody
Strength: low
Antibodies require a high specificity towards it epitopes
Antibodies are monovalent or divalent
- affinity for one or two epitope(s)
Examples: ABO antibodies, IgG, IgE, and IgD antibodies
Antibody binding to antigen:
1. Avidity:
Definition?
What does it refer to?
Strength is produced by?
Strength: low or high?
antibodies and their specificity?
What type of antibodies?
Examples? Answer: Antibody binding to antigen:
1. Avidity:
Definition: The strength, which an antigen-antibody immune complex possesses at that
epitope
The strength produced by several affinities
Strength: high
Antibodies have less specificity towards their antigen
Antibodies are multivalent
- possess more than one binding site
Examples: IgM
Differentiate acute vs past infection:
IgG
IgM
IgE Answer: IgM: first antibodies produced in response to an infection
-within a couple days to a couple weeks
- high levels of IgM are associated with acute infection (recent);
absence of IgM suggests a past infection or lack of exposure to antigen
APPHIA – Crafted with Care and Precision for Academic Excellence.
2
, IgG: appears after a few weeks of infection
- high levels of IgG are associated with previous infection, past exposure, or immunity to a
particular antigen
IgE: elevated levels indicate allergic response or parasitic infection
- can be elevated in individuals with ongoing allergies or parasitic infections
What are precipitation reactions?
What are they used for? Answer: Used to detect antigen and antibody
Precipitation reactions are reactions in which visible precipitate forms as a result of cross-
linkage (lattice formation) between soluble antigen and antibody.
--show up like crystals of a different color
How do precipitation reactions work? Answer: - The reaction of two soluble reactants that
come together to make one insoluble product
- The binding of soluble Ab to soluble Ag that results in a visible precipitation reaction
- At the zone of equivalence, the ratio or concentration of both antigen and antibody are
equal and results in the precipitate formation
It can be measured by light scattering devices like turbidimeter, nephelometer
What are agglutination reactions? Answer: Agglutination is the formation of clumps of cells
by direct agglutination or passive agglutination
Precipitation reaction results? Answer: positive result is indicated by a precipitate formed
in the zone of equivalence
agglutination reaction results? Answer: Positive reaction of agglutination: is clumps
Negative reaction of agglutination: no clumps; smooth
What do the terms postzone, prozone and zone of equivalence refer to? Answer: used to
describe the relationship between the concentrations of antibodies and antigens and how
they affect the formation of lattice cross-linked precipitates or agglutination.
Prozone: the green portion, has excess of antibody, so no agglutination happening; false
negative rxn can happen
purple part: zone of equivalence, Number of binding site (multivalent sites) of antigen and
antibody reaction is roughly equal, leads to the formation of visible ppt or clumps
Postzone: the orange portion, has excess antigen.
false negative rxn can happen Answer: green part?
purple part?
orange part?
What is the zone of equivalence? Answer: Antigen and antibodies are present in optimal
proportions to bind and produce visible reaction due to clumping/precipitation --> lattice
formation
Prozone:
what is it?
does a lattice form?
does a false negative reaction occur?
what will happen if you dilute the specimen? Answer: When Antibody is in excess
concentration and the ration of antigen to antibody is unbalanced
These antibodies bind to all available antigens but no lattice forms
APPHIA – Crafted with Care and Precision for Academic Excellence.
3
