lecture 15 Flashcards
(16 cards)
Explain serological testing what is detected
Serological testing performed on blood samples or serum can measure ag-Ab binding in vitro detects ag look ab specific for ag of interest quantify ag or ab, to look if levels are increasing over time detect types of ab present (igG)
What is antibody titre
Antibody titre
level fo specific ab present
defines if the ab is present or not and the levels of ab present
its a measurement not the absolute
concentration
if the sample has a higher titter you can dilute it more and still get a positive results
its the most diluted sample and you can still get a positive results
Define sensitivity
Sensitivity- probability that a given test will correctly id animals with the disease
Define specificity
Specificity- a test which will id those animals which don’t have the disease
What is antiserum
Antiserum= serum collected from animal which has been exposed to the ag and has ab against the ag
it requires the animal to be immunised with ag to have the ab
or you can inject ab and the ab becomes ag and you can produce ab against the infected ab
they are produced in 1 species and injected into another
When is an Immunoassay
Immunoassays measure ab which can be used to detect exposure to microbe
Explain what would occur if
- IgG and IgM is negative
- IgG ab positive IgM ab negative
- IgG and IgM ab positive
- IgG ab negative, igM ab positive
if IgG and IgM is negative, animal isn’t infected or its to early to tell yet
IgG ab positive IgM ab negative, animal has been exposed previously or vaccinated
IgG and IgM ab positive the animal has a current or recurrent infection
IgG ab negative, igM ab positive, animal is very early in the acute phase of the infection or you get a false positive
When would a false negative occur?
False negative
if animal has low ab titre and the test isn’t; sensitive enough
-its too early in the infection
-some animals can’t make ab response like immunodepressed
When would a false positive occur?
false positive
exposure to a different virus with the same epitope
-animal has been vaccinated with attenuated version of the pathogen
List the samples used in imunodiagnostic tests
Blood (plasma or serum, cellular fraction of the blood)
- Urine, milk, tissue, fluid
- Tissue biopsy
- In Vivo tests
List the common immunodiagnostic test
immunodiagnostic test
- agglutination test
- precipitation test (KNOW this)
- enzymes-linked immunosorbent assay (ELISA)
- immunochromatography (snap test)
- Haemagglutination inhibition test
- complement fixation test
What is an ELISA
ELISA
-detect ag or ab
used from serum, secretion
enzymes linked immunosoborent assay
When should you use competitive ELISA
when to use a competitive ELISA
when there is considerable cross-reaction between viruses, so the symptoms are very
similar
could use indirect ELISA but you will only get a positive results and you will not know if its the true virus or the look a like.
an example is blue tongue virus and other viruses
What is a sandwich or capture ELISA
sandwich or capture ELISA
used to detect Ag, abs, cytokines and other proteins
need matched pairs of ab
List the steps of an non-competitive indirect ELISA
Steps of non-competitive indirect ELISA
step 1) Coat wells in ag, wash
step 2) add serum sample from animals which will have ab or not, wash
step 3) add conjugate , its an ab which is linked to secondary ab which is usually anti species ab, wash
step 4) add substrate which will change colour if abs are present
washing removed anything which is not
bound
the greater the colour change the more ab present
List the steps for a competitive indirect ELISA
steps for a competitive indirect ELISA
-step 1) Coat wells in ag, wash
step 2) add serum sample from animals which will have ab or not, wash
step 3) add conjugate , its an ab which is linked to secondary ab which is usually anti species ab, this will competing to bind to the ag with the ab which may or mayn’t be present in the animals sample, wash
step 4) add substrate which will change colour if there is no abs are present in the sample
washing removed anything which is not bound
the more colour present the less ab present
