Immunoassays

Question 1

Briefly explain 2 uses for solid phase binding immunoassays for Abs? (2marks)

Answer 1

screen hybridoma supernatants

detect exposure to infectious agents

Question 2

state 2 forms of immunoassays and state what each form does? (2marks)

Answer 2

solid phase binding assays = quantifies Abs

two site assays = quantifies Ags

Question 3

Explain 3 ways Abs can be identified and quantified by diagnostic techniques? (3marks)

Answer 3

nephlometry = presence of individual isotopes 
RAST = Abs against particular allergen
immunofluorescence = Abs against self Ags

Question 4

Explain briefly how Abs can be used in monitoring HIV infection is the clinic? (3marks)

Answer 4

lymphocyte subset estimations performed using monoclonal Abs to CD3/4/8 on whole body and analysed by flow cytometry.
percentage of cells in each subset determined using FACs machine.
results reported as percentages and absolute counts/

Question 5

briefly describe how solid-phase binding immunoassays for Abs work?

Answer 5

antigen immobilised on solid support –> test Ab solution added –> incubated –> non-bound removed by washing –> bound Ab detected by incubation with labelled 2nd Ab and non-bound removed by washing

Question 6

briefly describe how two-site (sandwich) assays for Ags work? (4marks)

Answer 6

you need 2 Abs reacting with different epitopes on Ag -> 1 Ab immobilised on solid support –> test Ag solution added –> incubated –> non-bound removed by washing –> bound detected by incubation with other AB which is labelled

Question 7

why is it useful to detect autoantibodies in terms of SLE disease and name 2 techniques used to identify Abs (3marks)

Answer 7

for diagnosis and disease activity.
ELISA
immunofluorescence

Question 8

in the case of immunodeficiency which 2 techniques are used in quantifying the presence or absence of Abs? (2marks)

Answer 8

electrophoresis

nephelometry