Immunoassays Flashcards
who proposed that antigen combined with pre-existing side-chains on cell surfaces.
ehrlich
what is the basis of immunoassays
specific binding between Ag and corresponding Ab
what kind of bond is Ab-ag
non covalent
is the binding of Ab and Ag reversible
yes
def? the initial force of attraction that exists between a single Fab site on an antibody molecule and a single epitope site on the corresponding antigen
affinity
def? the overall strength of antigen-antibody binding and is the sum of the affinities of all the individual antibody-antigen combining sites.
avidity
what is cross reactivity
ab reacting with ag that is structurally similar to the homologous ag
what kind of immunochemical method is precipitation and light scattering
direct
what kind of immunochemical method is label methods
indirect
what immunoassays fall under the precipitation category
immunodiffusion and immunoelectrophoresis
what immunoassays fall under the light scattering category
nephelometry and turbidimetry
what immunoassays fall under the label method category
non competitive, competitive, heterogeneous, homogeneous
Immunoassays that detect antigen-antibody complex formation directly without labels are known as _____ or _______ immunoassays
direct; non labeled
is a label involved in precipitation immunoassays
no
are precipitation assays qualitative or quantitative
both
major components of direct assays
solution, gel, instrument
where are ag and ab in a direct immunoassay
diffusing into the solution
what factors affect solubility
size, charge, temp, and solvent ionic strength
describe the prozone
ab is in excess
describe the zone of equivalence
ab and ag are equal
describe the postzone
ag is in excess
does precipitate form in the prozone and postzone
no
A patient’s sample contains equal amount of Ab and Ag, but the reaction in a test system containing antigen is negative (no ppt). What has happened?
low specificity
t or f: Precipitation reactions in gel are not commonly performed in the clinical laboratory today
T
what is gel made out of
dilute agarose
what kind of buffer is used for gel electrophoresis precipitation
aqueous
what kind of medium is gel considered
semisolid
what kind of assay do immune complexes separate more easily
gel
in double diffusion radial immunodiffusion does the Ab or Ag diffuse into the gel
both
where is the Ag placed in double radial immunodiffusion
center well
where is the Ab placed in double radial immunodiffusion
in the wells surrounding the center well
what kind of diffusion technique is radial immunodiffusion
double diffusion and single
is double radial immunodiffusion qualitative or quantitative
qualitative
what does single radial immunodiffusion quantitatively determine
Ag
where is the Ab in single radial immunodiffusion
incorporated into liquefied agar
where is the Ag in single radial immunodiffusion
well
how is the amount of Ag quantified in radial immunodiffusion
by the amount of diffusion
how is the amount of Ag quantified in single radial immunodiffusion
diameter of ppt ring
what math equation can you use to determine conc of Ag in single radial diffusion
standard curve
what are the Y and X axis of the standard curve
Y axis: diameter of the ring
X axis: conc of Ag