Exam 2: Immunoassay definitions Flashcards
Anti-antibody
An antibody with specificity for immunoglobulins
Antibody
Immunoglobulin (Ig) class of molecule, with five main types: IgA, IgD, IgE, IgG, and IgM
Antigen
Any material capable of binding to an antibody, without necessarily being capable
of inducing an immune response
Competitive immunoassay
A reagent-limited immunoassay in which labeled and unlabeled
species compete to generate a signal; in the original format,
antibody-bound and free fractions of labeled antigen are separated
by, e.g., centrifugation and decantation of the free fraction
Conjugate
To link, chemically or physically, two or more distinct molecules; for example, in
immunoassays a hapten may be conjugated to a carrier protein, or an enzyme may
be conjugated to an antibody
Cross-reactivity
Binding of an antibody to an antigen other than the one initiating the
immune response
ELISA
Enzyme-linked immunosorbent assay; a type of sandwich enzyme immunoassay
in which one of the reaction components is attached to the surface of a solid phase
to facilitate separation of bound and free labeled reactants
EMIT
Enzyme-multiplied immunoassay technique; a nonseparation immunoassay using
an enzyme label
Epitope
The specific portion of a macromolecular antigen (“molecular features”) to which
an antibody or a T cell receptor binds; an antigenic determinant (see hapten,
below)
FPIA
Fluorescence polarization immunoassay
Hapten
A compound, usually of low molecular weight, that is not itself immunogenic, but
becomes immunogenic and induces an antibody response after conjugation to a
carrier protein or to cells. The hapten alone can bind to the antibody in the
absence of carrier.
Heterogeneous assay
Immunoassay format that uses two phases, usually liquid and solid, to
separate reacted/bound from unreacted/unbound components
Homogeneous assay
Labeled-analyte immunoasay format that does not require separation of
bound and free antigen
Immunogen
A substance capable of inducing an immune response
Immunoglobulin (Ig)
A protein with antibody activity
Immunometric assay
Immunoassay format using labeled antibody to bind antigen, with two
main subdivisions: single-site, and two-site
Interference
Any factor causing bias in an assay result, other than the presence of a true
cross-reacting substance (in an immunoassay)
IRMA
Immunoradiometric assay; a type of two-site immunoassay using radioisotopes as
the label on the antibody
Isotope
Atomic species that, in the nucleus, have the same number or protons but a
different number of neutrons
Label
Any substance with a measurable property that can be attached to an antigen,
antibody, or other binding substance (such as biotin, protein A, avidin, etc.);
includes chromophores, fluorophores, radioactive isotopes, enzymes, etc.
Monoclonal antibody
A monospecific antibody that is produced by a single plasma cell or a
single clone of plasma cells
Polyclonal antibodies
A heterogeneous mixture of antibodies with diverse affinities toward an
antigen; produced by a large number of plasma cell clones
Radiolabel
A radioactive label; a label using unstable isotopes that spontaneously transform
to a more stable state, emitting energy in the form of particles or electromagnetic
pulses
RIA
Radio-immunoassay; a heterogeneous competition immunoassay that uses
radiolabeled antigens or antibodies; in the original liquid-phase format, the assay
would require a precipitation step to separate antibody-antigen complexes;
modern forms use antibodies bound to polystyrene assay tubes or wells
