ISO 15089:2000 水質—植物処理および農薬を決定するための選択的イムノアッセイのガイドライン | ページ 2

3.1

affinity

strength of binding of antibody to analyte

Note 1 to entry: The strength is defined by the equilibrium constant ( K ) of the reaction Ab + H = AbH, where Ab = antibody combining site and H = hapten; K is given by the mass action equation K = c_AbH/( c_ab × c_H).

3.2

analyte

substance to be determined

3.3

antibodies

serum proteins produced in vertebrates in response to immunization and which selectively bind the antigen or hapten, respectively

Note 1 to entry: Monoclonal antibodies (mAb) are uniform populations of antibodies which are produced from a single cell clone of hybridoma cells.

Note 2 to entry: Polyclonal antibodies (pAb) are a mixed population of antibodies which are produced by several clones of plasma cells.

Note 3 to entry: Recombinant antibodies (rAb) are produced using recombinant techniques established in gene technology.

3.4

antibody conjugate

antibody covalently linked to a label such as an enzyme or a fluorochrome

3.5

antigen

substance that stimulates the production of antibodies and reacts with them

3.6

antiserum

immune serum obtained from the blood of immunized vertebrates after removal of cellular components and coagulation factors

Note 1 to entry: It usually contains a number of different antibodies which can exhibit different affinities to the antigen/hapten.

3.7

coating conjugate

macromolecule bound to the hapten (also known as a hapten-carrier conjugate), which is immobilized to a solid phase

Note 1 to entry: It is used to bind those antibody binding sites which are not occupied by the analyte.

3.8

competitive immunoassay

test which detects the proportion of antibody binding sites which have been occupied by the sample analyte

Note 1 to entry: This is achieved by adding a tracer which binds to the unoccupied antibody binding sites and produces the measuring signal after a further reaction.

3.9

cross-reactivity

extent, to which an antibody or an antiserum reacts with a substance which structurally differs from the analyte

Note 1 to entry: The cross-reactivity of an antibody or an antiserum with this substance is determined by comparing the calibration curves. The reference curve obtained with the analyte is used as reference quantity (= 100 % cross-reactivity). The crossreactivity is usually determined at the IC₅₀. The selectivity of an antibody or an antiserum, respectively, is inversely related to the cross-reactivities. An antibody or an antiserum, respectively, can display different affinities to different substances. With a given substance, the cross-reactivity of an antiserum can also vary within the measuring range. Usually the structure of the immunogen essentially determines the selectivity (the so-called specificity) of an antiserum. If cross-reactivities are due to a mixed population of antibodies as often occurs in an antiserum, the undesired antibodies may be removed by cross-absorption.

Note 2 to entry: All compounds (present in relevant concentrations) that exhibit cross-reactivity will create false positive results.

3.10

enzyme immunoassay

EIA

immunochemical analysis which detects the occupancy of antibody binding sites by the analyte with the aid of a tracer (an enzyme-labelled hapten or an enzyme-labelled antibody) and consequently can be used to detect the analyte concentration in the medium

Note 1 to entry: The detection procedure is based on the measurement of the enzyme activity of the tracer by means of substrate conversion.

3.11

enzyme substrate

substance which is converted by the enzyme into a product that can be detected by a measuring device

3.12

excess standard

analyte concentration which, once exceeded, produces no further decrease in the signal measured in the immunoassay

3.13

fluorescence immunoassay

immunochemical detection procedure which is performed either as an immunoassay with fluorescent substrates or products, respectively, or as an immunoassay with fluorescence-labelled tracers or antibodies, respectively

3.14

hapten

substance which, because of its small molecular size, does not evoke the production of antibodies unless it is covalently bound to an immunogen

Note 1 to entry: Pesticides are examples of haptens.

3.15

heterogeneous immunoassay

test which requires a separation of solid phase-bound and unbound tracers in order to detect the occupancy of antibody binding sites by the analyte and thus the analyte concentration in the sample

3.16

immunoassay

quantitative assay which is based on the selective analyte/antibody binding and uses tracers for the detection of the free or occupied antibody binding sites, respectively

3.17

immunogen

substance which triggers an immune response after injection into a vertebrate

3.18

inhibition concentration

IC

analyte concentration which reduces the measuring signal of the zero standard (= 100 %), in the case of IC₅₀ to 50 % of the zero standard

3.19

luminescence immunoassay

LIA

immunochemical assay which is either performed as an immunoassay detecting luminescent substrate or product, respectively, or luminescence-labelled tracer

3.20

solid phase immunoassay

heterogeneous immunoassay which uses (depending on the test type) antibodies or coating conjugates, immobilized to a solid phase

Note 1 to entry: Usually, both test types are known as ELISA (enzyme-linked immunosorbent assay) when enzyme-labelled tracers are used.

3.21

tracer

labelled hapten (or antigen) or labelled antibody which, in the case of competitive immunoassays, is used to detect the percentage of antibody binding sites not being occupied by the analyte

3.22

zero standard

analyte-free standard (method blank) which is used for calibration