ELISA and Immunofluorescent Assays - Vocabulary Flashcards

Vocabulary flashcards covering key ELISA and immunofluorescent assay concepts from the lecture notes.

ELISA (Enzyme-Linked Immunosorbent Assay)

A plate-based assay that uses antigen–antibody interactions with an enzyme-labelled detector antibody and a chromogenic substrate to produce a measurable color change.

Antigen

A substance that is recognized by an antibody; the target of detection in many ELISAs.

Antibody

A protein produced by B cells that binds specifically to an antigen.

Chromogenic substrate

A substrate that, when acted on by a conjugated enzyme, produces a color change measurable in ELISA.

Enzyme-labeled antibody

An antibody conjugated to an enzyme used for detection in ELISA.

Horseradish peroxidase (HRP)

A common enzyme used in ELISA that catalyzes color-producing reactions with chromogenic substrates.

Optical density (OD)

A measure of color intensity (absorbance) used to quantify ELISA results.

Calibrators/Standards

Known concentrations used to generate a reference curve for interpreting patient samples.

Blank

A control well with no antigen or antibody complexes used to measure background signal.

Direct ELISA

An ELISA where the primary antibody is directly conjugated to the detection enzyme to detect antigen.

Indirect ELISA

An ELISA where a secondary antibody conjugated to an enzyme binds to the primary antibody, enabling detection of the antibody in the sample.

Noncompetitive ELISA

An antibody-detection ELISA in which antigen is bound to the plate, the patient’s antibody binds to it, and an enzyme-labeled anti-human antibody binds to that antibody; color is proportional to antibody amount.

Competitive ELISA

An ELISA in which labeled antibody competes with the patient’s antibody for antigen binding sites; color change is inversely proportional to antibody amount.

Capture ELISA

An ELISA where an antibody bound to the plate captures the target antibody or antigen; often used to detect IgM or IgG.

IgM

An immunoglobulin class produced early in infection, indicating acute phase.

IgG

A later-stage immunoglobulin indicating past exposure or immunity.

Equivocal

An indeterminate test result lying in a gray area between negative and positive; may require retesting.

Fluorophore

A molecule that emits fluorescence after excitation, used to label antibodies in immunofluorescent assays.

Fluorescein isothiocyanate (FITC)

A common fluorophore covalently attached to antibodies for fluorescence detection.

Immunofluorescent assay (IFA)

An assay using fluorescent labels to detect antigen or antibody, read under a fluorescence microscope or instrument.

Direct fluorescent antibody (DFA)

A direct immunofluorescent assay where a fluorophore-conjugated antibody binds directly to the target antigen.

Indirect fluorescent antibody (IFA)

An indirect immunofluorescent assay that uses a secondary fluorescent antibody to detect the presence of the target antibody bound to antigen.

Transmitted-light fluorescence microscope

A fluorescence microscope that excites and detects fluorescence using light transmitted through the specimen with a condenser.

Incident-light fluorescence microscope

A fluorescence microscope that uses reflected (incident) light to detect fluorescence, typically without a transmitter condenser.

Microtiter plate

A plate with multiple wells used to perform ELISA assays; each well is a reaction chamber.