ELISA and Immunoassays

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Overview

Enzyme-linked immunosorbent assays (ELISAs) are the most common immunoassay type and used to detect the presence and measure the amount/concentration of specific analytes (e.g. antibodies) in a sample. In diagnostics, ELISAs are frequently used to determine whether and how many antibodies have been produced in response to pathogen exposure or vaccination.

ELISA - The Essentials Pocket Guide

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The first step of an ELISA experiment is the immobilization of an antigen present in a sample to the wells of a microtiter plate. This can either be done via adsorption to the plate’s surface or by using a “capture antibody”. The capture antibody has to be specific to the adsorbed antigen and is mainly used in a specific ELISA type called “sandwich ELISA”. After immobilization, a detection antibody is added, which binds to the adsorbed antigen thereby leading to the formation of an antigen-antibody complex. The detection antibody is either directly conjugated to an enzyme, such as horseradish peroxidase (HRP), or provides a binding site for a labeled secondary antibody.

In general, ELISAs can be grouped into the four main categories (direct ELISAs, sandwich ELISAs, competitive ELISAs and dip-stick ELISAs), details of which are included in our Introduction to ELISA guide. To find out more about which ELISA set-up is best for your experimental needs, please refer to our comprehensive Guide to ELISA applications.