Final answer:
An enzyme immunoassay (EIA), like the capture EIA or ELISA, utilizes the specificity of antibody-antigen interactions along with an enzyme-conjugated antibody to generate a colorimetric signal. This allows for the detection and quantification of antigens. Immunostaining is another application of EIA, often used in tissue examination.
Step-by-step explanation:
A Capture Enzyme ImmunoAssay (EIA) or enzyme immunoassay, is a laboratory technique used to detect the presence and quantity of antigens using highly specific antibody-antigen interactions. This technique employs antibodies coupled to enzymes that can generate an observable signal, typically a color change, on a colorless substrate. This process involves multiple steps, beginning with the capture of the antigen by an antibody fixed to a solid surface, followed by a washing phase to remove unbound substances, the addition of an enzyme-linked antibody specific for the antigen, and the application of a chromogenic substrate that induces a visible signal indicating the presence of the antigen.
One common version of EIA is the enzyme-linked immunosorbent assay or ELISA. In this assay, the antigen is immobilized within a microtiter plate well, and detection involves an antibody conjugated to an enzyme. Following the binding of the enzyme-conjugated antibody to the antigen and subsequent washing, a substrate that reacts with the enzyme is introduced, leading to a color change if the antigen is present.
Another application of EIA includes immunostaining, particularly useful in examining tissues via immunohistochemistry to visualize specific cell types or to localize antigens within tissue sections.