Which type of ELISA involves binding a known antigen to a plastic well and detecting the specific antigen with an enzyme-conjugated antibody?

The correct choice is the type of ELISA that is characterized by the direct binding of a known antigen to a plastic well, followed by the detection of that specific antigen using an enzyme-conjugated antibody. In a direct ELISA, the known antigen is immobilized on the surface of the well, and the enzyme-linked antibody is applied directly to this antigen. This antibody binds specifically to the antigen, allowing for the detection and quantification of the antigen based on the enzyme's activity.

Direct ELISA is particularly useful for minimizing the number of steps involved in an assay and provides a straightforward approach to antigen detection. Since the assay relies on the direct interaction between the antigen and a specific antibody that is tagged with an enzyme, it allows for quick and reliable results.

In contrast, other types of ELISA, such as indirect ELISA, involve the use of two antibodies (one unlabeled and one enzyme-conjugated) and are typically used to detect antibodies in a sample rather than direct antigen detection. Competitive ELISA involves the competition between different antigens for binding sites on an antibody, while Sandwich ELISA involves capturing an antigen between two antibodies, adding complexity to the process. Each of these methods serves specific purposes in immunological testing but does not align