In the enzyme-linked immunosorbent assay (ELISA), what can be attached to a solid phase support?

In an enzyme-linked immunosorbent assay (ELISA), the solid phase support is crucial for capturing the target molecules, which can either be antibodies or antigens. This solid phase, typically a plate made of polystyrene, is coated with either a specific antibody that will bind to the antigen of interest or an antigen that will bind to a specific antibody in the sample.

The choice of attaching an antibody or an antigen allows for the selective binding that is fundamental to the assay's specificity. When the sample is added, the target molecule in the sample will bind to the coated surface if there is a match. This binding is the first crucial step in the assay, which is then followed by other steps including the addition of enzyme-labeled antibodies, substrate, and ultimately the detection of the enzyme reaction.

The other options—enzyme or substrate, fluorochrome or dye, and cell or tissue—do not serve the same purpose in the ELISA process. Enzymes and substrates are involved in the reaction that produces a measurable signal, but they are not attached to the solid support; they are typically introduced in later steps. Similarly, fluorochromes and dyes can be used for detection but aren't tied to the initial binding steps of the assay