The membrane-bound capture antibody retains the secreted cytokine, antibody, or other target biomolecule close to the cell that released it. A labeled detection antibody then binds the immobilized material, producing a visible spot. This paired-antibody arrangement connects each signal to a producing cell and supports measurement of target-specific secretion.
Spot counts primarily indicate the frequency of cells responding by releasing the measured biomolecule. Spot size or intensity can add information about the amount or degree of secretion associated with those responses. Considering these features together helps distinguish how many cells responded from how strongly they appeared to secrete the target.
Because secreted molecules remain localized near the individual cells that produce them, the assay can reveal responses from cells that represent only a small fraction of the cultured population. This single-cell resolution provides information that would be obscured if all secreted material were considered only as a combined culture-level signal.
Cells are placed in culture on a membrane coated with an antibody that captures the selected secreted molecule. During culture, released material becomes immobilized near its source cell. A labeled detection antibody is then applied to identify the captured molecules, and the resulting visible spots are counted and evaluated.
Researchers apply it to measure antigen-specific T-cell and B-cell responses, evaluate vaccine immunogenicity, investigate pathogen exposure, and assess immune-cell function. These uses make the assay relevant when the central question concerns whether particular immune cells respond to an antigen or pathogen-associated stimulus through secretion.
In infection research, spot patterns can indicate the frequency of immune cells responding to a pathogen-related antigen and can provide additional secretion information through spot size or intensity. The same measurements support comparisons of immune-cell function, pathogen exposure, and vaccine-induced responses when the assay targets the relevant secreted biomolecule.