Elispot

The Enzyme-linked immunosorbent spot (ELISPOT) assay is a common method for monitoring immune responses in humans and animals. It was developed by Cecil Czerkinsky in 1983.[1]

The ELISPOT assay is based on, and was developed from a modified version of the ELISA immunoassay. ELISPOT assays were originally developed to enumerate B cells secreting antigen-specific antibodies, and have subsequently been adapted for various tasks, especially the identification and enumeration of cytokine-producing cells at the single cell level. Simply put, at appropriate conditions the ELISPOT assay allows visualization of the secretory product of individual activated or responding cells. Each spot that develops in the assay represents a single reactive cell. Thus, the ELISPOT assay provides both qualitative (type of immune protein) and quantitative (number of responding cells) information.

By virtue of exquisite sensitivity of the ELISPOT assay, frequency analysis of rare cell populations (e.g., antigen-specific responses) which were not possible before are now relatively easy. This exceptional sensitivity is in part because the product is rapidly captured around the secreting cell: before it is either diluted in the supernatant, captured by receptors of adjacent cells, or degraded. This makes ELISPOT assays much more sensitive than conventional ELISA measurements. Limits of detection are below 1/100,000 rendering the assay uniquely useful for monitoring antigen-specific responses, applicable to a wide range of areas of immunology research, including cancer, transplantation, infectious disease, and vaccine development. The assay has gained a recent increase in popularity, especially as a surrogate measure for CTL responses, in large part because it is both reliable and highly sensitive.

While ELISPOT assay techniques have existed for more than two decades now advancements are still being made in the assay. Modern ELISPOT analysis is typically performed using ELISPOT readers, which employ computer vision techniques to enumerate the actively producing cells. This allows much of the analysis process to be automated, and permits a greater level of accuracy than what can be achieved using manual inspection.