CTL ELISPOT Assay and T Cell Detection

Enzyme-linked immune absorbent spot (Elispot) is a quantitative method for measuring relevant parameters of T-cell activation. The sensitivity of Elispot allows the detection of low-frequency antigen-specific T-cells that secrete cytokines and effector molecules, such as granzyme B and perforin. Cytotoxic T-cell (CTL) studies have taken advantage with this high-throughput technology by providing insights of quantity and immune kinetics. Accuracy, sensitivity, reproducibility, and robustness of Elispot resulted in a wide range of applications in research as well as in diagnostic field. Actually, CTL monitoring by Elispot is a gold standard for the evaluation of antigen-specific T-cell immunity in clinical trials and vaccine candidates where the ability to detect rare antigen-specific T-cells is of relevance for immune diagnostic. The most utilized Elispot assay is the Interferon-gamma (IFN-γ) test, a marker for CD8+ CTL activation, but Elispot can be also used to distinguish different subsets of activated T-cells by using other cytokines such as T-helper (Th) 1 type cells (characterized by the production of IFN-γ, IL-2, IL-6, IL-12, IL-21 and TNF-α), Th2 (producing cytokines like IL-4, IL-5, IL-10 and IL-13), and Th17 (IL-17) cells.