Measurement of Interleukin 15

Interleukin 15 (IL‐15) is a small helical cytokine that was first characterized by its ability to stimulate proliferation of the murine T cell line CTLL‐2, but is now known to have activity on a variety of cell types. This unit describes two protocols that can be used to measure IL‐15 in culture supernatants and serum samples. The first method uses an enzyme‐linked immunosorbent assay (ELISA) that is specific for human IL‐15, although it can also detect simian IL‐15. The second method relies on the ability of IL‐15 to support proliferation of CTLL‐2 cells. The CTLL‐2 assay is slightly more sensitive than the ELISA, but it is not specific for IL‐15, because CTLL‐2 cells also respond to IL‐2 and IL‐4. The CTLL‐2 assay can be used to measure human, simian, or murine IL‐15.