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.