Identification of a 24-kDa cytokine that is required for development of cytolytic T lymphocytes (dendritic cells/interleukin 2/cytotoxdc differentiation factor/lymphokines)

It Is known that the production of cytolytic T lymphocytes requires growth factors such as Interleuklns 2 and 4 (IL-2 and IL-4). Elsewhere we have described bloassays that detect a cytokine that operates In concert with growth factor to generate cytolytic T lymphocytes. The factor that is termed cytolytic T-lymphocyte differentiation factor (CDF), together with IL-2 and lectin, mediates the formation of CD8+ killer cells In 2 days from thymocyte or peripheral lymphoid precursors. CDF Is not mimicked by natural or recombinant sources of Interferons, colony-stimulating factors, and IL1 to IL-4. Here we use these bloassays to Isolate and further characterize a single 24-kDa CDF protein from the condi- tioned medium of stimulated human blood mononuclear cells. CDF Is first enriched by three successive chromatographic procedures that utilize anion exchange, hydroxyapatite, and phenyl-Superose. A single 24-kDa band with CDF activity Is