Induction of hybridoma growth factor (HGF), identical to IL-6, in human fibroblasts by IL-1: use of HGF activity in specific and sensitive biological assays for IL-1 and IL-6.

Human hybridoma growth factor (HGF) has been purified to homogeneity and identified with the 26kDa protein, interferon-beta 2 (IFN-beta 2), B-cell stimulatory factor-2 (BSF-2) and hepatocyte stimulatory factor (HSF). This factor, renamed interleukin-6 (IL-6), can be induced in fibroblasts by IL-1, while other cytokines are less active or inactive as inducers. The possible use of this IL-6 induction as an alternative indirect assay system for IL-1 is considered. Also, the direct HGF activity as a test IL-6 has been compared with the other biological activities of IL-6. It was concluded that the HGF assay is the most sensitive, specific and convenient test for IL-6.