Stimulation of murine hemopoietic colony formation by human IL-6.

A novel hemopoietic CSF has been identified in the medium conditioned by lectin-stimulated human T cells. The cDNA clone encoding this factor, isolated by functional expression cloning in monkey cos-1 cells, proved to be identical with the cDNA encoding the cytokine B cell stimulatory factor-2/IFN-beta 2, a factor now known as IL-6. In the murine system, IL-6 indirectly supports the formation of several different types of hemopoietic colonies, including those derived from early blast cells, and directly supports the proliferation of granulocyte/macrophage progenitors. These results expand the range of known target cells of IL-6 to include hemopoietic progenitors in addition to B cells, T cells, and fibroblasts and provide further evidence that this cytokine plays an important role within a network of interacting cytokines that regulates many different biologic responses.