Interleukin 1 regulates hematopoietic activity, a role previously ascribed to hemopoietin 1

A murine in vitro assay was developed to measure potentiation of a proliferative response to suboptimal concentrations of the hematopoietic regulatory molecule granulocyte/macrophage colony-stimulating factor by an immature bone marrow population. The assay, designated the 5-fluorouracil bone marrow proliferation assay, was used to characterize potentiating activity in serum-free culture supernatants of the human tumor cell line HBT 5637. Molecular and biochemical analyses indicated that the HBT 5637-derived potentiating activity could be attributed to interleukin 1 alpha. Serologic analysis using a monoclonal antibody against purified recombinant interleukin 1 alpha proved conclusively that the potentiating activity in HBT 5637 serum-free supernatants is due to interleukin 1 alpha. From these data, the activity of interleukin 1 alpha seems to be the same synergistic activity formerly ascribed to hemopoietin 1.