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 1α . Serologic analysis using a monoclonal antibody against purified recombinant interleukin 1α proved conclusively that the potentiating activity in HBT 5637 serum-free supernatants is due to interleukin 1α . From these data, the activity of interleukin 1α seems to be the same synergistic activity formerly ascribed to hemopoietin 1.