Abstract
Highly purified interferon-α and -β (IFN-α, -β) are ineffective in induction of differentiation of human myeloid leukemia cell lines, ML-1 and HL-60. On the other hand highly purified natural interferon-γ (IFN-γ) induced differentiation having characteristics that are associated with the human promyelocytic leukemia cell line, HL-60. Monoclonal antibody to IFN-γ neutralized its activity. However, the natural IFN-γhad almost no inducing activity in ML-1, a human myeloblastic leukemia cell line. Similar results were obtained using recombinant IFN-γ. Mitogen stimulated human leukocyte conditioned medium (LCM) induced differentiation of both ML-1 and HL-60 cells. After treatment of LCM with monoclonal antibody to IFN-γ, LCM activity was reduced more than 50% in ML-1 cells, and 80% in HL-60 cells. Even if IFN-γ was eliminated from LCM by affinity chromatography, the LCM induced differentiation of ML-1 and HL-60 cells, but IFN-γ markedly enhanced the ML-1 cell differentiation induced by IFN-γ free LCM. The results suggest that leukocytes produce differentiation inducing factor (s) other than IFN-γ, and that IFN-γ is both an inducer and an enhancer of induction of human myelogenous leukemia cells.
