Abstract
Natural and recombinant human interferon-α (IFN-α) and-γ (IFN-γ) exert differentiation-inducing and cytocidal effects in vitro on cells of the human myeloblastic leukemia cell line ML-2. These activities of IFNs are modulated by polymyxin B (PMB), a cyclic polycationic peptide antibiotic effective on Gram-negative bacilli. The modulating effect of PMB varies according to the species of IFN, namely, PMB enhances the activities of either natural IFN-γ or recombinant IFN-γ, while it inhibits the effects of either natural IFN-α or recombinant IFN-α. The cause of this variety in PMB effect on IFNs remains to be clarified.
