Effect of interferon-alpha on neutrophil functions.

Incubation of neutrophils with interferon-alpha (IFN-alpha) for 5 min and subsequent stimulation with the calcium ionophore A23187 enhanced the production of oxygen radicals, while a suppression was obtained with FMLP-stimulated cells. Similar data were observed for the direct G-protein activator sodium fluoride (NaF). Incubation of the cells with IFN-alpha and subsequent stimulation with FMLP (in the presence of cytochalasin b) reduced the generation of the chemotactic active leukotriene B4 (LTB4). The metabolism of LTB4 was significantly inhibited. IFN-alpha decreased the specific binding sites for LTB4 and increased the number of binding sites for FMLP. The GTPase activity as a parameter for the activation of G-proteins was enhanced by IFN-alpha. Preincubation of the cells with IFN-alpha and subsequent stimulation with NaF increased the GTPase activity synergistically, whereas co-incubation of IFN-alpha with FMLP showed additive effects. Our results clearly demonstrate the modulatory effects of IFN-alpha on granulocyte functions with regard to the receptor-mediated signal transduction.