INTERFERON-ALPHA ACTIVATES SIGNAL TRANSDUCERS AND ACTIVATORS OF TRANSCRIPTION-5 AND TRANSCRIPTION-6 IN DAUDI CELLS

In most cells studied so far, interferon-alpha (IFN-alpha) activates s ignal transducer and activator of transcription (Stat1), Stat2 and Sta t3, whereas interferon-gamma (IFN-gamma) induces Stat1 only. In genera l, each of the several dozens of cytokines, growth factors and hormone s that signal through the Janus kinases-signal transducers and activat ors of transcription (Jak-STAT) pathway activates a distinct subset of STATs, and this selectivity is thought to be essential for the specif icity of the cellular responses toward these ligands. Here, we have st udied the pattern of STAT activation in the human lymphoblastoid cell line Daudi in response to IFN-alpha. In addition to Stat1, Stat2 and S tat3 activation, IFN-alpha was found to directly induce activation of Stat5 and Stat6. Cell-type-specific activation of additional STATs cou ld be responsible for cell-type-specific responses to IFN-alpha.