Frontline: absence of functional STAT4 activation despite detectable tyrosine phosphorylation induced by murine IFN-alpha.
We previously reported that IL-12, but not IFN-alphaA/D, induces T helper type (Th) 1 development and STAT4 phosphorylation in murine CD4+ T cells. However, a recent study reported that IFN-alphaA/D and recombinant murine IFN-alphaA can induce STAT4 phosphorylation, although more weakly than IL-12, largely in CD8+ rather than CD4+ T cells. That report did not examine Th1 development or directly demonstrate induction of IFN-gamma by IFN-alpha. To address these differences, we compared IFN-alphaA/D, murine IFN-alphaA, and IL-12 for STAT4 phosphorylation, formation of active nuclear DNA binding complexes, induction of Th1 development, and production of IFN-gamma in murine CD4+ T cells. IFN-alphaA induced detectable STAT4 phosphorylation, although at significantly lower levels than induced by IL-12. Furthermore, in contrast to IL-12, IFN-alphaA failed to induce Th1 development or the formation of DNA binding complexes or to synergize with IL-18 for induction of IFN-gamma production. STAT1-deficient CD4+ T cells showed increased IFN-alphaA-induced STAT4 phosphorylation but still exhibited significantly lower amounts of cytokine-induced IFN-gamma compared to IL-12. In summary, these results suggest that in contrast to IL-12, IFN-alphaA does not play a functionally significant role in meditating the STAT4-dependent induction of Th1 development or IFN-gamma production in CD4+ T cells.
Department of Pathology and Center for Immunology, Washington University School of Medicine, St. Louis, MO 63110, USA.
Lisa S
LS
Berenson
J David
JD
Farrar
Theresa L
TL
Murphy
Kenneth M
KM
Murphy
D000818:Animals; D000938:Antigen-Presenting Cells / Q000502:physiology; D004268:DNA-Binding Proteins / Q000502:physiology*; D016898:Interferon-alpha / Q000494:pharmacology*; D007371:Interferon-gamma / Q000096:biosynthesis; D018664:Interleukin-12 / Q000494:pharmacology; D020382:Interleukin-18 / Q000494:pharmacology; D051379:Mice; D008807:Mice, Inbred BALB C; D010766:Phosphorylation; D050797:STAT4 Transcription Factor; D018417:Th1 Cells / Q000502:physiology; D015534:Trans-Activators / Q000502:physiology*; D014443:Tyrosine / Q000378:metabolism*
D004268:DNA-Binding Proteins; D016898:Interferon-alpha; D020382:Interleukin-18; D050797:STAT4 Transcription Factor; C494091:Stat4 protein, mouse; D015534:Trans-Activators; D018664:Interleukin-12; D014443:Tyrosine; D007371:Interferon-gamma