Distinct Characteristics of Murine Stat4 Activation in Response to Il-12 and Ifn-

Berenson, L.S.; Gavrieli, M.; Farrar, J.D.; Murphy, T.L.; Murphy, K.M.

The Journal of Immunology 177(8): 5195-5203

2006


DOI: 10.4049/jimmunol.177.8.5195
Accession: 068490387

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Abstract
The role of type I IFN in Th1 development, STAT4 activation, and IFN-gamma production in murine T cells has remained unresolved despite extensive examination. Initial studies indicated that IFN-alpha induced Th1 development and IFN-gamma production in human, but not murine, T cells, suggesting species-specific differences in signaling. Later studies suggested that IFN-alpha also induced Th1 development in mice, similar to IL-12. More recent studies have questioned whether IFN-alpha actually induces Th1 development even in the human system. In the present study, we compared the capacity of IL-12 and IFN-alpha to induce Th1 differentiation, STAT4 phosphorylation, and IFN-gamma production in murine T cells. First, we show that IFN-alpha, in contrast to IL-12, cannot induce Th1 development. However, in differentiated Th1 cells, IFN-alpha can induce transient, but not sustained, STAT4 phosphorylation and, in synergy with IL-18, can induce transient, but not sustained, IFN-gamma production in Th1 cells, in contrast to the sustained actions of IL-12. Furthermore, loss of STAT1 increases IFN-alpha-induced STAT4 phosphorylation, but does not generate levels of STAT4 activation or IFN-gamma production achieved by IL-12 or convert transient STAT4 activation into a sustained response. Our findings agree with recent observations in human T cells that IFN-alpha-induced STAT4 activation is transient and unable to induce Th1 development, and indicate that IFN-alpha may act similarly in human and murine T cells.