IL-12, but not IFN-alpha, promotes STAT4 activation and Th1 development in murine CD4+ T cells expressing a chimeric murine/human Stat2 gene.
Humans and mice have evolved distinct pathways for Th1 cell development. Although IL-12 promotes CD4(+) Th1 development in both murine and human T cells, IFN-alphabeta drives Th1 development only in human cells. This IFN-alphabeta-dependent pathway is not conserved in the mouse species due in part to a specific mutation within murine Stat2. Restoration of this pathway in murine T cells would provide the opportunity to more closely model specific human disease states that rely on CD4(+) T cell responses to IFN-alphabeta. To this end, the C terminus of murine Stat2, harboring the mutation, was replaced with the corresponding human Stat2 sequence by a knockin targeting strategy within murine embryonic stem cells. Chimeric m/h Stat2 knockin mice were healthy, bred normally, and exhibited a normal lymphoid compartment. Furthermore, the murine/human STAT2 protein was expressed in murine CD4(+) T cells and was activated by murine IFN-alpha signaling. However, the murine/human STAT2 protein was insufficient to restore full IFN-alpha-driven Th1 development as defined by IFN-gamma expression. Furthermore, IL-12, but not IFN-alpha, promoted acute IFN-gamma secretion in collaboration with IL-18 stimulation in both CD4(+) and CD8(+) T cells. The inability of T cells to commit to Th1 development correlated with the lack of STAT4 phosphorylation in response to IFN-alpha. This finding suggests that, although the C terminus of human STAT2 is required for STAT4 recruitment and activation by the human type I IFNAR (IFN-alphabetaR), it is not sufficient to restore this process through the murine IFNAR complex.
Persky
Meredith E
ME
Center for Immunology and Department of Molecular Biology, University of Texas Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, TX 75390, USA.
Murphy
Kenneth M
KM
Farrar
J David
JD
D000818:Animals; D015153:Blotting, Western; D002478:Cells, Cultured; D002678:Chimera; D004268:DNA-Binding Proteins / Q000235:genetics* / Q000276:immunology / Q000378:metabolism*; D004797:Enzyme-Linked Immunosorbent Assay; D006801:Humans; D047468:Immunoprecipitation; D016898:Interferon-alpha / Q000276:immunology; D018664:Interleukin-12 / Q000276:immunology* / Q000378:metabolism; D008213:Lymphocyte Activation / Q000276:immunology; D008565:Membrane Proteins; D051379:Mice; D053633:Receptor, Interferon alpha-beta; D017471:Receptors, Interferon / Q000276:immunology / Q000378:metabolism; D050795:STAT2 Transcription Factor; D050797:STAT4 Transcription Factor; D018417:Th1 Cells / Q000166:cytology / Q000276:immunology*; D015534:Trans-Activators / Q000235:genetics* / Q000276:immunology / Q000378:metabolism*
D004268:DNA-Binding Proteins; C507964:IFNAR1 protein, human; D016898:Interferon-alpha; D008565:Membrane Proteins; D017471:Receptors, Interferon; D050795:STAT2 Transcription Factor; C494084:STAT2 protein, human; D050797:STAT4 Transcription Factor; C494090:STAT4 protein, human; C494085:Stat2 protein, mouse; C494091:Stat4 protein, mouse; D015534:Trans-Activators; D053633:Receptor, Interferon alpha-beta; D018664:Interleukin-12