Activation of STAT proteins and cytokine genes in human Th1 and Th2 cells generated in the absence of IL-12 and IL-4.
We have shown previously that human CD4+ 45RO- T cells could be primed for a Th2 phenotype independent of IL-4 if they were activated by anti-CD28 mAb plus IL-2. If additional TCR signals were provided, the cells differentiated toward Th1 independent of IL-12. Here we show that anti-CD28/IL-2-primed Th2 cells expressed high levels of activated STAT6, but no cytokine mRNA. Moreover, both Th1 and Th2 cells expressed active STAT1 and -3, but not STAT2, -4, and -5. Restimulation of Th1 or Th2 cells via CD3 plus CD28 induced production of IFN-gamma or IL-4, respectively, but did not alter the activation status/DNA binding activity of STATs. Addition of IL-4 (or anti-IL-4 mAb) to restimulated Th2 cells did not modulate STAT6 activation or IL-4 expression, confirming the full commitment. However, Th2 cells remained responsive to IL-12, which repressed STAT6 DNA binding but activated STAT4, and this coincided with a suppression of IL-4/IL-5 and an induction of IFN-gamma. In Th1 cells, IL-12 activated both STAT6 and STAT4, and IL-4 activated STAT6, but in both cases the Th1 phenotype remained. Together the data show that CD28/IL-2-dependent Th2 priming activated STAT6 without inducing IL-4 expression. The primed Th cells resembled memory cells and produced IL-4 upon the first CD3/CD28 costimulus without detectable modulation of STATs. Th2 cells remained responsive to IL-12, which repressed STAT6 DNA binding and activated STAT4, and switched the cells to Th1. The effects of IL-12 may depend on the commitment of the cells, since IL-12 phosphorylated STAT6 in Th1 and dephosphorylated STAT6 in Th2 cells.
Moriggl
R
R
Institute for Experimental Cancer Research, Tumor Biology Center, Freiburg, Germany.
Kristofic
C
C
Kinzel
B
B
Volarevic
S
S
Groner
B
B
Brinkmann
V
V
D002454:Cell Differentiation / Q000235:genetics / Q000276:immunology; D002478:Cells, Cultured; D016207:Cytokines / Q000235:genetics*; D004268:DNA-Binding Proteins / Q000378:metabolism*; D005786:Gene Expression Regulation / Q000187:drug effects / Q000276:immunology*; D006801:Humans; D018664:Interleukin-12 / Q000494:pharmacology / Q000502:physiology*; D015847:Interleukin-4 / Q000494:pharmacology / Q000502:physiology*; D008213:Lymphocyte Activation / Q000235:genetics; D050794:STAT1 Transcription Factor; D015398:Signal Transduction / Q000187:drug effects / Q000276:immunology; D018417:Th1 Cells / Q000276:immunology / Q000378:metabolism*; D018418:Th2 Cells / Q000276:immunology / Q000378:metabolism*; D015534:Trans-Activators / Q000378:metabolism*; D014158:Transcription, Genetic / Q000276:immunology
D016207:Cytokines; D004268:DNA-Binding Proteins; D050794:STAT1 Transcription Factor; C494079:STAT1 protein, human; D015534:Trans-Activators; D018664:Interleukin-12; D015847:Interleukin-4