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Requirement for Stat4 in interleukin-12-mediated responses of natural killer and T cells
W E Thierfelder1, J M van Deursen, K Yamamoto
1Department of Biochemistry, St Jude Children's Research Hospital, Memphis, Tennessee 38105, USA.
Abstract:
Signal transducers and activators of transcription (STATs) are activated by tyrosine phosphorylation in response to cytokines and mediate many of their functional responses. Stat4 was initially cloned as a result of its homology with Stat1 (refs 4, 5) and is widely expressed, although it is only tyrosine-phosphorylated after stimulation of T cells with interleukin (IL)-12 (refs 6,7). IL-12 is required for the T-cell-independent induction of the cytokine interferon (IFN)-gamma, a key step in the initial suppression of bacterial and parasitic infections. IL-12 is also important for the development of a Th1 response, which is critical for effective host defence against intracellular pathogens. To determine the function of Stat4 and its role in IL-12 signalling, we have produced mice that lack Stat4 by gene targeting. The mice were viable and fertile, with no detectable defects in haematopoiesis. However, all IL-12 functions tested were disrupted, including the induction of IFN-gamma, mitogenesis, enhancement of natural killer cytolytic function and Th1 differentiation.
Insights
Stat4 is crucial for interleukin-12 (IL-12) signaling, mediating interferon-gamma (IFN-gamma) induction and Th1 differentiation. Mice lacking Stat4 show disrupted IL-12 functions, highlighting its essential role in immune responses.
Area of Science:
- Immunology
- Molecular Biology
- Genetics
Background:
- Signal transducers and activators of transcription (STATs) mediate cytokine responses.
- Stat4, homologous to Stat1, is widely expressed but activated by IL-12 in T cells.
- IL-12 is vital for IFN-gamma induction, Th1 responses, and defense against intracellular pathogens.
Purpose of the Study:
- To elucidate the function of Stat4.
- To determine Stat4's role in IL-12 signaling pathways.
- To investigate the in vivo consequences of Stat4 deficiency.
Main Methods:
- Gene targeting was employed to generate Stat4-deficient mice.
- Phenotypic analysis of Stat4 knockout mice was performed.
- Assessment of IL-12 mediated immune responses, including IFN-gamma induction and Th1 differentiation.
Main Results:
- Stat4-deficient mice were viable and fertile with normal hematopoiesis.
- All tested IL-12 functions were abolished in the absence of Stat4.
- Key disrupted functions included IFN-gamma induction, mitogenesis, NK cell activity, and Th1 differentiation.
Conclusions:
- Stat4 is essential for mediating the biological effects of IL-12.
- Stat4 plays a critical role in regulating innate and adaptive immune responses.
- Targeting Stat4 may impact immune modulation strategies.