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In Vitro Assay to Evaluate the Impact of Immunoregulatory Pathways on HIV-specific CD4 T Cell Effector Function
Published on: October 15, 2013
STAT5 interferes with PD-1 transcriptional activation and affects CD8+ T-cell sensitivity to PD-1-dependent
Guanning Wang1, Masaki Tajima1, Tasuku Honjo2
1Department of Immunology, Foundation for Biomedical Research and Innovation at Kobe, Kobe 650-0047, Japan.
Abstract:
Programmed cell death-1 (PD-1) is a co-inhibitory receptor that dampens immune responses upon interaction with PD-L1 and PD-L2. Although PD-1 expression on T cells is known to be activation-dependent, how cytokines modify its regulation is not fully resolved. Using polyclonal T-cell activation to study cytokine-dependent PD-1 regulation, we found that IL-2 inhibited transcriptional up-regulation of PD-1 despite the promotion of T-cell activation. The IL-2-mediated reduction in PD-1 expression augmented CD8+ T-cell activities against PD-L1-expressing target cells. To study the mechanism of PD-1 reduction, we focused on STAT5 activation in the IL-2 signaling pathway. Bioinformatic analysis suggested a novel conserved PD-1 promoter domain where NFAT and STAT5 can potentially compete with each other for binding. NFAT1 interaction with this domain revealed substantial potency in PD-1 transcription compared to STAT5A, and STAT5A overexpression could quench NFAT1-dependent PD-1 up-regulation in a sequence-specific manner. Chromatin immunoprecipitation analysis of activated T cells showed that IL-2 treatment significantly diminished the binding of NFAT1 and NFAT2 in the hypothesized competition site, while STAT5 binding to the same region was increased. These results raise the possibility that the competition of transcriptional factors might be involved in the fine-tuning of PD-1 expression by cytokines such as IL-2.
Insights
Interleukin-2 (IL-2) reduces Programmed Cell Death-1 (PD-1) expression on T cells by influencing transcription factors. This reduction enhances CD8+ T-cell anti-tumor activity.
Area of Science:
- Immunology
- Molecular Biology
- Cell Signaling
Background:
- Programmed Cell Death-1 (PD-1) is a crucial co-inhibitory receptor that regulates T-cell immune responses.
- PD-1 expression on T cells is generally activation-dependent, but the precise role of cytokines in its regulation remains incompletely understood.
- Understanding cytokine-mediated regulation of PD-1 is vital for optimizing T-cell-based immunotherapies.
Purpose of the Study:
- To investigate the effect of Interleukin-2 (IL-2) on the regulation of Programmed Cell Death-1 (PD-1) expression in T cells.
- To elucidate the molecular mechanisms underlying IL-2-mediated modulation of PD-1 transcription.
- To assess the functional consequences of altered PD-1 expression on CD8+ T-cell activity.
Main Methods:
- Polyclonal T-cell activation models were employed to study cytokine-dependent PD-1 regulation.
- Bioinformatic analysis identified a conserved PD-1 promoter domain potentially involving NFAT and STAT5 transcription factors.
- Chromatin immunoprecipitation (ChIP) assays were used to analyze the binding of NFAT and STAT5 to the PD-1 promoter in activated T cells.
Main Results:
- IL-2 significantly inhibited the transcriptional up-regulation of PD-1, even while promoting T-cell activation.
- IL-2 treatment led to decreased binding of NFAT1 and NFAT2, and increased binding of STAT5 to a specific PD-1 promoter region.
- Overexpression of STAT5A demonstrated the ability to suppress NFAT1-driven PD-1 up-regulation in a sequence-specific manner.
Conclusions:
- IL-2 reduces PD-1 expression on T cells, thereby enhancing CD8+ T-cell activity against PD-L1-expressing targets.
- A competitive binding mechanism between NFAT and STAT5 transcription factors at the PD-1 promoter is proposed to mediate IL-2's regulatory effect.
- Cytokine-driven competition among transcriptional factors offers a potential mechanism for fine-tuning PD-1 expression and immune responses.
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