Regulatory T cells (Tregs) promote immune homeostasis by maintaining self-tolerance and regulating inflammatory responses. Under certain inflammatory conditions, Tregs can lose their lineage stability and function. Previous studies have reported that ex vivo exposure to retinoic acid (RA) enhances Treg function and stability. However, it is unknown how RA receptor signaling in Tregs influences these processes in vivo. Herein, we employed mouse models in which RA signaling is silenced by the expression of the dominant negative receptor (DN) RARα in all T cells. Despite the fact that DNRARα conventional T cells are hypofunctional, Tregs had increased CD25 expression, STAT5 pathway activation, mTORC1 signaling and supersuppressor function. Furthermore, DNRARα Tregs had increased inhibitory molecule expression, amino acid transporter expression, and metabolic fitness and decreased antiapoptotic proteins. Supersuppressor function was observed when wild-type mice were treated with a pharmacologic pan-RAR antagonist. Unexpectedly, Treg-specific expression of DNRARα resulted in distinct phenotypes, such that a single allele of DNRARα in Tregs heightened their suppressive function, and biallelic expression led to loss of suppression and autoimmunity. The loss of Treg function was not cell intrinsic, as Tregs that developed in a noninflammatory milieu in chimeric mice reconstituted with DNRARα and wild-type bone marrow maintained the enhanced suppressive capacity. Fate mapping suggested that maintaining Treg stability in an inflammatory milieu requires RA signaling. Our findings indicate that RA signaling acts as a rheostat to balance Treg function in inflammatory and noninflammatory conditions in a dose-dependent manner.
Bibliographical noteFunding Information:
BB receives remuneration as an advisor to Kamon Pharmaceuticals, Five Prime Therapeutics, Regeneron Pharmaceuticals, Magenta Therapeutics, and BlueRock Therapeuetics; research support from Fate Therapeutics, RXi Pharmaceuticals, Alpine Immune Sciences, Abbvie, the Leukemia and Lymphoma Society, the Children’s Cancer Research Fund, and the KidsFirst Fund and is a cofounder of Tmunity. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.
We thank Brent Koehn and Nicole Chapman for critical reading of the manuscript, Jamie Panthera for excellent animal husbandry, and Ron Mc Elmurry, Christopher Less, Juan E. Abrahante Lloréns, and the UMN genomics center for technical assistance. This work was supported by grants from the National Institutes of Health, National Institute of Allergy and Infectious Diseases P01 AI056299, R37 AI034495 (BRB), and R01 AI091627 (IM) and the National Heart, Lung, and Blood Institute R01 HL56067 (BRB). This work was supported in part using the resources of the Center for Innovative Technology at Vanderbilt University. GT was supported by a Canadian Institutes of Health Research (CIHR) fellowship. Figures were created with Biorender.com.
© 2022, The Author(s), under exclusive licence to CSI and USTC.
- Retinoic acid
- Tregulatory cells
- Signal Transduction
- Immune Tolerance
- T-Lymphocytes, Regulatory
PubMed: MeSH publication types
- Journal Article
- Research Support, Non-U.S. Gov't
- Research Support, N.I.H., Extramural