NO is a free radical with pleiotropic functions. We have shown earlier that NO induces a population of CD4+CD25+Foxp3− regulatory T cells (NO-Tregs) that suppress the functions of CD4+CD25− effector T cells in vitro and in vivo. We report in this study an unexpected finding that NO-Tregs suppressed Th17 but not Th1 cell differentiation and function. In contrast, natural Tregs (nTregs), which suppressed Th1 cells, failed to suppress Th17 cells. Consistent with this observation, NO-Tregs inhibited the expression of retinoic acid–related orphan receptor γt but not T-bet, whereas nTregs suppressed T-bet but not retinoic acid–related orphan receptor γt expression. The NO-Treg–mediated suppression of Th17 was partially cell contact–dependent and was associated with IL-10. In vivo, adoptively transferred NO-Tregs potently attenuated experimental autoimmune encephalomyelitis. The disease suppression was accompanied by a reduction of Th17, but not Th1 cells in the draining lymph nodes, and a decrease in the production of IL-17, but an increase in IL-10 synthesis. Our results therefore demonstrate the differential suppressive function between NO-Tregs and nTregs and indicate specialization of the regulatory mechanism of the immune system.
This work was supported by the Wellcome Trust, the Medical Research Council (United Kingdom), the European Union, and the Highly Cited Grant of the King Abdulaziz University, Saudi Arabia.
The online version of this article contains supplemental material.
- Received September 13, 2012.
- Accepted April 26, 2013.
- Copyright © 2013 by The American Association of Immunologists, Inc.