Retinoic Acid Induces Functionally Suppressive Foxp3+RORγt+ T Cells In Vitro

Introduction: CD4(+) T cells with regulatory function co-expressing Foxp3 and ROR gamma t are linked to the development of oral tolerance towards innocuous food antigens in mice. This study aimed to discern the role played by IL-6 and retinoic acid (RA) in the in vitro generation of Foxp3(+)ROR gamma t(+) T cells and to investigate whether such cells have suppressive properties. Methods: CD4(+)CD25(-) T cells isolated from the spleen of BALB/c mice, were stimulated in the presence of IL-2 alone or together with TFG-beta and different concentrations of IL-6 and/or RA. Percentage of Foxp3(+), ROR gamma t(+), IL-17(+), Foxp3(+)ROR gamma t(-), Foxp3(+)ROR gamma t(+), and Foxp3(-)ROR gamma t(+) T cells within the total CD4(+) T cell population, production of cytokines (IL-10 and IL-17A) and gene expression (Foxp3, Rorc, Tgfb1, Il6, Il10, and Il17) were assessed at different time points. The phenotype and ability of cells generated from CD4(+)CD44(-)CD62L(+) cells in the presence of RA to suppress effector T cell proliferation was assessed. Results: TGF-beta plus IL-6 induced the generation of Foxp3(+) and double positive Foxp3(+)ROR gamma t(+) T cells to a higher extent than TGF-beta alone at the beginning of the incubation period, although expression of Foxp3 subsequently declined. RA, added to TGF-beta, increased Foxp3 and Rorc expression and Foxp3 and ROR gamma t transcription and promoted the differentiation of Foxp3(+)ROR gamma t(-) and Foxp3(+)ROR gamma t(+) cells that expressed and secreted IL-17. Foxp3(+) T cells generated in vitro in presence of RA were functionally suppressive. Conclusions: Under the influence of IL-2 and TGF-beta, suppressive Foxp3(+)ROR gamma t(+) T cells that express and secrete IL-17 can be produced in vitro and RA further contributes to stabilize this phenotype.

Automated summary

The study demonstrated that under the influence of IL-2 and TGF-beta, IL-6 can induce the generation of Foxp3(+) and double positive Foxp3(+)ROR gamma t(+) T cells. Furthermore, the presence of RA helps to stabilize the phenotype of these cells and promote the suppressive function of Foxp3(+) T cells.