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IL-10 is essential to maintain intestinal homeostasis. CD4+ T regulatory type 1 (TR1) cells produce large amounts of this cytokine and are therefore currently being examined in clinical trials as T cell therapy in patients with inflammatory bowel disease. However, factors and molecular signals sustaining TR1 cell regulatory activity still need to be identified to optimize the efficiency and ensure the safety of these trials. We investigated the role of IL-10 signaling in mature TR1 cells in vivo. Double IL-10eGFP Foxp3mRFP reporter mice and transgenic mice with impairment in IL-10 receptor signaling were used to test the activity of TR1 cells in a murine inflammatory bowel disease model, a model that resembles the trials performed in humans. The molecular signaling was elucidated in vitro. Finally, we used human TR1 cells, currently employed for cell therapy, to confirm our results. We found that murine TR1 cells expressed functional IL-10Ra. TR1 cells with impaired IL-10 receptor signaling lost their regulatory activity in vivo. TR1 cells required IL-10 receptor signaling to activate p38 MAPK, thereby sustaining IL-10 production, which ultimately mediated their suppressive activity. Finally, we confirmed these data using human TR1 cells. In conclusion, TR1 cell regulatory activity is dependent on IL-10 receptor signaling. These data suggest that to optimize TR1 cell-based therapy, IL-10 receptor expression has to be taken into consideration. [ABSTRACT FROM AUTHOR]

T regulatory type 1 (Tr1) cells, which are defined by their regulatory function, lack of Foxp3, and high expression of IL-10, CD49b, and LAG-3, are known to be able to suppress Th1 and Th17 in the intestine. Th1 and Th17 cells are also the main drivers of crescentic glomerulonephritis (GN), the most severe form of renal autoimmune disease. However, whether Tr1 cells emerge in renal inflammation and, moreover, whether they exhibit regulatory function during GN have not been thoroughly investigated yet. To address these questions, we used a mouse model of experimental crescentic GN and double Foxp3mRFP IL-10eGFP reporter mice. We found that Foxp3neg IL-10-producing CD4+ T cells infiltrate the kidneys during GN progression. Using single-cell RNA sequencing, we could show that these cells express the core transcriptional factors characteristic of Tr1 cells. In line with this, Tr1 cells showed a strong suppressive activity ex vivo and were protective in experimental crescentic GN in vivo. Finally, we could also identify Tr1 cells in the kidneys of patients with antineutrophil cytoplasmic autoantibody-associated GN and define their transcriptional profile. Tr1 cells are currently used in several immune-mediated inflammatory diseases, such as T-cell therapy. Thus, our study provides proof of concept for Tr1 cell-based therapies in experimental GN., (Copyright © 2023 by The American Association of Immunologists, Inc.)

IL-10 is essential to maintain intestinal homeostasis. CD4 + T regulatory type 1 (T R 1) cells produce large amounts of this cytokine and are therefore currently being examined in clinical trials as T cell therapy in patients with inflammatory bowel disease. However, factors and molecular signals sustaining T R 1 cell regulatory activity still need to be identified to optimize the efficiency and ensure the safety of these trials. We investigated the role of IL-10 signaling in mature T R 1 cells in vivo. Double IL-10 eGFP Foxp3 mRFP reporter mice and transgenic mice with impairment in IL-10 receptor signaling were used to test the activity of T R 1 cells in a murine inflammatory bowel disease model, a model that resembles the trials performed in humans. The molecular signaling was elucidated in vitro. Finally, we used human T R 1 cells, currently employed for cell therapy, to confirm our results. We found that murine T R 1 cells expressed functional IL-10Rα. T R 1 cells with impaired IL-10 receptor signaling lost their regulatory activity in vivo. T R 1 cells required IL-10 receptor signaling to activate p38 MAPK, thereby sustaining IL-10 production, which ultimately mediated their suppressive activity. Finally, we confirmed these data using human T R 1 cells. In conclusion, T R 1 cell regulatory activity is dependent on IL-10 receptor signaling. These data suggest that to optimize T R 1 cell-based therapy, IL-10 receptor expression has to be taken into consideration., Competing Interests: The authors have declared that there is no conflict of interest., (Copyright © 2017 by The American Association of Immunologists, Inc.)