Antigen receptor-engineered Tregs inhibit CNS autoimmunity in cell therapy using non-redundant immune mechanisms in mice

CD4(+) FOXP3(+) T regulatory cells (Tregs) are currently explored to develop cell therapies against immune-mediated disorders, with an increasing focus on antigen receptor-engineered Tregs. Deciphering their mode of action is necessary to identify the strengths and limits of this approach. Here, we addressed this issue in an autoimmune disease of the central nervous system (CNS), experimental autoimmune encephalomyelitis (EAE). Following disease induction, autoreactive Tregs up-regulated LAG-3 and CTLA-4 in lymph nodes, while interleukin-10 (IL-10) and amphiregulin (AREG) were increased in CNS Tregs. Using genetic approaches, we demonstrated that IL-10, CTLA-4, and LAG-3 were non-redundantly required for the protective function of antigen receptor-engineered Tregs against EAE in cell therapy whereas AREG was dispensable. Treg-derived IL-10 and CTLA-4 were both required to suppress acute autoreactive CD4(+) T cell activation, which correlated with disease control. These molecules also affected the accumulation in the recipients of engineered Tregs themselves, underlying complex roles for these molecules. Noteworthy, despite the persistence of the transferred Tregs and their protective effect, autoreactive T cells eventually accumulated in the spleen of treated mice. In conclusion, this study highlights the remarkable power of antigen receptor-engineered Tregs to appropriately provide multiple suppressive factors non-redundantly necessary to prevent autoimmune attacks