Modification of the FoxP3 Transcription Factor Principally Affects Inducible T Regulatory Cells in a Model of Experimental Autoimmune Encephalomyelitis

Abstract

T regulatory (Treg) cells expressing the transcription factor FoxP3 play a key role in protection against autoimmune disease. GFP-FoxP3 reporter mice have been used widely to study the induction, function and stability of both thymically- and peripherally-induced Treg cells. The N-terminal modification of FoxP3, however, affects its interaction with transcriptional co-factors; this can alter Treg cell development and function in certain self-antigen specific animal models. Interestingly, Treg cell function can be negatively or positively affected, depending on the nature of the model. In this study, we focused on the effect of the GFP-FoxP3 reporter on Treg cell development and function in the Tg4 mouse model. In this model, T cells express a transgenic T cell receptor (TCR) specific for the Myelin Basic Protein (MBP) peptide Ac1-9, making the animals susceptible to experimental autoimmune encephalomyelitis (EAE), a disease akin to multiple sclerosis in humans. Unlike diabetes-susceptible mice, Tg4 FoxP3gfp mice did not develop spontaneous autoimmune disease and did not demonstrate augmented susceptibility to induced disease. Concurrently, thymic generation of natural Treg cells was not negatively affected. The induction of FoxP3 expression in naive peripheral T cells was, however, significantly impaired as a result of the transgene. This study shows that the requirements for the interaction of FoxP3 with co-factors, which governs its regulatory ability, differ not only between natural and inducible Treg cells but also between animal models of diseases such as diabetes and EAE.

Extra‐thymically induced T regulatory cell subsets: the optimal target for antigen‐specific immunotherapy

“…This is in line with the finding that T cells of high antigen affinity are more readily converted into Foxp3 + Treg cells compared with T cells that recognize the same antigen with lower affinity . In our own studies of the efficacy of IL‐10 Treg cell and Foxp3 + i Treg cell differentiation and their suppressive function in vivo , we revealed a direct correlation between MHC II affinity of variants of the immunodominant myelin basic protein peptide Ac1‐9 and IL‐10 Treg cell formation, but were able to generate functional Foxp3 + i Treg cells using the lower affinity variant, in vitro . However, although subcutaneous administration of the low‐affinity peptide variant alone promotes the development of Foxp3 + p Treg cells in vivo , we have yet to achieve protection from CNS autoimmune disease with this approach (J. Verhagen, unpublished observation).…”

“…The p Treg cells have also been reported to develop in response to chronic inflammation resulting from asthma, autoimmune disease or infection and therefore appear to play a role in limiting the tissue damage that inevitably results from long‐lasting inflammation, although these findings are not universally supported (as reviewed thoroughly by Bilate and Lafaille). Interestingly, comparison of various animal models of autoimmune disease, each carrying the same modified version of Foxp3 protein that affects the development of p Treg cells but not t Treg cells, suggests that p Treg cells play a pivotal role in preventing the onset of type 1 diabetes but not arthritis or autoimmune encephalomyelitis . Disease‐specific conditions therefore seem to play an important role in the functionality of p Treg cells.…”

“…In vitro differentiation of Foxp3 + i Treg cells at very high purity (> 90%) can be achieved by activating naive CD4 + T cells with anti‐CD3 and anti‐CD28 in the presence of transforming growth factor‐ β and high doses of IL‐2 . Differentiation of i Treg cells using antigen and antigen‐presenting cells, however, typically does not give rise to a population more than 75% Foxp3 + , even if using naive TCR‐transgenic CD4 + T cells . Several agents have now been demonstrated to augment Foxp3 expression and improve in vivo functionality upon adoptive transfer of i Treg cells.…”

“…Interestingly, comparison of various animal models of autoimmune disease, each carrying the same modified version of Foxp3 protein that affects the development of p Treg cells but not t Treg cells, suggests that p Treg cells play a pivotal role in preventing the onset of type 1 diabetes but not arthritis or autoimmune encephalomyelitis. [26][27][28] Disease-specific conditions therefore seem to play an important role in the functionality of p Treg cells.…”

“…3 Differentiation of i Treg cells using antigen and antigen-presenting cells, however, typically does not give rise to a population more than 75% Foxp3 + , even if using naive TCR-transgenic CD4 + T cells. 28 Several agents have now been demonstrated to augment Foxp3 expression and improve in vivo functionality upon adoptive transfer of i Treg cells. As expected from its natural role in the gut, all-trans retinoic acid was shown to promote iTreg cell differentiation.…”