In a significant advancement for autoimmune disease research, a novel interleukin-2 (IL-2) and transforming growth factor-beta (TGFβ) co-agonist has demonstrated remarkable efficacy in establishing immune tolerance and suppressing experimental autoimmune encephalomyelitis (EAE), a widely used mouse model of multiple sclerosis. This breakthrough, unveiled by Sun et al. in their recent publication in Nature, showcases the therapeutic potential of TGM1–IL-2, a fusion protein designed to synergistically engage IL-2 and TGFβ receptor pathways to induce peripheral regulatory T cells (pTreg). This engineered molecule not only facilitates the expansion of functional pTregs but also profoundly attenuates neuroinflammation and pathogenic T helper 17 (Th17) cell responses, suggesting a new horizon in autoimmune therapy development.
The study leverages the MOG_35–55-induced EAE model—which closely mimics human autoimmune neuroinflammation—to evaluate the immunomodulatory capabilities of TGM1–IL-2. Traditionally, therapeutic strategies targeting IL-2 or TGFβ alone have been hampered by limited efficacy or safety concerns due to systemic immunosuppression. However, this integrated approach capitalizes on the complementary immunoregulatory roles of IL-2 and TGFβ, aimed at selectively enhancing pTreg populations, which are critical for maintaining immune homeostasis and preventing aberrant autoimmune responses.
Detailed flow cytometric analyses revealed that treatment with TGM1–IL-2 robustly drives the differentiation of transferred MOG_35–55-specific 2D2 CD4^+ T cells into FOXP3^+ pTreg cells across multiple lymphoid compartments, including mesenteric lymph nodes (mLNs), inguinal lymph nodes (ILNs), and spleens. Notably, a significant subset of these pTregs co-expressed the lineage-defining transcription factor RORγt, indicative of their specialized phenotype. This dual transcriptional profile may reflect a unique state of regulatory T cells poised for potent immunosuppressive function, beyond classical FOXP3^+ Tregs.
Beyond phenotypic characterization, TGM1–IL-2-induced pTregs exhibited heightened expression of hallmark suppressive and activation markers such as CD25, ICOS, CTLA4, CD39, and IL-10. These molecules are instrumental in dampening autoreactive T cell responses, underscoring the functional competence of these induced pTregs. The induction of CD103 further suggests enhanced tissue retention capabilities, which may be crucial for their suppressive role in inflamed tissues like the central nervous system.
Crucially, the immunoregulatory impact translated into significant therapeutic protection. Mice pretreated with TGM1–IL-2 were largely protected from clinical EAE manifestations despite rechallenge with MOG_35–55 peptide emulsified in complete Freund’s adjuvant, a potent antigenic stimulus. Impressively, 9 out of 11 treated mice remained EAE-free, indicating durable tolerance induction. This profound clinical outcome positions TGM1–IL-2 as a promising candidate for long-lasting modulation of autoreactive immunity.
Further pathophysiological insights were obtained from analysis of immune cell infiltration in the spinal cord, a key site of neuroinflammation in EAE. TGM1–IL-2 treatment markedly reduced the infiltration of CD45.2^+ immune cells, including myeloid cells (CD11b^+CD3^−) and T cells (CD11b^−CD3^+), with a pronounced decrease specifically in CD4^+ T cells. This reduction in immune cell trafficking to the central nervous system likely contributes substantially to the observed attenuation of disease severity.
Moreover, the therapy specifically diminished the numbers of Th1 (IFNγ-producing) and Th17 (IL-17A-producing) CD4^+ T cells within the spinal cord, critical effector subsets implicated in EAE pathogenesis. Although the percentages of these cytokine-producing cells remained relatively stable, the absolute reduction in cell numbers underscores an overall suppression of neuroinflammatory responses. This selective inhibition of pathogenic T cell expansion is a key mechanistic insight into how TGM1–IL-2 mediates disease amelioration.
A particularly notable finding was the decreased frequency and absolute number of GM-CSF^+ CD4^+ T cells following treatment. GM-CSF-producing Th17 cells are recognized as pivotal drivers of CNS autoimmunity due to their role in recruiting and activating myeloid cells. The capacity of TGM1–IL-2 to curtail this critical pathogenic subset highlights the therapy’s targeted immunosuppressive profile, potentially offering advantages over broader immunosuppressive agents which may impair protective immunity.
The data also suggest that the novel IL-2-TGFβ surrogate agonist fosters a microenvironment conducive to immune regulation rather than indiscriminate immune suppression. By amplifying the regulatory arm of the immune system, the therapy restores balance and actively reprograms autoreactive T cells, offering a more physiological and nuanced approach to treating autoimmunity compared to conventional therapies.
From a translational perspective, these findings pave the way for novel biologics capable of inducing antigen-specific tolerance, a long-sought goal in the treatment of autoimmune diseases like multiple sclerosis. The preferential expansion of pTregs and modulation of pathogenic T cell subsets indicate potential applicability beyond neuroinflammation, possibly extending to other autoimmune conditions driven by dysregulated T cell responses.
Mechanistically, the design of TGM1–IL-2 as a co-agonist targeting both IL-2R and TGFβR represents an elegant solution to previous challenges in cytokine therapy, harnessing complementary receptor pathways for synergistic immunomodulation. This paradigm may inspire the development of similar bifunctional therapeutics tailored to complex immune disorders.
In summary, the study by Sun et al. underscores the promise of biologically engineered cytokine agonists in rewiring the immune system to favor tolerance and prevent autoimmunity. The robust induction of FOXP3^+RORγt^+ pTregs, attenuation of CNS inflammation, and clinical protection in EAE collectively support the therapeutic potential of TGM1–IL-2. Future investigations will be crucial to evaluate long-term safety, dosing strategies, and efficacy in humanized models or clinical trials.
As autoimmune diseases continue to pose significant clinical challenges, innovations like TGM1–IL-2 that precisely recalibrate immune responses offer hope for more effective and safer treatment options. The intersection of cytokine biology, synthetic protein engineering, and immunotherapy heralds a new era in the quest to tame autoimmunity through immune tolerance.
This groundbreaking research not only broadens our understanding of immune regulation but also exemplifies how tailored biological surrogates can transform therapeutic landscapes. The journey from bench to bedside will determine the full impact of these findings, yet the groundwork laid herein clearly shines a light on the future possibilities for immune intervention.
Subject of Research: Immune tolerance induction and suppression of autoimmune neuroinflammation using an IL-2–TGFβ co-agonist in a murine model of experimental autoimmune encephalomyelitis (EAE).
Article Title: Facile induction of immune tolerance by an interleukin-2–TGFβ surrogate agonist.
Article References:
Sun, Q., Barrett, A.K., Ogishi, M. et al. Facile induction of immune tolerance by an interleukin-2–TGFβ surrogate agonist. Nature (2026). https://doi.org/10.1038/s41586-026-10208-0
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