Long-lived memory CD8+ T cells are essential for the control of persistent viral infections. The mechanisms that preserve memory cells are poorly understood. Fate mapping of the transcriptional repressor GFI1 identified that GFI1 was differentially regulated in virus-specific CD8+ T cells and was selectively expressed in stem cell memory and central memory cells. Deletion of GFI1 led to reduced proliferation and progressive loss of memory T cells, which in turn resulted in failure to maintain antigen-specific CD8+ T cell populations following infection with chronic lymphocytic choriomeningitis virus or murine cytomegalovirus. Ablation of GFI1 resulted in downregulation of the transcription factors EOMES and BCL-2 in memory CD8+ T cells. Ectopic expression of EOMES rescued the expression of BCL-2, but the persistence of memory CD8+ T cells was only partially rescued. These findings highlight the critical role of GFI1 in the long-term maintenance of memory CD8+ T cells in persistent infections by sustaining their proliferative potential.
© 2025. Crown.

The administration of recombinant interleukin 2 (IL-2) in oncology is frequently hampered by dose-limiting toxicities, including potentially lethal vascular leak syndrome. Antibody-IL-2 fusion proteins capable of preferential tumor localization have shown encouraging signs of activity in clinical trials; however, they typically cause side effects shortly after intravenous administration, which may limit escalation to curative doses. There is an urgent need to engineer IL-2 products with "activity-on-demand" able to mask on-target off-tumor IL-2 activity without compromising therapeutic efficacy.
To design IL-2 biopharmaceuticals with "activity-on-demand", which would be non-toxic on administration but regain activity at the tumor site, we explored the therapeutic potential of the co-administration of signaling inhibitors with matched pharmacokinetic properties. In this work, we used the tumor-homing F8-IL2 fusion protein, specific to a splice variant of fibronectin, and masked off-tumor toxicity by co-administration of upadacitinib, which rapidly clears from circulation. Vascular leak syndrome was monitored by histopathological analysis, the extent of peripheral edema, and cytokine levels. Immune profiling of the tumors and secondary lymphoid organs was performed by flow cytometry.
In immunocompetent tumor-bearing mice, the combinatorial treatment significantly improved tolerability without any detectable loss of therapeutic activity, protecting the mice from body weight loss, uncontrolled systemic cytokine release, and severe vascular leak syndrome manifestations, including peripheral edema. F8-IL2 efficiently controlled tumor growth and retained its immunological activity within the neoplastic mass, as evidenced by the massive natural killer and cytotoxic T-cell infiltrates.
This study suggests that combinatorial treatments enable the administration of potentially curative doses of targeted IL-2 products while sparing healthy organs from life-threatening toxicities.
© Author(s) (or their employer(s)) 2025. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ Group.

We have previously shown that immune checkpoint receptors, including PD-1, are upregulated on T cells at the time of their activation, and that blockade of these receptors can improve the efficacy of antitumor vaccines. In the present study, we sought to determine whether, and by what mechanisms, the timing of PD-1 blockade with respect to vaccination affects antitumor T cell function.
TRAMP-C1 or E.G7-OVA tumor-bearing mice received PD-1 blockade at different timing intervals with a tumor-associated antigen vaccine. Tumor growth, survival, and immune-infiltrating populations were assessed. In vitro models of T cell activation using OT-I T cells and PD-(L)1 axis disruption with a PD-1 blocking antibody or PD-L1KO dendritic cells were used.
Mice receiving PD-1 blockade at the time of T cell activation with vaccine had better antitumor outcomes in comparison to mice receiving PD-1 blockade before or after immunization. T cells activated in vitro in the presence of PD-(L)1 axis disruption had a more differentiated, functional phenotype with decreased CD28 and CCR7 expression and increased production of the Tc1 cytokines IL-2, TNFα, and IFNγ. Intriguingly, a small subset of undifferentiated cells (CD28+) was of a stem-like Tc17 phenotype (IL-17α+, TCF1+). Tumor-bearing mice receiving T cells activated in the presence of PD-(L)1-axis disruption had better antitumor outcomes and a greater number of complete responses.
These data indicate that PD-1 blockade, when used with antitumor vaccines, acts primarily at the time of T cell activation, not exclusively within the tumor microenvironment. Consequently, PD-1 blockade may be best used when delivered concurrently with T cell activating agents such as vaccines.
© Author(s) (or their employer(s)) 2025. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ Group.

ABSTRACT Mesenchymal stem/stromal cell (MSC) therapy holds great promise as both a therapeutic option and as a biofactory, as cells produce therapeutic proteins to augment their efficacy in disease treatment. This study investigates the therapeutic effects and the mechanistic insights of alpha-1 antitrypsin overexpressing MSCs (AAT-MSCs) in diabetes prevention and treatment. A single infusion of AAT-MSCs not only delayed diabetes onset but reversed new-onset type 1 diabetes (T1D) in the nonobese diabetic (NOD) mice. Using single-cell RNA sequencing, flow cytometry, and functional analyses, we characterized the impact of AAT-MSCs on immune cells, particularly CD4 + and CD8 + T cells, in pancreatic lymph nodes (PLNs) and islets of NOD mice. AAT-MSCs enhanced the immunosuppressive function and the communication of regulatory T cells (Tregs) with other immune cells while reducing the numbers of T helper 1 (Th1) cells and CD8 + cytotoxic T cells. In vitro experiments further confirmed the capacity of AAT-MSCs to promote the proliferation of Tregs, which consequently fostered an exhausted phenotype in CD8 + T cells, thereby facilitating β cell survival and potentially aiding in diabetes remission. Thus, our findings underscore the significant protective effects of AAT-MSCs, delineate their novel mechanistic insight on recipient immune cells, and provide evidence for the clinical application of AAT-MSCs in treating T1D.

Nonobese diabetic (NOD) mice are a widely used animal model to study mechanisms leading to autoimmune diabetes. A gluten-free diet reduces and delays the incidence of diabetes in NOD mice, but the underlying mechanisms remain largely unknown. In this study, we performed single-cell transcriptomic and flow cytometry analysis of T cells and innate lymphocytes in the spleen and pancreatic lymph nodes of NOD mice fed a gluten-free or standard diet. We observed that the gluten-free diet did not induce a substantial alteration in the abundance or phenotype of any lymphocyte subset that would directly explain its protective effect against diabetes. However, the gluten-free diet induced subtle changes in the differentiation of subsets with previously proposed protective roles in diabetes development, such as Tregs, activated γδT cells, and NKT cells. Globally, the gluten-free diet paradoxically promoted activation and effector differentiation across multiple subpopulations and induced genes regulated by IL-2, IL-7, and IL-15. In contrast, the standard diet induced type I interferon-responsive genes. Overall, the gluten-free diet might prevent diabetes in NOD mice by inducing small-scale changes in multiple cell types rather than acting on a specific lymphocyte subset.
© 2025 The Author(s). European Journal of Immunology published by Wiley‐VCH GmbH.