Expansion of tumor-associated Treg cells upon disruption of a CTLA-4-dependent feedback loop Graphical abstract Highlights d The TCR repertoire of Treg cells is enriched for reactivity to antigens in the TME d Tumor Treg cells use CTLA-4 to destabilize their own interactions with dendritic cells d CTLA-4 blockade causes the CD28-mediated expansion of tumor-associated Treg cells d Following CTLA-4 blockade, Treg cells continue to promote tumor immune tolerance

Materials are needed to increase the stability and half-life of therapeutic proteins during delivery. These materials should be biocompatible and biodegradable. Here, we demonstrate that enzymes and immunoproteins can be...

PD-1 blockade unleashes the potent antitumor activity of CD8 cells but can also promote immunosuppressive T regulatory (Treg) cells, which may worsen response to immunotherapy. Tumor Treg inhibition is a promising strategy to overcome therapeutic resistance; however, the mechanisms supporting tumor Tregs during PD-1 immunotherapy are largely unexplored. Here, we report that PD-1 blockade increases tumor Tregs in mouse models of immunogenic tumors, including melanoma, and metastatic melanoma patients. Unexpectedly, Treg accumulation was not caused by Treg-intrinsic inhibition of PD-1 signaling but instead depended on an indirect effect of activated CD8 cells. CD8 cells colocalized with Tregs within tumors and produced IL-2, especially after PD-1 immunotherapy. IL-2 upregulated the anti-apoptotic protein ICOS on tumor Tregs, causing their accumulation. ICOS signaling inhibition before PD-1 immunotherapy resulted in increased control of immunogenic melanoma. Thus, interrupting the intratumor CD8:Treg crosstalk is a novel strategy that may enhance the efficacy of immunotherapy in patients.

Regulatory T (Treg) cells are indispensable for the maintenance of immune tolerance and the prevention of autoimmunity; however, how Treg cells retain their homeostasis with immune suppressive function remains largely unclear. Here we report that deubiquitinase CYLD plays a critical role in the maintenance of Treg cells. Foxp3− specific CYLD knockout mice showed severe pulmonary inflammation due to preferential migration of Treg cells into the lung and increased interleukin-4 (IL-4) production compared to control mice, which was reversed by the deletion of IL-4. Genome-wide microarray analysis unveiled that Scinderin, a member of the actin-binding gelsolin family, was highly upregulated in CYLD-deficient Treg cells, which contributed to IL-4 production through complex formation with MEK/ERK. Increased IL-4 production by CYLD-deficient Treg cells was significantly rectified by Scinderin ablation. Our findings indicate that CYLD is essential to maintain Treg cell function through regulating Scinderin expression.