Activating the immune co-stimulatory receptor 4-1BB (CD137) with agonist antibody binding and crosslinking-inducing agents that elicit 4-1BB intracellular signaling potentiates the antitumor responses of CD8 T cells. However, the underlying in-depth mechanisms remain to be defined. Here, we show that agonistic 4-1BB treatment of activated CD8+ T cells under continuous antigenic stimulation are more metabolically vulnerable to redox perturbation by ablation of intracellular glutathione (GSH) and glutathione peroxidase 4 (GPX4) inhibition. Further, genetic deletion of adenosine A2B receptor (A2BR) induces superior survival and expansion advantage of competent CD8+ T cells with agonistic 4-1BB costimulation, leading to more effective antitumor efficacy of adoptive cell therapy (ACT). Mechanistically, A2BR deletion helps sustain the increased energy and biosynthetic requirements through the GSH-GPX4 axis upon 4-1BB costimulation. A2BR deletion in combination with agonistic 4-1BB costimulation displays a greater ability to promote antitumor CD8+ effector T cell survival and expansion while mitigating T cell exhaustion. Thus, the A2BR pathway plays an important role in metabolic reprogramming with potentiation of the GSH-GPX4 cascade upon agonistic 4-1BB costimulation that allows the fine-tuning of the antitumor responses of CD8+ T cells.

Gram-negative bacillary bacteremia poses a significant threat, ranking among the most severe infectious diseases capable of triggering life-threatening sepsis. Despite the unambiguous involvement of neutrophils in this potentially fatal disease, there are limited data about the molecular signaling mechanisms, phenotype, and function of human neutrophils during the early phase of gram-negative bacillary bacteremia.
By using an unbiased proteomics and flow cytometry approach, we identified an antigen-presenting cell (APC)-like phenotype in human peripheral blood neutrophils (PMN) with MHC class II molecule expression in the early phase of bacteremia. Using an in-vitro model of GM-CSF-mediated induction of APC-like phenotype in PMN, we investigated downstream signaling pathways leading to MHC class II expression.
GM-CSF stimulation of neutrophils leads to the activation of three major signaling pathways, the JAK-STAT, the mitogen-activated protein kinase (MAPK), and the phosphoinositide 3-kinase (PI3K)-Akt-mTOR pathways, while MHC class II induction is mediated by a MAPK-p38-MSK1-CREB1 signaling cascade and the MHC class II transactivator CIITA in a strictly JAK1/2 kinase-dependent manner.
This study provides new insights into the signaling pathways that induce MHC class II expression in neutrophils, highlighting the potential for therapeutic targeting of JAK1/2 signaling in the treatment of gram-negative bacteremia and sepsis. Understanding these mechanisms may open up novel approaches for managing inflammatory responses during sepsis.
Copyright © 2024 Forrer, Palianina, Stühler, Kreuzaler, Roux, Li, Schmutz, Burckhardt, Franzeck, Finke, Schmidt, Bumann and Khanna.

Acute myeloid leukemia (AML) is a heterogeneous malignant condition characterized by massive infiltration of poorly differentiated white blood cells in the blood stream, bone marrow, and extramedullary sites. During leukemic development, hepatosplenomegaly is expected to occur because large blood volumes are continuously filtered through these organs. We asked whether infiltration of leukemic blasts initiated a response that could be detected in the interstitial fluid phase of the spleen and liver.
We used a rat model known to mimic human AML in growth characteristics and behavior. By cannulating efferent lymphatic vessels from the spleen and liver, we were able to monitor the response of the microenvironment during AML development.
Flow cytometric analysis of lymphocytes showed increased STAT3 and CREB signaling in spleen and depressed signaling in liver, and proteins related to these pathways were identified with a different profile in lymph and plasma in AML compared with control. Additionally, several proteins were differently regulated in the microenvironment of spleen and liver in AML when compared with control.
Interstitial fluid, and its surrogate efferent lymph, can be used to provide unique information about responses in AML-infiltered organs and substances released to the general circulation during leukemia development.
© 2023 John Wiley & Sons Ltd.

Prostaglandin E2 (PGE2) promotes an immunosuppressive microenvironment in cancer, partly by signaling through four receptors (EP1, EP2, EP3, and EP4) on T cells. Here, we comprehensively characterized PGE2 signaling networks in helper, cytotoxic, and regulatory T cells using a phosphoproteomics and phosphoflow cytometry approach. We identified ~1500 PGE2-regulated phosphosites and several important EP1–4 signaling nodes, including PKC, CK2, PKA, PI3K, and Src. T cell subtypes exhibited distinct signaling pathways, with the strongest signaling in EP2-stimulated CD8+ cells. EP2 and EP4, both of which signal through Gαs, induced similar signaling outputs, but with distinct kinetics and intensity. Functional predictions from the observed phosphosite changes revealed PGE2 regulation of key cellular and immunological processes. Last, network modeling suggested signal integration between the receptors and a substantial contribution from G protein–independent signaling. This study offers a comprehensive view of the different PGE2-regulated phosphoproteomes in T cell subsets, providing a valuable resource for further research on this physiologically and pathophysiologically important signaling system.

Eicosanoids and intracellular signaling pathways are potential targets for host-directed therapy (HDT) in tuberculosis (TB). We have explored the effect of cyclooxygenase 2 inhibitor (COX-2i) treatment on eicosanoid levels and signaling pathways in monocytes.
Peripheral blood mononuclear cells isolated from TB patients included in a randomized phase I clinical trial of standard TB treatment with (n=21) or without (n=18) adjunctive COX-2i (etoricoxib) were analyzed at baseline, day 14 and day 56. Plasma eicosanoids were analyzed by ELISA and liquid chromatography-mass spectrometry (LC-MS), plasma cytokines by multiplex, and monocyte signaling by phospho-flow with a defined set of phospho-specific antibodies.
Lipoxygenase (LOX)-derived products (LXA4 and 12-HETE) and pro-inflammatory cytokines were associated with TB disease severity and were reduced during TB therapy, possibly accelerated by adjunctive COX-2i. Phosphorylation of p38 MAPK, NFkB, Erk1/2, and Akt in monocytes as well as plasma levels of MIG/CXCL9 and procalcitonin were reduced in the COX-2i group compared to controls.
COX-2i may reduce excess inflammation in TB via the LOX-pathway in addition to modulation of phosphorylation patterns in monocytes. Immunomodulatory effects of adjunctive COX-2i in TB should be further investigated before recommended for use as a HDT strategy.
Copyright © 2021 Jøntvedt Jørgensen, Nore, Aass, Layre, Nigou, Mortensen, Tasken, Kvale, Jenum, Tonby and Dyrhol-Riise.