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Key Points The hallmark fever response during infection and disease has been maintained throughout hundreds of millions of years in endothermic (warm-blooded) and ectothermic (cold-blooded) species. Febrile temperatures boost the probability of an effective immune response by stimulating both the innate and the adaptive arms of the immune system. The pyrogenic cytokine interleukin-6 (IL-6) contributes to two phases of the febrile response: it elevates the core body temperature via thermoregulatory autonomic mechanisms, and it also serves as a thermally sensitive effector molecule that amplifies lymphocyte trafficking into lymphoid organs. There is emerging evidence that adrenergic signalling pathways associated with thermogenesis can greatly influence immune cell function. Thus, the thermal element of fever serves as a systemic alert system that broadly promotes immune surveillance in the setting of infection and disease. This Review considers the impact of host temperature on the immune system. In particular, the authors focus on how the thermal element of the fever response can shape both innate and adaptive immune responses. Fever is a cardinal response to infection that has been conserved in warm-blooded and cold-blooded vertebrates for more than 600 million years of evolution. The fever response is executed by integrated physiological and neuronal circuitry and confers a survival benefit during infection. In this Review, we discuss our current understanding of how the inflammatory cues delivered by the thermal element of fever stimulate innate and adaptive immune responses. We further highlight the unexpected multiplicity of roles of the pyrogenic cytokine interleukin-6 (IL-6), both during fever induction and during the mobilization of lymphocytes to the lymphoid organs that are the staging ground for immune defence. We also discuss the emerging evidence suggesting that the adrenergic signalling pathways associated with thermogenesis shape immune cell function.

An immune response must be tightly controlled so that it will be commensurate with the level of response needed to protect the organism without damaging normal tissue. The roles of cytokines and chemokines in orchestrating these processes are well known, but although stress has long been thought to also affect immune responses, the underlying mechanisms were not as well understood. Recently, the role of nerves and, specifically, the sympathetic nervous system, in regulating immune responses is being revealed. Generally, an acute stress response is beneficial but chronic stress is detrimental because it suppresses the activities of effector immune cells while increasing the activities of immunosuppressive cells. In this review, we first discuss the underlying biology of adrenergic signaling in cells of both the innate and adaptive immune system. We then focus on the effects of chronic adrenergic stress in promoting tumor growth, giving examples of effects on tumor cells and immune cells, explaining the methods commonly used to induce stress in preclinical mouse models. We highlight how this relates to our observations that mandated housing conditions impose baseline chronic stress on mouse models, which is sufficient to cause chronic immunosuppression. This problem is not commonly recognized, but it has been shown to impact conclusions of several studies of mouse physiology and mouse models of disease. Moreover, the fact that preclinical mouse models are chronically immunosuppressed has critical ramifications for analysis of any experiments with an immune component. Our group has found that reducing adrenergic stress by housing mice at thermoneutrality or treating mice housed at cooler temperatures with β-blockers reverses immunosuppression and significantly improves responses to checkpoint inhibitor immunotherapy. These observations are clinically relevant because there are numerous retrospective epidemiological studies concluding that cancer patients who were taking β-blockers have better outcomes. Clinical trials testing whether β-blockers can be repurposed to improve the efficacy of traditional and immunotherapies in patients are on the horizon.

The abscopal effect following ionizing radiation therapy (RT) is considered to be a rare event. This effect does occur more frequently when combined with other therapies, including immunotherapy. Here we demonstrate that the frequency of abscopal events following RT alone is highly dependent upon the degree of adrenergic stress in the tumor-bearing host. Using a combination of physiologic, pharmacologic and genetic strategies, we observe improvements in the control of both irradiated and non-irradiated distant tumors, including metastatic tumors, when adrenergic stress or signaling through β-adrenergic receptor is reduced. Further, we observe cellular and molecular evidence of improved, antigen-specific, anti-tumor immune responses which also depend upon T cell egress from draining lymph nodes. These data suggest that blockade of β2 adrenergic stress signaling could be a useful, safe, and feasible strategy to improve efficacy in cancer patients undergoing radiation therapy. Abscopal responses in patients and preclinical models following radiation therapy are rare. Here the authors show that, in murine tumor models, reducing adrenergic stress or β2-adrenergic receptor signalling not only improves control of the irradiated tumor but significantly increases abscopal events.

We show here that fundamental aspects of antitumor immunity in mice are significantly influenced by ambient housing temperature. Standard housing temperature for laboratory mice in research facilities is mandated to be between 20–26 °C; however, these subthermoneutral temperatures cause mild chronic cold stress, activating thermogenesis to maintain normal body temperature. When stress is alleviated by housing at thermoneutral ambient temperature (30–31 °C), we observe a striking reduction in tumor formation, growth rate and metastasis. This improved control of tumor growth is dependent upon the adaptive immune system. We observe significantly increased numbers of antigen-specific CD8 ⁺ T lymphocytes and CD8 ⁺ T cells with an activated phenotype in the tumor microenvironment at thermoneutrality. At the same time there is a significant reduction in numbers of immunosuppressive MDSCs and regulatory T lymphocytes. Notably, in temperature preference studies, tumor-bearing mice select a higher ambient temperature than non-tumor-bearing mice, suggesting that tumor-bearing mice experience a greater degree of cold-stress. Overall, our data raise the hypothesis that suppression of antitumor immunity is an outcome of cold stress-induced thermogenesis. Therefore, the common approach of studying immunity against tumors in mice housed only at standard room temperature may be limiting our understanding of the full potential of the antitumor immune response.

Myeloid derived suppressor cells (MDSCs) are key regulators of immune responses and correlate with poor outcomes in hematologic malignancies. Here, we identify that MDSC mitochondrial fitness controls the efficacy of doxorubicin chemotherapy in a preclinical lymphoma model. Mechanistically, we show that triggering STAT3 signaling via β2-adrenergic receptor (β2-AR) activation leads to improved MDSC function through metabolic reprograming, marked by sustained mitochondrial respiration and higher ATP generation which reduces AMPK signaling, altering energy metabolism. Furthermore, induced STAT3 signaling in MDSCs enhances glutamine consumption via the TCA cycle. Metabolized glutamine generates itaconate which downregulates mitochondrial reactive oxygen species via regulation of Nrf2 and the oxidative stress response, enhancing MDSC survival. Using β2-AR blockade, we target the STAT3 pathway and ATP and itaconate metabolism, disrupting ATP generation by the electron transport chain and decreasing itaconate generation causing diminished MDSC mitochondrial fitness. This disruption increases the response to doxorubicin and could be tested clinically. Myeloid derived suppressor cells (MDSC) are associated with tumourigenesis and therapy response. Here, the authors show that beta 2-adrenergic receptor activation in MDSC leads to metabolic rewiring which regulates chemotherapy response in preclinical models of blood cancer.

Long conserved mechanisms maintain homeostasis in living creatures in response to a variety of stresses. However, continuous exposure to stress can result in unabated production of stress hormones, especially catecholamines, which can have detrimental health effects. While the long-term effects of chronic stress have well-known physiological consequences, recent discoveries have revealed that stress may affect therapeutic efficacy in cancer. Growing epidemiological evidence reveals strong correlations between progression-free and long-term survival and β-blocker usage in cancer patients. In this review, we summarize the current understanding of how the catecholamines, epinephrine and norepinephrine, affect cancer cell survival and tumor progression. We also highlight new data exploring the potential contributions of stress to immunosuppression in the tumor microenvironment and the implications of these findings for the efficacy of immunotherapies.

Breast cancer (BC) patients experience increased stress with elevated cortisol levels, increasing risk of cancer recurrence. Cortisol binds to a cytoplasmic receptor, glucocorticoid receptor (GR) encoded by GR gene (NR3C1). We hypothesized that not only cancer cells, but even immune cells in the tumor microenvironment (TME) may contribute to GR expression in bulk tumor and influence prognosis. To test this, mRNA expression data was accessed from METABRIC and TCGA. “High” and “low” expression was based on highest and lowest quartiles of NR3C1 gene expression, respectively. Single-cell sequencing data were obtained from GSE75688 and GSE114725 cohorts. Computer algorithms CIBERSORT, Gene Set Enrichment Analysis and TIMER were used. GR-high BC has better median disease-free and disease-specific survival. Single cell sequencing data showed higher GR expression on immune cells compared to cancer and stromal cells. Positive correlation between GR-high BC and CD8+ T-cells was noted. In GR-high tumors, higher cytolytic activity (CYT) with decreased T-regulatory and T-follicular helper cells was observed. High GR expression was associated with lower proliferation index Ki67, enriched in IL-2_STAT5, apoptosis, KRAS, TGF-β signaling, and epithelial-to-mesenchymal transition. Immune cells significantly contribute to GR expression of bulk BC. GR-high BC has a favorable TME with higher CYT with favorable outcomes.

The mechanisms underlying the metabolic adaptation of myeloid cells within the tumor microenvironment remain incompletely understood. Here, we identify 6-phosphogluconate dehydrogenase (6PGD), a rate-limiting enzyme in the pentose phosphate pathway (PPP), as an important regulator of monocytic-myeloid derived suppressor cell (M-MDSC) function. Our findings reveal that tumor M-MDSCs upregulate 6PGD expression via IL-6/STAT3 signaling. Blocking 6PGD, using either genetic or pharmacological approaches, impairs the immunosuppressive function of M-MDSCs and suppresses tumor growth. Mechanistically, 6PGD inhibition leads to the accumulation of its substrate, 6-phosphogluconate (6PG), within M-MDSCs, activates the JNK1-IRS1 and PI3K-AKT-pDRP1 signaling pathways, leading to mitochondrial fragmentation and elevated mitochondrial reactive oxygen species (ROS). This metabolic shift drives M-MDSCs toward an M1-like proinflammatory phenotype. Furthermore, 6PGD blockade synergizes with anti-PD-1 immunotherapy in a preclinical tumor model, substantially improving therapeutic outcomes. Our data reveals 6PGD as a possible therapeutic target to disrupt M-MDSC function and improve cancer immunotherapy outcomes. Myeloid derived suppressor cells (MDSC) use different metabolic mechanisms to adapt to the tumour microenvironment. Here the authors show that 6-phosphogluconate dehydrogenase (6PGD) is important for MSDC function and that blockade of 6PGD impaired MDSC function and suppresses tumour growth leading to metabolic and functional changes in the MDSC and a more pro-inflammatory phenotype.

Vascularized composite tissue allotransplantation (VCA) has transformed patients’ lives by enabling limb, face, abdominal wall, and penile transplants. Despite advancements in screening and immunosuppression, chronic rejection continues to limit the success of VCA. Lack of reliable preclinical models exacerbates this challenge. Here, we report on new mouse models of chronic rejection following heterotopic hind limb VCA. We employed different levels of MHC mismatch using CD8 knockout C57BL/6 mice as recipients along with BALB/c or B6 H2-Ab1 bm12 mice as donors. Transient CD4 T cell depletion was induced to allow graft maturation. Evaluation included gross findings, changes in immune status changes, production of donor-specific antibodies (DSA), C4d levels, and histopathological alterations. Two chronic rejection models displayed common features of clinical chronic graft rejection, such as skin stricture, hair loss, adnexal atrophy, extensive fibrosis and mast cell infiltration without widespread necrotic changes common in acute rejection. Similar to chronic rejection patients, large populations of activated B and plasma cells were detected in the recipient’s immune system as well as increased DSA and C4d production. Collectively, our models closely replicate the immunological and histopathological aspects of chronic graft rejection post-VCA, and could provide a new platform for evaluation of novel therapeutic interventions prior to clinical evaluation.

Background Esophageal cancer (ESC) is an aggressive disease which often presents at an advanced stage. Despite trimodal therapy, 40–50% patients can develop metastatic disease by 18 months. Identification of patients at risk for metastatic spread is challenging with need for improved prognostication. We investigated whether the immune landscape of pretreatment tissue was associated with relapse in ESC patients. Methods Between April 2010 and October 2018, we identified 25 patients who had undergone trimodal therapy for ESC and had pretreatment biopsies suitable for analyses. We performed high-throughput multispectral immunofluorescence (mIF) analysis on formalin-fixed paraffin embedded biopsy samples. Analysis of 27 unique populations via immune and exhaustion mIF panels was performed and expression was normalized to total cell counts. Results Of the 25 patients analyzed, the median follow-up time was 23.9 months, during which 12 (48%) patients suffered a relapse with a median time to progression of 13.1 months. mIF revealed higher expression of HLA-DR ( p  = 0.019), CD8/LAG3 ( p  = 0.046), and CD8/CTLA4 ( p  = 0.027) among patients without relapse. Time to progression (TTP) and disease-specific survival (DSS) were stratified by median expression of each significant subpopulation and formally tested by the log-rank test. Higher than median expression of HLA-DR ( p  = 0.027), CD8/LAG3 ( p  = 0.039), and CD8/CTLA4 ( p  = 0.039) were significantly associated with TTP. Similarly, HLA-DR ( p  = 0.0069) and CD8/CTLA4 ( p  = 0.036) were significantly associated with improved DSS, whereas no significant observations were found with CD8/LAG3 ( p  = 0.11) expression. Stromal, but not tumoral expression of CD163 and CD163/PDL1 were significantly associated with improved TTP and DSS. Conclusions High expression of HLA-DR, CD8/CTLA4, and stromal expression of CD163 and CD163/PDL1 within pretreatment biopsy ESC samples was associated with significantly reduced rates of relapse. Increased presence of these markers suggests that an improved immune landscape is associated with less aggressive disease and may provide an opportunity for risk-based treatment strategies.