PD-1 Deficiency Research Articles

Obesity induces PD-1 on macrophages to suppress anti-tumour immunity.

Obesity is a leading risk factor for progression and metastasis of many cancers1,2, yet can in some cases enhance survival3-5 and responses to immune checkpoint blockade therapies, including anti-PD-1, which targets PD-1 (encoded by PDCD1), an inhibitory receptor expressed on immune cells6-8. Although obesity promotes chronic inflammation, the role of the immune system in the obesity-cancer connection and immunotherapy remains unclear. It has been shown that in addition to T cells, macrophages can express PD-19-12. Here we found that obesity selectively induced PD-1 expression on tumour-associated macrophages (TAMs). Type I inflammatory cytokines and molecules linked to obesity, including interferon-γ, tumour necrosis factor, leptin, insulin and palmitate, induced macrophage PD-1 expression in an mTORC1- and glycolysis-dependent manner. PD-1 then provided negative feedback to TAMs that suppressed glycolysis, phagocytosis and T cell stimulatory potential. Conversely, PD-1 blockade increased the level of macrophage glycolysis, which was essential for PD-1 inhibition to augment TAM expression of CD86 and major histocompatibility complex I and II molecules and ability to activate T cells. Myeloid-specific PD-1 deficiency slowed tumour growth, enhanced TAM glycolysis and antigen-presentation capability, and led to increased CD8+ T cell activity with a reduced level of markers of exhaustion. These findings show that obesity-associated metabolic signalling and inflammatory cues cause TAMs to induce PD-1 expression, which then drives a TAM-specific feedback mechanism that impairs tumour immune surveillance. This may contribute to increased cancer risk yet improved response to PD-1 immunotherapy in obesity.

Human inherited PD-L1 deficiency is clinically and immunologically less severe than PD-1 deficiency.

We previously reported two siblings with inherited PD-1 deficiency who died from autoimmune pneumonitis at 3 and 11 years of age after developing other autoimmune manifestations, including type 1 diabetes (T1D). We report here two siblings, aged 10 and 11 years, with neonatal-onset T1D (diagnosed at the ages of 1 day and 7 wk), who are homozygous for a splice-site variant of CD274 (encoding PD-L1). This variant results in the exclusive expression of an alternative, loss-of-function PD-L1 protein isoform in overexpression experiments and in the patients' primary leukocytes. Surprisingly, cytometric immunophenotyping and single-cell RNA sequencing analysis on blood leukocytes showed largely normal development and transcriptional profiles across lymphoid and myeloid subsets in the PD-L1-deficient siblings, contrasting with the extensive dysregulation of both lymphoid and myeloid leukocyte compartments in PD-1 deficiency. Our findings suggest that PD-1 and PD-L1 are essential for preventing early-onset T1D but that, unlike PD-1 deficiency, PD-L1 deficiency does not lead to fatal autoimmunity with extensive leukocytic dysregulation.

Mechanisms of pTreg development from anergic precursors

Abstract Regulatory T cells (Tregs) are generated either in the thymus or periphery. While factors governing ‘natural’ thymus-derived Treg (nTreg) development are well described, there is limited understanding of those directing peripheral regulatory T cell (pTreg) differentiation. Using a mouse model of oral tolerance, we demonstrate that T cells must first enter a state of anergy prior to becoming pTreg, suggesting a two-stage process. Stage 1 is characterized by T cell anergy with prominent induction of ‘checkpoint’ inhibitory receptors, most notably PD-1 and CD200. Stage 2 then follows with pTreg conversion or, alternatively, adoption of a ‘deep’ anergic state. Given this induction of inhibitory receptors, we assessed the impact of PD-1 deficiency and found that T cells proliferate more and convert less to pTreg. Intriguingly, we also find that PD-1 expression distinguishes pTreg derived from anergic precursors from those derived from non-anergic precursors. Based on scRNAseq data showing that IL-2-STAT5 signaling is highly active in pTreg, we also assessed the role of IL-2Ra and STAT5 and found that both are strictly required for induction of pTreg, suggesting that this pathway drives transition from Stage 1 to Stage 2 tolerance. Taken together, our data shows that transition from Treg-independent (Stage 1) to Treg-dependent (Stage 2) tolerance is driven by cell extrinsic signals provided by inhibitory receptors and IL-2-STAT5 signaling which combine to induce pTreg development.

Abstract 1369: PD-1 directly suppresses macrophage metabolism to restrict anti-tumor immunity in an obesity-cancer connection

Abstract Obesity has been established as a leading risk factor for many cancers and can drive tumor progression and metastasis. Paradoxically, obesity has in some cases been associated with better survival and improved response to immune checkpoint blockade therapies. The role of the immune system in the obesity-cancer connection and how obesity affects immunotherapy responses, however, have been unclear. Here we show that obesity enhanced PD-1 expression on macrophages to reduce phagocytosis and antigen presentation to T cells that correlated with reduced T cell expansion and function. This obesity associated immune dysfunction, however, primed for enhanced anti-tumor response to PD-1 blockade. Single cell RNAseq showed obesity remodels myeloid and T cell populations but does not impact non-immune cell populations such as fibroblasts and epithelial cells. Specifically, obesity increased the overall number of tumor-associated macrophages (TAM) while effector T cells were decreased in abundance. Interestingly, the frequency of macrophages expressing PD-1 increased, while the remaining T cells maintained similar or reduced PD-1 expression and appeared less activated. Further, T cell depletion from the tumor microenvironment, enhanced macrophage PD-1 expression and worsened PD1-associated TAM dysfunction in an obesity enhanced manor. Obesity associated cytokines and adipokines including IFN-ã, leptin and insulin induced PD-1 expression on macrophages. This expression is associated with mTOR and c-myc activation signaling pathways; as such inhibiting these signaling pathways blocked PD1 expression. Bulk RNA sequencing analysis revealed PD-1+ TAMs had an altered gene profile compared to PD-1− TAMs. PD1 expressing macrophages exhibited increased mitochondrial respiration and expression of oxidative phosphorylation, increased lipid uptake and increased cell cycling related genes. Conversely PD1- TAMs exhibited increased phagocytosis and antigen presentation. PD-1/PDL1 interaction directly regulated TAMs, as recombinant PDL-1 reduced glycolysis and phagocytosis in purified macrophages, and these effects could be reversed with blocking PD-1 antibody. Conversely, PD-1−/− TAMs had reduced lipid uptake but high rates of glycolysis, phagocytosis, and expression of MHC-II. Myeloid-specific PD-1 deficiency correlated with slower tumor growth and decreased LAG3 and increased CD69 on CD8 T cells. In addition, myeloid specific PD1 deficiency enhanced TAM antigen presentation through OVA specific CD8 T cell activation. These findings identify PD-1 as a metabolic regulator in TAM dysfunction and reveal a unique PD-1 mediated and macrophage-specific mechanism for immune tumor surveillance and checkpoint blockade. This may contribute to improved immunotherapy response in TAM-enriched tumors and obesity. Citation Format: Jackie Bader, Jeffrey Rathmell. PD-1 directly suppresses macrophage metabolism to restrict anti-tumor immunity in an obesity-cancer connection [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 1369.

Nr4a1 marks a distinctive ILC2 activation subset in the mouse inflammatory lung

BackgroundGroup 2 innate lymphoid cells (ILC2s) are critical sources of type 2 cytokines and represent one of the major tissue-resident lymphoid cells in the mouse lung. However, the molecular mechanisms underlying ILC2 activation under challenges are not fully understood.ResultsHere, using single-cell transcriptomics, genetic reporters, and gene knockouts, we identify four ILC2 subsets, including two non-activation subsets and two activation subsets, in the mouse acute inflammatory lung. Of note, a distinct activation subset, marked by the transcription factor Nr4a1, paradoxically expresses both tissue-resident memory T cell (Trm), and effector/central memory T cell (Tem/Tcm) signature genes, as well as higher scores of proliferation, activation, and wound healing, all driven by its particular regulons. Furthermore, we demonstrate that the Nr4a1+ILC2s are restrained from activating by the programmed cell death protein-1 (PD-1), which negatively modulates their activation-related regulons. PD-1 deficiency places the non-activation ILC2s in a state that is prone to activation, resulting in Nr4a1+ILC2 differentiation through different activation trajectories. Loss of PD-1 also leads to the expansion of Nr4a1+ILC2s by the increase of their proliferation ability.ConclusionsThe findings show that activated ILC2s are a heterogenous population encompassing distinct subsets that have different propensities, and therefore provide an opportunity to explore PD-1's role in modulating the activity of ILC2s for disease prevention and therapy.

Brain-specific Pd1 deficiency leads to cortical neurogenesis defects and depressive-like behaviors in mice.

Embryonic neurogenesis is tightly regulated by multiple factors to ensure the precise development of the cortex. Deficiency in neurogenesis may result in behavioral abnormalities. Pd1 is a well-known inhibitory immune molecule, but its function in brain development remains unknown. Here, we find brain specific deletion of Pd1 results in abnormal cortical neurogenesis, including enhanced proliferation of neural progenitors and reduced neuronal differentiation. In addition, neurons in Pd1 knockout mice exhibit abnormal morphology, both the total length and the number of primary dendrites were reduced. Moreover, Pd1cKO mice exhibit depressive-like behaviors, including immobility, despair, and anhedonia. Mechanistically, Pd1 regulates embryonic neurogenesis by targeting Pax3 through the β-catenin signaling pathway. The constitutive expression of Pax3 partly rescues the deficiency of neurogenesis in the Pd1 deleted embryonic brain. Besides, the administration of β-catenin inhibitor, XAV939, not only rescues abnormal brain development but also ameliorates depressive-like behaviors in Pd1cKO mice. Simultaneously, Pd1 plays a similar role in human neural progenitor cells (hNPCs) proliferation and differentiation. Taken together, our findings reveal the critical role and regulatory mechanism of Pd1 in embryonic neurogenesis and behavioral modulation, which could contribute to understanding immune molecules in brain development.

PD-1 Deficiency in Regulatory T Cells May be Involved in the Pathogenesis of Takayasu's Arteritis.

This study aims to investigate whether PD-1 expressions are abnormal in patients with TAK. PD-1 expression was analyzed by flow cytometry. Serum cytokines IL-10, IL-7, IL-2, IL-15, CCL2, CCL3, and CXCL10 were detected using a cytokine cytometric bead array. Immunohistochemistry staining analysis was used to test PD-1 and programmed death-ligand 1 (PD-L1) expression in the aorta of three patients with TAK and three patients with atherosclerosis as controls. The mean fluorescence intensity of PD-1 in CD4+PD-1+ cells was decreased in patients with TAK and the frequency of CD4+Foxp3-PD-1+ cells among CD4+T cells was also decreased in peripheral blood relative to healthy controls (P < .05). The percentage of CD4+CD25+Foxp3+PD-1+ cells in the CD4+CD25+T cell population was lower in patients with TAK than in healthy control and was lower in active TAK group (P < .05). Comparing PD-1 and PDL-1 expression in aorta tissue showed that patients with TAK tended to have lower levels than patients with atherosclerosis, but the difference was not significant (P > .05). Patients with TAK had higher serum levels of IL-10, IL-7, CCL2, and CCL3 (P < .05). Abnormal expression of PD-1 in serum and aorta tissue of patients with TAK may contribute to TAK pathogenesis. PD-1 expression in both peripheral blood and aorta tissue of TAK patients decreased relative to healthy controls, indicating that PD-1 might be involved in TAK pathogenesis.

Programmed cell death protein 1 (PD1) deficiency induces cardiac inflammation during baseline conditions and ischemia/reperfusion injury

Abstract Background The Programmed cell death protein 1 (PD1) immune checkpoint is densely expressed on cardiac endothelial cells. The increasing clinical application of immune checkpoint inhibitor therapy targeting PD1 for the treatment of advanced malignancies has revealed profound cardiovascular side effects that have recently paralleled in a preclinical model. However, the effects of PD1 deficiency during baseline conditions and myocardial injury are so far unknown. Purpose This study aims to assess the impact of PD1 deficiency on myocardia immunity, and to evaluate the relevance of PD1 signalling in cardiac disease. Methods C57BL/6J wild-type mice and C57BL/6J Pdcd1−/− mice were purchased and bred at the animal facility. In-vivo ischaemia/reperfusion (I/R) injury was applied to assess the response in cardiac injury. In brief, mice were anesthetised followed by lateral thoracotomy and ligation of the left coronary artery for 45 min. For flow cytometry, hearts were removed and subjected to an enzymatic digestion. Single cell solutions were stained with different antibody panels to assess cardiac immune cells and the expression of programmed cell death protein 1 ligand 1 (PDL1). Western blot was conducted after homogenization of snap-frozen heart tissue using specific primary and corresponding secondary antibodies. Immunofluorescence and conventional haematoxylin and eosin stain from 4 μm sections were used to visualize the distribution of PDL1 in cardiac tissue. Results While no overt cardiac phenotype was observed in Pdcd1−/− mice, a profound upregulation of pro-inflammatory cytokines was determined during baseline conditions, including interleukin (IL) 1α IL4, and extracellular-signal regulated kinase (ERK) 1/2. NADPH oxidase 1 (NOX1) which is involved in production of reactive oxygen species and endothelial injury response was downregulated in Pdcd1−/− mice. Following I/R injury, a significant decline in endothelial PDL1 expression was observed, which was attributed to changes in the area at risk, as shown by immunofluorescence staining. The infarct size following in-vivo I/R injury was not altered upon PD1-deficiency as determined by TTC staining. However, flow cytometry determined increased cell numbers of distinct leukocyte subsets during reperfusion-related inflammation. Conclusion Deficiency of PD1/PDL1 signalling shows distinct inflammatory changes in cardiac tissue at baseline and I/R injury. The results indicate that relevant PD1-related detrimental effects are not limited to complications from cancer therapy but can be expected in various forms of cardiovascular disease, hence requiring further investigations. Funding Acknowledgement Type of funding sources: Public hospital(s). Main funding source(s): Department of Cardiology and Vascular Medicine, West German Heart and Vascular Center, University Hospital Essen, Germany

Human PD-1 agonist treatment alleviates neutrophilic asthma by reprogramming T cells

Neutrophilic asthma is associated with disease severity and corticosteroid insensitivity. Novel therapies are required to manage this life-threatening asthma phenotype. Programmed cell death protein-1 (PD-1) is a key homeostatic modulator of the immune response for T-cell effector functions. We sought to investigate the role of PD-1 in the regulation of acute neutrophilic inflammation in a murine model of airway hyperreactivity (AHR). House dust mite was used to induce and compare neutrophilic AHR in wild-type and PD-1 knockout mice. Then, the therapeutic potential of a human PD-1 agonist was tested in a humanized mouse model in which the PD-1 extracellular domain is entirely humanized. Single-cell RNA sequencing and flow cytometry were mainly used to investigate molecular and cellular mechanisms. PD-1 was highly induced on pulmonary T cells in our inflammatory model. PD-1 deficiency was associated with an increased neutrophilic AHR and high recruitment of inflammatory cells to the lungs. Consistently, PD-1 agonist treatment dampened AHR, decreased neutrophil recruitment, and modulated cytokine production in a humanized PD-1 mouse model. Mechanistically, we demonstrated at the transcriptional and protein levels that the inhibitory effect of PD-1 agonist is associated with the reprogramming of pulmonary effector T cells that showed decreased number and activation. PD-1 agonist treatment is efficient in dampening neutrophilic AHR and lung inflammation in a preclinical humanized mouse model.

PD1 Deficiency Modifies Cardiac Immunity during Baseline Conditions and in Reperfused Acute Myocardial Infarction.

The programmed cell death protein 1 (PD1) immune checkpoint prevents inflammatory tissue damage by inhibiting immune reactions. Understanding the relevance of cardiac PD1 signaling may provide new insights into the inflammatory events under baseline conditions and disease. Here, we demonstrate distinct immunological changes upon PD1 deficiency in healthy hearts and during reperfused acute myocardial infarction (repAMI). In PD1-deficient mice, upregulated inflammatory cytokines were identified under baseline conditions including cardiac interleukins and extracellular signal-related kinase 1/2 (ERK1/2). A murine in vivo repAMI model to determine inflammatory changes in the early phase showed downregulation of the ligand PDL1, paralleled by an endothelial injury, indicated by loss of the CD31 signal. Immunofluorescence imaging showed decreased PDL1 expression specifically in the infarct zone, highlighting an involvement in PDL1 in myocardial injury response. Pharmacological depletion of PD1 prior to repAMI did not alter the area of infarction but led to increased numbers of CD8+ T cells in treated mice. We conclude that PD1/PDL1 signaling plays a significant role in healthy hearts and repAMI, emphasizing the relevance of adaptive immunity during myocardial injury. The findings highlight the risk for adverse outcomes from acute myocardial infarction in the growing group of patients receiving immune checkpoint inhibitor therapy.

PD-1 signaling facilitates activation of lymphoid tissue inducer cells by restraining fatty acid oxidation.

Anti-programmed death-1 (PD-1) immunotherapy that aims to restore T cell activity in cancer patients frequently leads to immune-related adverse events such as colitis. However, the underlying mechanism is still elusive. Here, we find that Pdcd1-deficient mice exhibit disrupted gut microbiota and aggravated dextran sulfate sodium (DSS)-induced colitis. In addition to T cells, PD-1 is also substantially expressed in colonic lymphoid tissue inducer (LTi) cells. During DSS-induced colitis, LTi cell activation is accompanied by increased PD-1 expression, whereas PD-1 deficiency results in reduced interleukin-22 (IL-22) production by LTi cells and exacerbated inflammation. Mechanistically, activated LTi cells reprogram their metabolism toward carbohydrate metabolism and fatty acid synthesis, while fatty acid oxidation (FAO) is unchanged. However, PD-1 deficiency leads to significantly elevated FAO in LTi cells, which in turn attenuates their activation and IL-22 production. Consistently, FAO suppression efficiently restores IL-22 production in Pdcd1-/- LTi cells. Thus, our study provides unforeseen mechanistic insight into colitis occurrence during anti-PD-1 immunotherapy through LTi cell metabolic reconfiguration.

The paradox of immune checkpoint inhibition re-activating tuberculosis.

By attenuating T-cell activation, immune checkpoints (ICs) limit optimal anti-tumour responses and IC inhibition (ICI) has emerged as a new therapy for a broad range of cancers. T-cell responses are indispensable to tuberculosis (TB) immunity in humans. However, boosting T-cell immunity in cancer patients by blocking the programmed cell death 1/programmed cell death ligand 1 (PD-1/PD-L1) axis can trigger re-activation of latent TB. This phenomenon appears to contradict the prevailing thought that enhancing T-cell immunity to Mycobacterium tuberculosis will improve immune control of this pathogen. In support of this anecdotal human data, several murine studies have shown that PD-1 deficiency leads to severe TB disease and rapid death. These observations warrant a serious reconsideration of what constitutes effective TB immunity and how ICs contribute to it. Through restraining T-cell responses, ICs are critical to preventing excessive tissue damage and maintaining a range of effector functions. Bolstering this notion, inhibitory receptors limit pathology in respiratory infections such as influenza, where loss of negative immune regulation resulted in progressive immunopathology. In this review, we analyse the mechanisms of ICs in general and their role in TB in particular. We conclude with a reflection on the emerging paradigm and avenues for future research.

The PD-1 Regulatory Axis Inhibits T Cell-Independent B Cell Memory Generation and Reactivation.

The inability of T cell-independent type 2 (TI-2) Ags to induce recall responses is a poorly understood facet of humoral immunity, yet critically important for improving vaccines. Using normal and VHB1-8 transgenic mice, we demonstrate that B cell-intrinsic PD-1 expression negatively regulates TI-2 memory B cell (Bmem) generation and reactivation in part through interacting with PDL1 and PDL2 on non-Ag-specific cells. We also identified a significant role for PDL2 expression on Bmems in inhibiting reactivation and Ab production, thereby revealing a novel self-regulatory mechanism exists for TI-2 Bmems This regulation impacts responses to clinically relevant vaccines, because PD-1 deficiency was associated with significantly increased Ab boosting to the pneumococcal vaccine after both vaccination and infection. Notably, we found a B cell-activating adjuvant enabled even greater boosting of protective pneumococcal polysaccharide-specific IgG responses when PD-1 inhibition was relieved. This work highlights unique self-regulation by TI-2 Bmems and reveals new opportunities for significantly improving TI-2 Ag-based vaccine responses.

Inherited human PD-1 deficiency underlies tuberculosis and autoimmunity

Abstract The pathogenesis of adverse reactions to PD-1 blockade immunotherapy, including tuberculosis (TB) and autoimmunity, remains poorly characterized. Here, we study a patient with inherited PD-1 deficiency who suffered from TB and died of pulmonary autoimmunity. The patient’s leukocytes displayed no PD-1 expression and did not respond to PD-1-mediated suppression. Similar to various inborn errors of immunity impairing interferon (IFN)-γ production and underlying TB, the patient’s lymphocytes poorly produced IFN-γ in response to mycobacterial stimuli owing to both the depletion of multiple IFN-γ-producing T and NK lymphocyte subsets, including Vδ2+ γδ T, MAIT, and CD56bright NK lymphocytes, and dysfunction of residual T lymphocytes. Another set of inborn errors, including STAT3 gain-of-function (GOF) mutations, trigger an expansion of CD4−CD8− double-negative (DN) αβ T cells and underlie lymphoproliferative autoimmunity. Remarkably, the patient displayed hepatosplenomegaly and expansion of total, activated, and RORγT+ DN αβ T cells, as observed in PD-1-deficient mice and cancer patients with PD-1 blockade. Mechanistically, the patient’s myeloid cells produced excessive amounts of STAT3-activating cytokines IL-6 and IL-23 upon stimulation with lipopolysaccharide. Overall, inherited human PD-1 deficiency underlies TB through undermining IFN-γ production by T and NK lymphocytes and lymphoproliferative autoimmunity through over-activating STAT3.

PD-1/PDL1 Blockade Exacerbates Pancreatic Damage and Immune Response in a Mouse Model of Acute Pancreatitis.

Programmed necrosis factor 1 (PD-1) is significantly overexpressed in lymphocytes, neutrophils, and macrophages and has been studied in depth in tumors. As a member of the negative costimulatory family of immune regulatory molecules, expression of PD-1 and its primary regulatory pathway are related to immune cells. Recently, PD-1 was demonstrated to be clinically important in inflammatory diseases, such as multiple sclerosis, glomerulonephritis, and inflammatory bowel disease. PD-1, a negative regulator molecule, was recently found to protect tissues from the inflammatory response and inflammatory cell infiltration. Conversely, PD-1 deficiency may contribute to the occurrence of a diverse array of inflammatory diseases. However, whether PD-1 regulates the pathogenesis of acute pancreatitis (AP) is unclear. AP is a noninfectious inflammatory disease with primary pathological manifestations that include edema, inflammatory cell infiltration, and acinar cell necrosis. Among these features, costimulatory molecules including PD-1/PDL1 play a critical role in the regulation of immune response and immune activation. Here, we first found that PD-1 is notably upregulated in neutrophils and macrophages in peripheral blood and pancreatic injury tissue in AP mice. PD-1 gene deficiency exacerbated pancreatic injury in an experimental mouse model of AP. We observed more severe pancreatic injury in PD-1-deficient mice than in control mice, including increased pancreatic edema, inflammatory cells, infiltration, and acinar cell necrosis. We also found that PD-1-deficient mice exhibited higher levels of serum enzymology and inflammatory factors in AP. Furthermore, PD-1/PDL1 neutralizing antibodies significantly aggravated pancreatic and lung injury and increased serum inflammatory cytokine levels. These findings were consistent with those in PD-1-deficient mice. In summary, PD-1 may protect against AP in mice and act as a potential target for the prevention of AP in the future.

PD-1 Regulates GABAergic Neurotransmission and GABA-Mediated Analgesia and Anesthesia.

SummaryThe immune checkpoint inhibitor programmed cell death protein 1 (PD-1) plays a critical role in immune regulation. Recent studies have demonstrated functional PD-1 expression in peripheral sensory neurons, which contributes to neuronal excitability, pain, and opioid analgesia. Here we report neuronal expression and function of PD-1 in the central nervous system (CNS), including the spinal cord, thalamus, and cerebral cortex. Notably, GABA-induced currents in spinal dorsal horn neurons, thalamic neurons, and cortical neurons are suppressed by the PD-1-neutralizing immunotherapeutic Nivolumab in spinal cord slices, brain slices, and dissociated cortical neurons. Reductions in GABA-mediated currents in CNS neurons were also observed in Pd1−/− mice without changes in GABA receptor expression. Mechanistically, Nivolumab binds spinal cord neurons and elicits ERK phosphorylation to suppress GABA currents. Finally, both GABA-mediated analgesia and anesthesia are impaired by Pd1 deficiency. Our findings reveal PD-1 as a CNS-neuronal inhibitor that regulates GABAergic signaling and GABA-mediated behaviors.

PD-1 pathway regulates ILC2 metabolism and PD-1 agonist treatment ameliorates airway hyperreactivity

Allergic asthma is a leading chronic disease associated with airway hyperreactivity (AHR). Type-2 innate lymphoid cells (ILC2s) are a potent source of T-helper 2 (Th2) cytokines that promote AHR and lung inflammation. As the programmed cell death protein-1 (PD-1) inhibitory axis regulates a variety of immune responses, here we investigate PD-1 function in pulmonary ILC2s during IL-33-induced airway inflammation. PD-1 limits the viability of ILC2s and downregulates their effector functions. Additionally, PD-1 deficiency shifts ILC2 metabolism toward glycolysis, glutaminolysis and methionine catabolism. PD-1 thus acts as a metabolic checkpoint in ILC2s, affecting cellular activation and proliferation. As the blockade of PD-1 exacerbates AHR, we also develop a human PD-1 agonist and show that it can ameliorate AHR and suppresses lung inflammation in a humanized mouse model. Together, these results highlight the importance of PD-1 agonistic treatment in allergic asthma and underscore its therapeutic potential.

PD-1 blockade inhibits osteoclast formation and murine bone cancer pain.

Emerging immune therapy, such as with the anti-programmed cell death-1 (anti-PD-1) monoclonal antibody nivolumab, has shown efficacy in tumor suppression. Patients with terminal cancer suffer from cancer pain as a result of bone metastasis and bone destruction, but how PD-1 blockade affects bone cancer pain remains unknown. Here, we report that mice lacking Pdcd1 (Pd1-/-) demonstrated remarkable protection against bone destruction induced by femoral inoculation of Lewis lung cancer cells. Compared with WT mice, Pd1-/- mice exhibited increased baseline pain sensitivity, but the development of bone cancer pain was compromised in Pd1-/- mice. Consistently, these beneficial effects in Pd1-/- mice were recapitulated by repeated i.v. applications of nivolumab in WT mice, even though nivolumab initially increased mechanical and thermal pain. Notably, PD-1 deficiency or nivolumab treatment inhibited osteoclastogenesis without altering tumor burden. PD-L1 and CCL2 are upregulated within the local tumor microenvironment, and PD-L1 promoted RANKL-induced osteoclastogenesis through JNK activation and CCL2 secretion. Bone cancer upregulated CCR2 in primary sensory neurons, and CCR2 antagonism effectively reduced bone cancer pain. Our findings suggest that, despite a transient increase in pain sensitivity following each treatment, anti-PD-1 immunotherapy could produce long-term benefits in preventing bone destruction and alleviating bone cancer pain by suppressing osteoclastogenesis.

Blockade of CD80 interaction with PD-L1 between T and tumor cells augments effector T expansion and tumor immunity in a PD-1-dependent manner

Abstract PD-L1 interactions with PD-1 and CD80 play a critical role in regulating tumor immunity. Blockade of PD-L1 interaction with PD-1 between tumor and T cells augments tumor immunity. Cis-PD-L1/CD80 interactions reduce PD-L1 interaction with PD-1 on T cells and augment tumor immunity. However, whether trans-PD-L1 interaction with CD80 between tumor and T cells play a role in regulating tumor immunity remains unknown. In the current studies, using B16 and MC38 tumor lines in C57BL/6 mice with or without PD-1 or PD-L1 deficiency, we show that administration of anti-PD-L1 (43H12), a monoclonal antibody that specifically blocks PD-L1 interaction with CD80, augments tumor immunity. The effect is tumor PD-L1 interaction with PD-1 on T cells-dependent, because although 43H12 blockade does not augment tumor immunity in PD-1−/− mice or in PD-L1−/− mice with PD-L1 KO tumor lines, 43H12 blockade does augment tumor immunity in PD-L1−/− mice with wild-type tumor lines. Furthermore, consistent with CD28 requirement for augmenting anti-tumor immunity during blocking anti-PD-1 treatment, 43H12 blockade of PD-L1/CD80 interaction does not augment tumor immunity in CD28−/− mice. Finally, 43H12 blockade augments CD8+ T effector expansion in the tumor draining lymph nodes, with increased production of IFN-g and down-regulation of ps21-EZH2. These results indicate that blockade of PD-L1 interaction with CD80 can augment tumor immunity via down-regulating the effect of PD-L1 interaction with PD-1. (This work is supported by DMRI institutional funds and NIH 1R01CA228465-01 to Zeng).

Pembrolizumab and Copanlisib for the Treatment of Relapsed or Refractory Mature T-Cell Lymphomas

Pembrolizumab and Copanlisib for the Treatment of Relapsed or Refractory Mature T-Cell Lymphomas