Unleashing PD-1: a duel of immunity in aortic aneurysm formation.

Aortic aneurysms, particularly abdominal aortic aneurysms (AAAs), exhibit sex differences, with higher prevalence and severity in males than females, both in humans and experimental mouse models. In fact, male sex has been considered as the most potent nonmodifiable risk factor for AAA. Currently, there are no medications approved for the treatment of aortic aneurysms, despite the high lethality of ruptured aneurysms, which account for nearly 2% of all deaths. Moreover, the underlying molecular mechanisms mediating the sexual dimorphism of aortic aneurysms remain largely unknown. In this issue of the JCI, Mu et al. revealed a mechanism by which androgens, male sex hormones, exacerbate aortic aneurysms by suppressing programmed cell death protein 1 (PD-1) expression in T cells in an aldosterone and high salt-induced aortic aneurysm mouse model.

Single-cell resolution characterization of myeloid-derived cell states with implication in cancer outcome.

Tumor-associated myeloid-derived cells (MDCs) significantly impact cancer prognosis and treatment responses due to their remarkable plasticity and tumorigenic behaviors. Here, we integrate single-cell RNA-sequencing data from different cancer types, identifying 29 MDC subpopulations within the tumor microenvironment. Our analysis reveals abnormally expanded MDC subpopulations across various tumors and distinguishes cell states that have often been grouped together, such as TREM2+ and FOLR2+ subpopulations. Using deconvolution approaches, we identify five subpopulations as independent prognostic markers, including states co-expressing TREM2 and PD-1, and FOLR2 and PDL-2. Additionally, TREM2 alone does not reliably predict cancer prognosis, as other TREM2+ macrophages show varied associations with prognosis depending on local cues. Validation in independent cohorts confirms that FOLR2-expressing macrophages correlate with poor clinical outcomes in ovarian and triple-negative breast cancers. This comprehensive MDC atlas offers valuable insights and a foundation for futher analyses, advancing strategies for treating solid cancers.

Expression of programmed cell death protein 1 and programmed cell death ligand 1 in feline injection site fibrosarcomas.

Feline injection site fibrosarcomas represent a unique challenge in veterinary oncology due to their association with injection sites and aggressive behaviour. The study explores the expression of immune checkpoints programmed cell death protein 1 and programmed cell death ligand 1 in the malignancy, aiming to unravel their potential significance in tumour progression. The study included 31, archival diagnostic specimens of feline fibrosarcomas, located in the common injection sites. The programmed cell death protein 1 and programmed cell death ligand 1 expression in tumour cells and tumour infiltrating lymphocytes were assessed by immunohistochemical methods. Programmed cell death protein 1 and programmed cell death ligand 1 expression were observed in 84% and 81% of cases, respectively. In tumour infiltrating lymphocytes the PD-1 expression was observed in 71% of cases. Notably, higher programmed cell death protein 1 expression correlated with tumour grade and heightened inflammation score, suggesting a potential association with tumour aggressiveness. Similarly, programmed cell death ligand 1 expression exhibited a positive correlation with tumour grade and inflammation score. The observed findings suggest a potential role for programmed cell death protein 1 and programmed cell death ligand 1 in tumour progression and immune response within the tumour microenvironment. Moreover, this study contributes to a deeper understanding of feline injection site fibrosarcoma pathogenesis, emphasizing the importance of considering immunological perspectives in developing effective treatment strategies for this challenging condition. Further investigations are warranted to advance our knowledge and refine therapeutic approaches for feline injection site fibrosarcoma management.

Spore Oil enhances the effect of cyclophosphamide inhibiting programmed death-1 and prolongs the survival of H22 tumor-bearing mice.

OBJECTIVE: To investigate the effect of Ganoderma Lucidum Spore Oil (GLSO) on the tumor growth and survival of H22 tumor-bearing mice treated with cyclophosphamide (CTX), and explore the underlying mechanism. METHODS: Allograft H22 hepatocellular carcinoma mouse model was applied to investigate the effect of GLSO on the tumor growth and survival of animals, and Kaplan-Meier survival analysis was used to analyze the life span. Plasma biochemical examination was used to determine the levels of alanine aminotransferase (ALT), aspartate aminotransferase (AST), urea (UREA) and creatinine (CRE). Western blot analysis was performed to detect Programmed Death-1 (PD-1), Programmed Death Ligand 1 (PD-L1), Janus Kinase 2 (JAK2), phosphorylated Signal Transducer and Activator of Transcription 3 (p-STAT3), and Signal Transducer and Activator of Transcription 3 (STAT3) expression. RESULTS: GLSO increased the anti-tumor effect of CTX and prolonged the survival of H22 tumor-bearing mice treated with CTX. Meanwhile, GLSO increased the thymus index and showed no obvious toxicity to liver functions of animals. GLSO also decreased the level of UREA in H22 tumor-bearing mice treated with CTX. Furthermore, GLSO could inhibit the expression of PD-1 in spleen, which was independent of JAK2 expression and STAT3 phosphorylation. However, GLSO did not affect the expression of PD-L1, JAK2, and p-STAT3 in tumor tissue. CONCLUSION: GLSO could strengthen the anti-tumor effect of CTX and prolong the life span of H22 tumor-bearing mice, while the underlying mechanism might be relevant to the amelioration effect of thymus function and inhibition of PD-1 expression in spleen. Furthermore, these findings implied the promising role of GLSO in combination with CTX to extend the survival of patients in clinical chemotherapy of hepatocellular carcinoma.

Miniprotein engineering for inhibition of PD-1/PD-L1 interaction.

Miniproteins constitute an excellent basis for the development of structurally demanding functional molecules. The engrailed homeodomain, a three-helix-containing miniprotein, was applied as a scaffold for constructing programmed cell death protein 1/programmed death-ligand 1 (PD-1/PD-L1) interaction inhibitors. PD-L1 binders were initially designed using the computer-aided approach and subsequently optimized iteratively. The conformational stability was assessed for each obtained miniprotein using circular dichroism spectroscopy, indicating that numerous mutations could be introduced. The formation of a sizable hydrophobic surface at the inhibitor that fits the molecular target imposed the necessity for the incorporation of additional charged amino acid residues to retain its appropriate solubility. Finally, the miniprotein effectively binding to PD-L1 (KD = 51.4 nM) that inhibits PD-1/PD-L1 interaction in cell-based studies with EC50 = 3.9 µM, was discovered.

Single-Cell Analysis Reveals That CD47 mRNA Expression Correlates with Immune Cell Activation, Antiviral Isgs, and Cytotoxicity.

BACKGROUND/AIMS: Immune cells are reported to upregulate CD47 during infection, however, the role of CD47 in innate and adaptive immune cells remains unclear. METHODS: To bridge this knowledge gap, we analysed our single cell (sc)-RNA dataset along with other publicly available sc-RNA datasets from healthy controls, people with HIV-1 (PWH) and COVID-19 patients. We characterized each immune cell based on low, intermediate, and high expression of CD47 . RESULTS: Our analyses revealed that CD47 high pDCs and monocytes exhibited relatively higher expression of IFN-α regulatory genes, antiviral interferon-stimulated genes (ISGs) and MHC-I associated genes compared to CD47 inter. and CD47 low cells. Furthermore, CD47 high NK and CD8+ T cells showed higher expression of antiviral ISGs, as well as genes encoding for cytotoxic markers like granzyme B, perforin, granulysin, interferon gamma and NKG7. Additionally, CD47 high CD8+ T cells expressed higher levels of PD-1 and LAG-3 genes. Lastly, we found that CD47 high B cells had enriched expression of genes involved in cell activation and humoral responses. CONCLUSION: Overall, our analyses revealed that innate and adaptive immune cells expressing elevated activation and functional gene signatures also express higher CD47 levels.

Type I Interferon Activates PD-1 Expression through Activation of the STAT1-IRF2 Pathway in Myeloid Cells.

PD-1 (Programmed cell death protein 1) regulates the metabolic reprogramming of myeloid-derived suppressor cells and myeloid cell differentiation, as well as the type I interferon (IFN-I) signaling pathway in myeloid cells in the tumor microenvironment. PD-1, therefore, is a key inhibitory receptor in myeloid cells. However, the regulation of PD-1 expression in myeloid cells is unknown. We report that the expression level of PDCD1, the gene that encodes the PD-1 protein, is positively correlated with the levels of IFNB1 and IFNAR1 in myeloid cells in human colorectal cancer. Treatment of mouse myeloid cell lines with recombinant IFNß protein elevated PD-1 expression in myeloid cells in vitro. Knocking out IFNAR1, the gene that encodes the IFN-I-specific receptor, diminished the inductive effect of IFNß on PD-1 expression in myeloid cells in vitro. Treatment of tumor-bearing mice with a lipid nanoparticle-encapsulated IFNß-encoding plasmid (IFNBCOL01) increased IFNß expression, resulting in elevated PD-1 expression in tumor-infiltrating myeloid cells. At the molecular level, we determined that IFNß activates STAT1 (signal transducer and activator of transcription 1) and IRFs (interferon regulatory factors) in myeloid cells. Analysis of the cd279 promoter identified IRF2-binding consensus sequence elements. ChIP (chromatin immunoprecipitation) analysis determined that the pSTAT1 directly binds to the irf2 promoter and that IRF2 directly binds to the cd279 promoter in myeloid cells in vitro and in vivo. In colon cancer patients, the expression levels of STAT1, IRF2 and PDCD1 are positively correlated in tumor-infiltrating myeloid cells. Our findings determine that IFNß activates PD-1 expression at least in part by an autocrine mechanism via the stimulation of the pSTAT1-IRF2 axis in myeloid cells.

Differential impact of genetic deletion of TIGIT or PD-1 on melanoma-specific T-lymphocytes.

Immune checkpoint (IC) blockade and adoptive transfer of tumor-specific T-cells (ACT) are two major strategies to treat metastatic melanoma. Their combination can potentiate T-cell activation in the suppressive tumor microenvironment, but the autoimmune adverse effects associated with systemic injection of IC blockers persist with this strategy. ACT of tumor-reactive T-cells defective for IC expression would overcome this issue. For this purpose, PD-1 and TIGIT appear to be relevant candidates, because their co-expression on highly tumor-reactive lymphocytes limits their therapeutic efficacy within the tumor microenvironme,nt. Our study compares the consequences of PDCD1 or TIGIT genetic deletion on anti-tumor properties and T-cell fitness of melanoma-specific T lymphocytes. Transcriptomic analyses revealed down-regulation of cell cycle-related genes in PD-1KO T-cells, consistent with biological observations, whereas proliferative pathways were preserved in TIGITKO T-cells. Functional analyses showed that PD-1KO and TIGITKO T-cells displayed superior antitumor reactivity than their wild-type counterpart in vitro and in a preclinical melanoma model using immunodeficient mice. Interestingly, it appears that TIGITKO T-cells were more effective at inhibiting tumor cell proliferation in vivo, and persist longer within tumors than PD-1KO T-cells, consistent with the absence of impact of TIGIT deletion on T-cell fitness. Taken together, these results suggest that TIGIT deletion, over PD-1 deletion, in melanoma-specific T-cells is a compelling option for future immunotherapeutic strategies.

Protocol for Efficient Generation of Chimeric Antigen Receptor T Cells with Multiplexed Gene Silencing by Epigenome Editing.

Multiplex gene regulation enables the controlled and simultaneous alteration of the expression levels of multiple genes and is generally pursued to precisely alter complex cellular pathways with a single intervention. Thus far, this has been typically exploited in combination with genome editing tools (i.e., base-/prime-editing, designer nucleases) to enable simultaneous genetic alterations and modulate complex physiologic cellular pathways. In the field of cancer immunotherapy, multiplex genome editing has been used to simultaneously inactivate three genes (i.e., TRAC, B2M, and PDCD1) and generate universal chimeric antigen receptor (CAR) T cells resistant to the inhibitory activity of the PD-1 ligand. However, the intrinsic risk of genomic aberrations driven by such tools poses concerns because of the generation of multiple single-strand or double-strand DNA breaks followed by DNA repair. Modulating gene expression without DNA damage using epigenome editing promises a safer and efficient approach to alter gene expression. This method enables for simultaneous activation and/or repression of target genes, offering superior fine-tuning capabilities with reduced off-targeting effects and potential reversibility as compared to genome editing. Here we describe a detailed protocol for achieving multiplexed and sustainable gene silencing in CAR T cells. In an exemplary approach, we use designer epigenome modifiers (DEMs) for the simultaneous inactivation of two T cell inhibitory genes, PDCD1 and LAG3 to generate CAR T cells with increased resistance to tumor-induced exhaustion.

[Terminalia chebula water extract reduces joint inflammation by regulating cellular immunity in spleen cells of collagen-induced arthritis (CIA) rats through up-regulation of PD-1/PD-L1].

Objective To investigate the effect of Terminalia chebula water extract (TCWE) on the cellular immunity and PD-1/PD-L1 pathway in rats with collagen-induced arthritis (CIA). Methods SD rats were randomly divided into four groups: a control group, a CIA group, a TCWE group and a methotrexate (MTX) group, with 15 rats in each group. Except for the control group, SD rats in other groups were subcutaneously injected with type II collagen to establish the model of collagen-induced arthritis (CIA). The rats in the TCWE group were treated with 20 mg/(kg.d) TCWE and the rats in the MTX group were treated with 1.67 mg/(kg.d) MTX. After 14 days of treatment, the cartilage morphology was examined using hematoxylin-eosin (HE) staining, and splenic T lymphocyte apoptosis and Treg/Th17 cell ratio were detected by flow cytometry. The mRNA expressions of retinoid-related orphan nuclear receptor γt (RORγt), forkhead box P3 (FOXP3), PD-1 and PD-L1 in spleen were detected by reverse transcription PCR. The expression and localization of RORγt and FOXP3 were detected by immunohistochemical staining. The protein expressions of PD-1 and PD-L1 in splenic lymphocytes were detected by Western blot, and the levels of serum interleukin 17 (IL-17) and transforming growth factor ß (TGF-ß) in rats were detected by ELISA. Results Compared with CIA group, the pathological changes of cartilage and synovium were significantly alleviated in the TCWE group and the MTX group. Both the apoptosis rate of T lymphocytes in spleen and the ratio of Treg/Th17 cells increased. The expression of RORγt decreased, while the expressions of FOXP3, PD-1 and PD-L1 increased in spleen lymphocytes. The level of serum IL-17 decreased, while the level of serum TGF-ß increased. Conclusion TCWE treatment may activate PD-1/PD-L1 pathway in spleen cells to regulate cellular immunity, thus reducing cartilage injury in CIA rats.

Interconnected lineage trajectories link conventional and natural killer (NK)-like exhausted CD8+ T cells beneficial in type 1 diabetes.

Distinct Natural Killer (NK)-like CD57+ and PD-1+ CD8+ exhausted-like T cell populations (Tex) have both been linked to beneficial immunotherapy response in autoimmune type 1 diabetes (T1D) patients. The origins and relationships between these cell types are poorly understood. Here we show that while PD-1+ and CD57+ Tex populations are epigenetically similar, CD57+ Tex cells display unique increased chromatin accessibility of inhibitory Killer Cell Immunoglobulin-like Receptor (iKIR) and other NK cell genes. PD-1+ and CD57+ Tex also show reciprocal expression of Inhibitory Receptors (IRs) and iKIRs accompanied by chromatin accessibility of Tcf1 and Tbet transcription factor target sites, respectively. CD57+ Tex show unappreciated gene expression heterogeneity and share clonal relationships with PD-1+ Tex, with these cells differentiating along four interconnected lineage trajectories: Tex-PD-1+, Tex-CD57+, Tex-Branching, and Tex-Fluid. Our findings demonstrate new relationships between Tex-like populations in human autoimmune disease and suggest that modulating common precursor populations may enhance response to autoimmune disease treatment.

Changes in T-cell subsets occur in interstitial lung disease and may contribute to pathology via complicated immune cascade.

The study aimed to investigate the expression profiles of transcription factors, cytokines, and co-stimulatory molecules in helper T (Th)-cell subsets within bronchoalveolar lavage (BAL) samples of patients with interstitial lung diseases (ILDs). Twenty ILDs patients were included in the study, comprising those with idiopathic pulmonary fibrosis (IPF) (n:8), autoimmune-related ILDs (auto-ILD) (n:4), and orphan diseases (O-ILD) (n:8), alongside five control subjects. Flow cytometry was employed to evaluate the Th to cytotoxic T cell (CTL) ratio in BAL fluid, while cytopathological examination assessed macrophages, lymphocytes, and neutrophils. Quantitative real-time polymerase chain reaction was utilized to investigate the expressions in Th1, Th2, Th17, and regulatory T (Treg) cells. Results revealed elevated Th cell to CTL ratios across all patient groups compared to controls. Furthermore, upregulation of Th1, Th2, Th17, and T-cell factors was observed in all patient groups compared to controls. Interestingly, upregulation of CD28 and downregulation of CTLA-4 and PD-1 gene expression were consistent across all ILDs groups, highlighting potential immune dysregulation. This study provides a comprehensive exploration of molecular immunological mechanisms in ILDs patients, underscoring the dominance of Th2 and Th17 responses and revealing novel findings regarding the dysregulation of CD28, CTLA-4, and PD-1 expressions in ILDs for the first time.

PD-1/PD-L1 Provides Protective Role in Hypoxia-Induced Pulmonary Vascular Remodeling.

BACKGROUND: Hypoxia-induced pulmonary hypertension (HPH) is a T helper 17 cell response-driven disease, and PD-1 (programmed cell death 1)/PD-L1 (programmed cell death-ligand 1) inhibitor-associated pulmonary hypertension has been reported recently. This study is designed to explore whether the PD-1/PD-L1 pathway participates in HPH via regulating endothelial dysfunction and T helper 17 cell response. METHODS: Lung tissue samples were obtained from eligible patients. Western blotting, immunohistochemistry, and immunofluorescence techniques were used to assess protein expression, while immunoprecipitation was utilized to detect ubiquitination. HPH models were established in C57BL/6 WT (wild-type) and PD-1-/- mice, followed by treatment with PD-L1 recombinant protein. Adeno-associated virus vector delivery was used to upregulate PD-L1 in the endothelial cells. Endothelial cell function was assessed through assays for cell angiogenesis and adhesion. RESULTS: Expression of the PD-1/PD-L1 pathway was downregulated in patients with HPH and mouse models, with a notable decrease in PD-L1 expression in endothelial cells compared with the normoxia group. In comparison to WT mice, PD-1-/- mice exhibited a more severe HPH phenotype following exposure to hypoxia, However, administration of PD-L1 recombinant protein and overexpression of PD-L1 in lung endothelial cells mitigated HPH. In vitro, blockade of PD-L1 with a neutralizing antibody promoted endothelial cell angiogenesis, adhesion, and pyroptosis. Mechanistically, hypoxia downregulated PD-L1 protein expression through ubiquitination. Additionally, both in vivo and in vitro, PD-L1 inhibited T helper 17 cell response through the PI3K (phosphoinositide 3-kinase)/AKT (protein kinase B)/mTOR (mammalian target of rapamycin) pathway in HPH. CONCLUSIONS: PD-1/PD-L1 plays a role in ameliorating HPH development by inhibiting T helper 17 cell response through the PI3K/AKT/mTOR pathway and improving endothelial dysfunction, suggesting a novel therapeutic indication for PD-1/PD-L1-based immunomodulatory therapies in the treatment of HPH.

Androgen aggravates aortic aneurysms via suppression of PD-1 in mice.

Androgen has long been recognized for its pivotal role in the sexual dimorphism of cardiovascular diseases, including aortic aneurysms (AAs), a devastating vascular disease with a higher prevalence and fatality rate in men than in women. However, the mechanism by which androgen mediates AAs is largely unknown. Here, we found that male, not female, mice developed AAs when exposed to aldosterone and high salt (Aldo-salt). We revealed that androgen and androgen receptors (ARs) were crucial for this sexually dimorphic response to Aldo-salt. We identified programmed cell death protein 1 (PD-1), an immune checkpoint, as a key link between androgen and AAs. Furthermore, we demonstrated that administration of anti-PD-1 Ab and adoptive PD-1-deficient T cell transfer reinstated Aldo-salt-induced AAs in orchiectomized mice and that genetic deletion of PD-1 exacerbated AAs induced by a high-fat diet and angiotensin II (Ang II) in nonorchiectomized mice. Mechanistically, we discovered that the AR bound to the PD-1 promoter to suppress the expression of PD-1 in the spleen. Thus, our study unveils a mechanism by which androgen aggravates AAs by suppressing PD-1 expression in T cells. Moreover, our study suggests that some patients with cancer might benefit from screenings for AAs during immune checkpoint therapy.

Relationship Between Cytotoxic T-Lymphocyte-associated Antigen-4: Programmed Death-1 Genes Polymorphisms and Susceptibility to Pediatric B-Cell Acute Lymphoblastic Leukemia.

Programmed death-1 (PD1) and cytotoxic T-lymphocyte-associated antigen 4 (CTLA-4) have a vital role in immune checkpoint pathways. Single nucleotide polymorphisms (SNPs) of PD1 and CTLA4 have been reported to be associated with susceptibility to certain autoimmune diseases and cancers. The potential association between SNPs in these immune checkpoint genes and risk of acute lymphoblastic leukemia (ALL) still unclear. The aim of this study is to clarify the effect of PD1 and CTLA4 SNPs on the risk of developing ALL and the prognosis of the disease. The study was performed on 100 pediatric B-ALL patients and 100 controls. The PD1 and CTLA4 SNPs were examined by RFLP technique. The study revealed that CTLA4 (rs11571316) was associated with high risk of B-ALL developments OR 1.492 (CI: 1157 to 1924) ( P =0.002). PD1 (rs36084323) GA genotype was significantly associated with protective effect against nonremission ( P =0.007). PD1 (rs36084323) A allele were associated with protective effect against relapse ( P =0.008). CTLA4 and PD1 genotypes did not have significant impact on B-ALL patients outcome. The current study displayed for the first time that genetic variations of the CTLA-4, was associated with susceptibility to B-ALL and that PD1 (rs36084323) GA genotype was significantly associated with protective effect against nonremission, while PD1 (rs36084323) A allele was associated with protective effect against relapse.

CD8+ T cell-derived Fgl2 regulates immunity in a cell-autonomous manner via ligation of FcγRIIB.

The regulatory circuits dictating CD8+ T cell responsiveness versus exhaustion during anti-tumor immunity are incompletely understood. Here we report that tumor-infiltrating antigen-specific PD-1+ TCF-1- CD8+ T cells express the immunosuppressive cytokine Fgl2. Conditional deletion of Fgl2 specifically in mouse antigen-specific CD8+ T cells prolongs CD8+ T cell persistence, suppresses phenotypic and transcriptomic signatures of T cell exhaustion, and improves control of the tumor. In a mouse model of chronic viral infection, PD-1+ CD8+ T cell-derived Fgl2 also negatively regulates virus-specific T cell responses. In humans, CD8+ T cell-derived Fgl2 is associated with poorer survival in patients with melanoma. Mechanistically, the dampened responsiveness of WT Fgl2-expressing CD8+ T cells, when compared to Fgl2-deficient CD8+ T cells, is underpinned by the cell-intrinsic interaction of Fgl2 with CD8+ T cell-expressed FcγRIIB and concomitant caspase 3/7-mediated apoptosis. Our results thus illuminate a cell-autonomous regulatory axis by which PD-1+ CD8+ T cells both express the receptor and secrete its ligand in order to mediate suppression of anti-tumor and anti-viral immunity.

Evaluation of PD-1 Gene Expression Profile and Methylation of the Regulatory Regions in Patients with Ankylosing Spondylitis.

Background: Ankylosing spondylitis (AS) is a chronic autoimmune disorder characterized by the fusion of vertebral joints and axial arthritis. The programmed death-1 (PD-1) inhibitory receptor has a pivotal role in controlling T cell function and may have a significant impact on the pathogenesis of autoimmune diseases such as AS pathogenesis. Objective: To investigate PD-1 gene expression and its epigenetic regulation by detecting methylated CpG islands in the regulatory sites of the gene. This will provide insight into the mechanisms involved in the disease. Methods: 30 AS patients and 30 healthy individuals were examined to detect the 16 CpG islands in intron 1 using bisulfite conversion and methylation-specific PCR technique. In addition, RNA samples were isolated from fresh peripheral blood mononuclear cells (PBMCs), and after complementary DNA (cDNA) synthesis, the expression level of the PD-1 gene was evaluated using Real-Time PCR. Results: The CpG islands located in the intronic zone of the PD-1 gene were hyper-methylated in both the patients with AS and the healthy controls. The gene expression of PD-1 was significantly downregulated in AS patients compared with the controls (p=0.017). A negative correlation between the Bath Ankylosing Spondylitis Disease Activity Index and PD-1 gene expression was also revealed. Conclusion: The low level of PD-1 gene expression is implicated in the pathogenesis of AS. However, in both groups, the methylation level of the intron 1 CpG islands of the PD-1 gene suggests that other regulatory mechanisms are more relevant to PD-1 gene expression than methylation in the intron.

IRF4 impedes human CD8 T cell function and promotes cell proliferation and PD-1 expression.

Human CD8 tumor-infiltrating lymphocytes (TILs) with impaired effector functions and PD-1 expression are categorized as exhausted. However, the exhaustion-like features reported in TILs might stem from their activation rather than the consequence of T cell exhaustion itself. Using CRISPR-Cas9 and lentiviral overexpression in CD8 T cells from non-cancerous donors, we show that the T cell receptor (TCR)-induced transcription factor interferon regulatory factor 4 (IRF4) promotes cell proliferation and PD-1 expression and hampers effector functions and expression of nuclear factor κB (NF-κB)-regulated genes. While CD8 TILs with impaired interferon γ (IFNγ) production exhibit activation markers IRF4 and CD137 and exhaustion markers thymocyte selection associated high mobility group box (TOX) and PD-1, activated T cells in patients with COVID-19 do not demonstrate elevated levels of TOX and PD-1. These results confirm that IRF4+ TILs are exhausted rather than solely activated. Our study indicates, however, that PD-1 expression, low IFNγ production, and active cycling in TILs are all influenced by IRF4 upregulation after T cell activation.

Association between PD-1 single nucleotide gene variants and the risk of metastatic melanoma.

Previous studies showed an association between single nucleotide gene variants (SNVs) of PD-1 and cancer susceptibility. We analyzed PD1.5 C > T and PD1.7 T > C SNVs to investigate their association with the risk of developing metastatic melanoma (MM). Utilizing a cohort of 125 MM patients treated with anti-PD-1 agents and 84 healthy controls, we examined genotype/allele frequencies through a modified Poisson regression model, adjusted for age and sex. Our findings indicate that the PD1.5 T allele is associated with a reduced risk of MM, showing a significantly lower risk in both codominant (RR = 0.56, 95%CL: 0.37-0.87) and dominant (RR = 0.73 95%CL: 0.59-0.90) models. Conversely, the PD1.7 C allele is linked to an increased risk of MM, with the C/C genotype exhibiting a higher risk in the codominant (RR = 1.65, 95%CL: 1.32-2.05) and allelic (RR = 1.23, 95%CL: 1.06-1.43) models. These results are consistent with previous meta-analyses on other cancer types, mainly highlighting the PD1.5 SNV's potential role in promoting anti-tumor immunity through increased PD1-positive circulating effector T cell activity.