PDCD1: a tissue-specific susceptibility locus for inherited inflammatory disorders

Associations of PD-1 and PD-L1 gene polymorphisms with cancer risk: a meta-analysis based on 50 studies

Programmed death-1 and its ligand-1 (PD-1/PD-L1), immune checkpoints proteins, play a crucial role in anti-tumor responses. A large number of studies have evaluated the relationships of PD-1/PD-L1 polymorphisms with risk of cancer, but evidence for the associations remains inconsistent. Therefore, we performed a meta-analysis to examine the associations between PD-1/PD-L1 single nucleotide polymorphisms (SNPs) and cancer predisposition. Results showed that PD-1.3 and PD-L1 rs17718883 were significantly correlated with overall cancer risk. PD-1.5 was prominently linked with cervical cancer (CC), non-small cell lung cancer (NSCLC), TC (thyroid cancer), brain tumor, AML (acute myelocytic leukemia) and UCC (urothelial cell carcinoma) risk, PD-1.9 with breast cancer (BC), AML, esophageal cancer (EC) and ovarian cancer (OC) risk, and PD-1.3 with colorectal cancer (CRC) and BCC (basal cell carcinoma) risk. PD-1.1 polymorphism slightly elevated BC and OC susceptibility, whereas the rs4143815 variant notably decreased the risk of gastric cancer (GC), hepatocellular carcinoma (HCC) and OC, but increased the risk of BC. PD-1.6 was closely linked with AML risk, PD-L1 rs2890658 with NSCLC, HCC and BC risk, rs17718883 with HCC and GC risk, rs10815225 with GC risk, and rs2297136 with NSCLC and HCC risk. Interestingly, the rs7421861, rs10815225, and rs10815225 markedly reduced cancer susceptibility among Asians. The rs7421861 polymrophism decreased cancer risk among Caucasians, rather than the rs10815225 elevated cancer risk. Our results supported that PD-1 and PD-L1 SNPs were dramatically correlated with cancer risk.

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

BACKGROUND

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.

OBJECTIVE

We sought to investigate the role of PD-1 in the regulation of acute neutrophilic inflammation in a murine model of airway hyperreactivity (AHR).

METHODS

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.

RESULTS

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.

CONCLUSIONS

PD-1 agonist treatment is efficient in dampening neutrophilic AHR and lung inflammation in a preclinical humanized mouse model.

Comprehensive analysis about prognostic and immunological role of WTAP in pan-cancer

Background: Wilms tumor 1-associated protein (WTAP) plays a critical role in ribonucleic acid (RNA) methylation of N6 adenosine (m⁶A) modification, which is closely related with varieties of biological process. However, the role of WTAP in cancers remains to be determined. This study is designed to demonstrate the prognostic landscape of WTAP in pan-cancer and explore the relationship between WTAP expression and immune infiltration.

Methods: Here, we investigated the expression level and prognostic role of WTAP in pan-cancer using multiple databases, including PrognoScan, GEPIA, and Kaplan-Meier Plotter. Then, applying the GEPIA and TIMER databases, we illustrated the correlations between WTAP expression and immune infiltration in tumors, especially liver hepatocellular carcinoma (LIHC), and esophageal carcinoma (ESCA).

Results: WTAP had significant higher expression levels in tumor tissues of ESCA, LIHC, etc., while lower expression levels in those of bladder urothelial carcinoma (BLCA), breast invasive carcinoma (BRCA), etc. And WTAP demonstrated multifaceted prognostic value in cancers. Of our interests, WTAP exerted a harmful effect on LIHC patient for overall survival (OS) and progression free survival (PFS). WTAP expression also significantly associated with the infiltration levels of B cells, CD8⁺ T cells, CD4⁺ T cells, macrophages, neutrophils, and dendritic cells (DC) in LIHC but not ESCA. Furthermore, combined analysis about WTAP expression level and immune cell specific gene markers implied WTAP correlates with regulatory cells (T reg) infiltration in LIHC and ESCA.

Conclusion: The m⁶A regulator WTAP can serve as a prognostic biomarker for certain tumor types in pan-cancer and potentially result from immune cell infiltration.

Bridging the Gap: Connecting the Mechanisms of Immune-Related Adverse Events and Autoimmunity Through PD-1

The emergence of anti-cytotoxic T-lymphocyte antigen 4 (anti-CTLA-4), anti-programmed cell death 1 ligand (anti-PD-1), and anti-PD-L1 antibodies as immune checkpoint inhibitors (ICIs) revolutionized the treatment of numerous types of tumors. These antibodies, both alone and in combination, provide great clinical efficacy as evidenced by tumor regression and increased overall patients' survival. However, with this success comes multiple challenges. First, while patients who respond to ICIs have outstanding outcomes, there remains a large proportion of patients who do not respond at all. This all-or-none response has led to looking downstream of programmed cell death 1 (PD-1) for additional therapeutic targets and for new combination therapies. Second, a majority of patients who receive ICIs go on to develop immune-related adverse events (irAEs) characterized by end-organ inflammation with T-cell infiltrates. The hallmarks of these clinically observed irAEs share many similarities with primary autoimmune diseases. The contribution of PD-1 to peripheral tolerance is a major mechanism for protection against expansion of self-reactive T-cell clones and autoimmune disease. In this review, we aim to bridge the gaps between our cellular and molecular knowledge of PD-1 signaling in T cells, ICI-induced irAEs, and autoimmune diseases. We will highlight shared mechanisms and the potential for new therapeutic strategies.

Transcriptional and epigenetic regulation of PD-1 expression

Programmed cell death-1 (PD-1) is a co-inhibitory receptor that plays important roles in regulating T cell immunity and peripheral tolerance. PD-1 signaling prevents T cells from overactivation during acute infections, but it maintains T cell exhaustion during chronic infections. Tumor cells can exploit the PD-1 signaling pathway to evade antitumor immune responses. The PD-1 signaling pathway is also essential for maintaining peripheral tolerance and prevention of autoimmunity. PD-1 expression is strictly and differentially regulated by diverse mechanisms in immune cells. It is activated and repressed by distinct transcription factors in different circumstances. Moreover, epigenetic mechanisms are also involved in regulating PD-1 expression. In this review, we summarize the knowledge of the transcriptional and epigenetic regulation of PD-1 expression during different immune responses.

SAP interacts with CD28 to inhibit PD-1 signaling in T lymphocytes

T cell co-stimulation is important for the maintenance of immunologic tolerance. Co-inhibitory receptors including programmed cell death-1 (PD-1) confer peripheral tolerance to prevent autoimmunity. SAP (SH2D1A) is an adaptor molecule that is important in T cell signaling and has been shown to interact with signaling lymphocytic activation molecule (SLAM) family receptors also in the context of self-tolerance. We recently reported that SAP interferes with PD-1 function. In the current study, we investigated the levels of SAP and PD-1 in patients with rheumatoid arthritis (RA) to further understand what role they play in disease activity. We observed increased SAP levels in lymphocytes of RA patients and found that PD-1 levels correlated positively with RA disease activity. Additionally, we found that SAP interacts with CD28 to inhibit T cell signaling in vitro. This work demonstrates a putative molecular mechanism for SAP mediated PD-1 inhibition.

Roles of PD-1/PD-L1 Pathway: Signaling, Cancer, and Beyond

Immunotherapies that target PD-1/PD-L1 axis have shown unprecedented success in a wide variety of human cancers. PD-1 is one of the key coinhibitory receptors expressed on T cells upon T cell activation. After engagement with its ligands, mainly PD-L1, PD-1 is activated and recruits the phosphatase SHP-2 in proximity to T cell receptor (TCR) and CD28 signaling. This event results in dephosphorylation and attenuation of key molecules in TCR and CD28 pathway, leading to inhibition of T cell proliferation, activation, cytokine production, altered metabolism and cytotoxic T lymphocytes (CTLs) killer functions, and eventual death of activated T cells. Bodies evolve coinhibitory pathways controlling T cell response magnitude and duration to limit tissue damage and maintain self-tolerance. However, tumor cells hijack these inhibitory pathways to escape host immune surveillance by overexpression of PD-L1. This provides the scientific rationale for clinical application of immune checkpoint inhibitors in oncology. The aberrantly high expression of PD-L1 in tumor microenvironment (TME) can be attributable to the "primary" activation of multiple oncogenic signaling and the "secondary" induction by inflammatory factors such as IFN-γ. Clinically, antibodies targeting PD-1/PD-L1 reinvigorate the "exhausted" T cells in TME and show remarkable objective response and durable remission with acceptable toxicity profile in large numbers of tumors such as melanoma, lymphoma, and mismatch-repair deficient tumors. Nevertheless, most patients are still refractory to anti-PD-1/PD-L1 therapy. Identifying the predictive biomarkers and design rational PD-1-based combination therapy become the priorities in cancer immunotherapy. PD-L1 expression, cytotoxic T lymphocytes infiltration, and tumor mutation burden (TMB) are generally considered as the most important factors affecting the effectiveness of PD-1/PD-L1 blockade. The revolution in cancer immunotherapy achieved by PD-1/PD-L1 blockade offers the paradigm for scientific translation from bench to bedside. The next decades will without doubt witness the renaissance of immunotherapy.

Genetic and epigenetic alteration of the programmed cell death 1 in rheumatoid arthritis

BACKGROUND

Rheumatoid arthritis (RA) is an autoimmune disease where both genetics and epigenetics are contributing factors. In order to discover genetic and epigenetic associations with RA and its phenotypes, we analysed RNA expression, DNA variations and DNA methylation of programmed cell death 1 (PDCD1) in a cohort of RA patients and healthy controls.

METHODS

RA patients (n = 206) and healthy controls (n = 234) were included for analysis of PDCD1 expression, PDCD1 polymorphisms and PDCD1 methylation. Differences in continuous variables between groups were compared by applying t tests. Associations between phenotypes and genotypes were evaluated with contingency tables. Sensitivity analyses were conducted to confirm the robustness of results, considering potential confounding factors and different treatment response definitions. Odds ratio (OR) and 95% confidence interval (95% CI) were calculated.

RESULTS

Higher expression of PDCD1 was found in RA compared to controls (P < 0.001), with similar PDCD1 polymorphisms in RA and controls. rs36084323 decreased inadequate response to conventional synthetic disease-modifying antirheumatic drugs (OR = 0.37, 95% CI = 0.19-0.72, P = 0.003), and rs41386349 increased rheumatoid factor seropositivity (OR = 11.89, 95% CI = 1.57-89.87, P = 0.003). Sensitivity analysis adjusting for further potential confounders and using different treatment response definition indicated similar results. Additionally, DNA methylation change at regulatory region of PDCD1 was detected in RA (P = 0.036).

CONCLUSION

Altogether, this was the first study to suggest genetic and epigenetic changes of PDCD1 in RA subsets and RA. Independent prospective cohorts are awaited to address the implications of these genetic and epigenetic changes in disease pathogenesis and phenotypes of RA.

PD-1 Polymorphisms Are Associated with Susceptibility of Acute Anterior Uveitis in Chinese Population

Acute anterior uveitis (AAU) is an ordinary type of uveitis, which is an autoimmune disease produced by T cells. Programmed apoptosis protein 1 (PD-1) is a vital negative regulatory protein of immune tolerance. We detect the single nucleotide polymorphisms (SNPs) rs41386349, rs10204525, and rs2227982 of PD-1 to investigate the correlation between PD-1 polymorphisms and AAU. A total of 166 AAU patients and 263 controls were recruited in this case-control study. Compared with controls, the frequencies of the GG genotypes were higher in rs10204525 in AAU patients (p = 0.012). There were obvious increases in frequencies of the TT genotypes in rs2227982 and the GG genotypes in rs10204525 in human leukocyte antigen (HLA)-B27-negative AAU patients compared with controls (p = 0.03; p = 0.015, respectively). There were also increases in frequencies of TT genotypes in rs2227982 and the GG genotypes in rs10204525 in the patients without ankylosing spondylitis (AS) when compared with controls (p = 0.021; p = 0.003, respectively). Furthermore, the frequencies of TT genotypes in rs2227982 were higher in female patients diagnosed with AAU than with control group (p = 0.033). Our results showed that SNPs rs2227982 and rs10204525 were interrelated to AAU; the influence on AAU could be related with gender, HLA-B27, and AS status.

High PD-L1 expression in the tumour cells did not correlate with poor prognosis of patients suffering for oral squamous cells carcinoma: A meta-analysis of the literature

OBJECTIVES

Oral cancer represents one of the most common malignancies in humans. Its prognosis is still poor, despite the most recent improvements in therapies. An increasing attention is placed on the role of programmed death ligand 1 (PD-L1) in the tumour immunity and its potential function as a marker for tumour prognosis. Whether PD-L1 expression is a prognostic factor for the poor outcomes in oral squamous cell carcinoma is still controversial. This study aimed to investigate, through a meta-analysis, a potential correlation between PD-L1 expression and the prognostic outcomes in patients with oral squamous cell carcinoma.

MATERIALS AND METHODS

The studies were identified by searching PubMed, SCOPUS, Web of Science and were assessed by two of the authors. After the selection process, 11 articles met eligibility criteria and were included in the meta-analysis. Quality assessment of studies was performed according to the REMARK guidelines, and the risk of biases across studies was investigated through Q and I² tests. Meta-analysis was performed to investigate the association between the PD-L1 expression either overall survival (OS), disease-free survival (DFS), disease-specific survival (DSS), gender and lymph node metastasis.

RESULTS

A total of 1060 patients were analysed in the 11 studies included in the meta-analysis. Pooled analysis revealed that the expression of PD-L1 did not correlate with poor OS (HR, 0.60; 95% CI: [0.33, 1.10]; P = 0.10), DFS (HR, 0.62; 95% CI: [0.21, 1.88]; P = 0.40), DSS (HR, 2.05; 95% CI: [0.53, 7.86]; P = 0.29 and lymph node metastasis (HR, 1.15; 95% CI: [0.74, 1.81]; P = 0.53). Furthermore, results of the meta-analysis showed that high expression of PD-L1 is two times more frequent in female patients (OR, 0.5; 95% CI: [0.36, 0.69]; P < 0.0001) compared to males. For all the three outcomes analysed, a high rate of heterogeneity was detected (I²  > 50%).

DISCUSSION

High PD-L1 expression did not correlate with poor prognosis of patients suffering for oral squamous cell carcinoma. Studies published on the topic showed a significant variation in results, limiting the use of PD-L1 expression by immunohistochemistry as prognostic biomarker in clinical practice.

Immune Checkpoints as Therapeutic Targets in Autoimmunity

Antibodies that block the immune checkpoint receptors PD1 and CTLA4 have revolutionized the treatment of melanoma and several other cancers, but in the process, a new class of drug side effect has emerged—immune related adverse events. The observation that therapeutic blockade of these inhibitory receptors is sufficient to break self-tolerance, highlights their crucial role in the physiological modulation of immune responses. Here, we discuss the rationale for targeting immune checkpoint receptors with agonistic agents in autoimmunity, to restore tolerance when it is lost. We review progress that has been made to date, using Fc-fusion proteins, monoclonal antibodies or other novel constructs to induce immunosuppressive signaling through these pathways. Finally, we explore potential mechanisms by which these receptors trigger and modulate immune cell function, and how understanding these processes might shape the design of more effective therapeutic agents in future.

PD-1 has a unique capacity to inhibit allergen-specific human CD4+ T cell responses

T lymphocytes have a crucial role in initiating and promoting type I allergies. Their responses are tightly regulated by numerous activating and inhibitory signals provided by APCs. Here we have addressed the role of the major coinhibitory receptors PD-1, CTLA-4, BTLA and LAG-3 in allergen-specific CD4⁺ T cell responses. PBMCs of healthy individuals and 41 patients allergic to house dust mites, birch, grass or mugwort pollen were stimulated with allergenic extracts and expression of coinhibitory receptors on responding CD4⁺ T cells was assessed. Blocking antibodies to PD-1, CTLA-4, BTLA and LAG-3 were used to evaluate the role of coinhibitory pathways. Allergen-specific CD4⁺ T cells showed strong upregulation of PD-1, LAG-3 and CTLA-4 upon stimulation, whereas BTLA was downregulated. Blockade of PD-1 strongly enhanced proliferation and cytokine production (IL-10; T_H1 cytokines IFN-γ, TNF-α; T_H2 cytokines IL-5, IL-13) of allergen-specific CD4⁺ T cells derived from allergic as well as non-allergic individuals. BTLA blockade enhanced proliferation but not cytokine production in response to house dust mite extract. Blocking LAG-3 was ineffective and surprisingly, we observed reduced proliferation and cytokine production in presence of a CTLA-4 antibody. Our results point to a unique potency of PD-1 pathways to dampen allergen-specific human T cells.

Inflammatory cytokines compromise programmed cell death-1 (PD-1)-mediated T cell suppression in inflammatory arthritis through up-regulation of soluble PD-1

The programmed cell death 1 (PD‐1) receptor plays a major role in regulating T cell activation. Our aim was to determine how inflammation influences PD‐1‐mediated T cell suppression. Flow cytometry analysis of rheumatoid arthritis (RA) and psoriatic arthritis (PsA) synovial fluid (SF) mononuclear cells showed an increase in the percentage of PD‐1⁺ cells within the CD4⁺ and CD8⁺ T cell compartment compared to paired peripheral blood (PB). Upon in‐vitro T cell receptor (TCR) stimulation of healthy control (HC) CD4⁺ T cells in the presence of plate‐bound PD‐L1fc chimera, significantly decreased proliferation and interferon (IFN)‐γ secretion was observed. In contrast, CD4⁺ T cells from RA and PsA PB and SF appeared resistant to such PD‐1‐mediated inhibition. Addition of the proinflammatory cytokines tumour necrosis factor (TNF)α, interleukin (IL)‐6 and IL‐1β, which were increased in RA and PsA SF compared to osteoarthritis (OA) SF, consistently abrogated PD‐1‐mediated suppression in HC CD4⁺ T cell cultures. This effect was reversed by inhibitors of these cytokines. Soluble PD‐1 (sPD‐1) levels were increased in cell culture supernatants from TNFα and IL‐6‐stimulated cultures compared to untreated controls, and also in RA and PsA, but not in OA, serum and SF. Functionally, addition of sPD‐1fc counteracted PD‐1‐mediated suppression of HC CD4⁺ T cells, and increased T cell proliferation in HC CD4⁺ T cell/monocyte co‐cultures. These in‐vitro findings indicate that CD4⁺ T cells from patients with RA and PsA show increased resistance to PD‐1‐mediated suppression, which may be explained in part by the presence of soluble PD‐1 in the inflammatory environment.

PD-1/PD-L and autoimmunity: A growing relationship

Programmed death 1 (PD-1) and its ligands, namely PD-L1 and PD-L2, are one of the key factors responsible for inhibitory T cell signaling, mediating the mechanisms of tolerance and providing immune homeostasis. Mounting evidence demonstrates that impaired PD-1:PD-L function plays an important role in a variety of autoimmune diseases such as Type 1 diabetes (T1D), encephalomyelitis, inflammatory bowel diseases (IBD), Rheumatoid Arthritis (RA), autoimmune hepatitis (AIH), Behcet's disease (BD), myasthenia gravis (MG), autoimmune uveitis (AU), Sjögren's syndrome (SjS), systemic lupus erythematosus (SLE), systemic sclerosis (SSc), myocarditis, and ankylosing spondylitis (AS). By investigating the candidate genes, genome-wide association studies, and identification of single nucleotide polymorphisms (SNPs) in PD-1 gene in humans, it has been shown that there is a higher risk in relevant genetic associations with developing autoimmune diseases in certain ethnic groups. In this review we have tried to present a comprehensive role of PD-1:PD-L in all recently studied autoimmune diseases.

Current and future biomarkers in allergic asthma

Diagnosis early in life, sensitization, asthma endotypes, monitoring of disease and treatment progression are key motivations for the exploration of biomarkers for allergic rhinitis and allergic asthma. The number of genes related to allergic rhinitis and allergic asthma increases steadily; however, prognostic genes have not yet entered clinical application. We hypothesize that the combination of multiple genes may generate biomarkers with prognostic potential. The current review attempts to group more than 161 different potential biomarkers involved in respiratory inflammation to pave the way for future classifiers. The potential biomarkers are categorized into either epithelial or infiltrate-derived or mixed origin, epithelial biomarkers. Furthermore, surface markers were grouped into cell-type-specific categories. The current literature provides multiple biomarkers for potential asthma endotypes that are related to T-cell phenotypes such as Th1, Th2, Th9, Th17, Th22 and Tregs and their lead cytokines. Eosinophilic and neutrophilic asthma endotypes are also classified by epithelium-derived CCL-26 and osteopontin, respectively. There are currently about 20 epithelium-derived biomarkers exclusively derived from epithelium, which are likely to innovate biomarker panels as they are easy to sample. This article systematically reviews and categorizes genes and collects current evidence that may promote these biomarkers to become part of allergic rhinitis or allergic asthma classifiers with high prognostic value.

Accumulation of CD5+CD19+ B lymphocytes expressing PD-1 and PD-1L in hypertrophied pharyngeal tonsils

Programmed death-1 (PD-1) is one of the most important inhibitory co-receptors expressed predominantly on activated T and B lymphocytes whose expression could be sustained by permanent antigenic stimulation accompanying chronic or recurrent tonsillitis. The expression of PD-1 and PD-1L was analyzed using flow cytometry on hypertrophied tonsils collected from 57 children. We observed high expression of PD-1 and PD-1L on certain lymphocytes subpopulations of hypertrophied tonsils; among T cells, the expression of PD-1 on protein level was higher on CD4⁺ cells (70.3 %) than on CD8⁺ cells (35 %). Interestingly, a limited expression of PD-1 was observed on CD19⁺ B lymphocytes (6.5 %), while CD5⁺CD19⁺ B cells overexpressed PD-1 (52.5 %). Moreover, the expression of PD-1L was also higher on CD5⁺CD19⁺ B cells (16.5 %) than on CD19⁺ B cells (3.5 %) and on CD4⁺ T cells (20 %) than on CD8⁺ T cells (10 %). PD-1 and PD-1L expressions correlated only on CD5⁺CD19⁺ cells. In conclusion, high expression of PD-1 and PD-1L on T and B cells could represent hallmark of immune system adaptation to chronic antigenic exposition in patients with tonsillitis.

Genetic absence of PD-1 promotes accumulation of terminally differentiated exhausted CD8+ T cells

Programmed Death-1 (PD-1) has received considerable attention as a key regulator of CD8(+) T cell exhaustion during chronic infection and cancer because blockade of this pathway partially reverses T cell dysfunction. Although the PD-1 pathway is critical in regulating established "exhausted" CD8(+) T cells (TEX cells), it is unclear whether PD-1 directly causes T cell exhaustion. We show that PD-1 is not required for the induction of exhaustion in mice with chronic lymphocytic choriomeningitis virus (LCMV) infection. In fact, some aspects of exhaustion are more severe with genetic deletion of PD-1 from the onset of infection. Increased proliferation between days 8 and 14 postinfection is associated with subsequent decreased CD8(+) T cell survival and disruption of a critical proliferative hierarchy necessary to maintain exhausted populations long term. Ultimately, the absence of PD-1 leads to the accumulation of more cytotoxic, but terminally differentiated, CD8(+) TEX cells. These results demonstrate that CD8(+) T cell exhaustion can occur in the absence of PD-1. They also highlight a novel role for PD-1 in preserving TEX cell populations from overstimulation, excessive proliferation, and terminal differentiation.

The programmed cell death 1 gene polymorphisms (PD 1.3 G/A, PD 1.5 C/T and PD 1.9 C/T) and susceptibility to ankylosing spondylitis: a meta-analysis

OBJECTIVE

The objective is to integrate all the eligible studies and investigate whether the programmed cell death 1 (PDCD-1) gene polymorphisms (PD 1.3 G/A, PD 1.5 C/T, and PD 1.9 C/T polymorphism) are correlated with ankylosing spondylitis risk (AS). Ankylosing spondylitis is a chronic inflammatory disease, and several genetic and environmental factors play an important role in the development and progression of AS. Significant associations between PDCD-1 gene polymorphisms (PD 1.3 G/A, PD 1.5 C/T or PD 1.9 C/T) and AS risk have been reported; however, some of these results are controversial.

METHODS

A systematic online search was performed using PubMed, EMBASE, Web of Science, and the Cochrane Library to identify case-control studies investigating the relationship between PD 1.3 G/A, PD 1.5 C/T, and PD 1.9 C/T polymorphisms and the susceptibility of AS. The pooled odds ratio (OR) with 95 % confidence interval (CI; 95 %) was calculated to assess the associations, and subgroup meta-analyses were performed according to the ethnicity of the study populations.

RESULTS

Five studies involving 909 cases and 982 controls met the inclusion criteria after assessment by two reviewers. Overall, there were no significant associations between PD 1.3 G/A and PD 1.5 C/T polymorphisms and AS risk. With regard to PD 1.9 C/T polymorphism, a significant association was found under the allele contrast model (T vs. C: OR 1.74, 95 % CI 1.48-2.06, P < 0.001), heterozygote model (CT vs. CC: OR 2.43, 95 % CI 1.65-3.59, P < 0.001), homozygote model (TT vs. CC: OR 1.87, 95 % CI 1.30-2.71, P = 0.001), and dominant model (CT/TT vs. CC: OR 2.29, 95 % CI 1.65-3.18, P < 0.001). In the subgroup analysis of ethnicity, no significant associations were found between PD 1.3 G/A, PD 1.5 C/T polymorphisms, and AS risk in either Asian or Caucasian populations. However, our study suggested that PD 1.9 C/T polymorphism was significantly associated with AS in Asian populations (T vs. C: OR 1.72, 95 % CI 1.46-2.04, P < 0.001; CT vs. CC: OR 2.44, 95 % CI 1.56-3.82, P < 0.001; TT vs. CC: OR 1.88, 95 % CI 1.30-2.73, P = 0.001; and CT/TT vs. CC: OR 2.29, 95 % CI 1.58-3.32, P < 0.001) but not in Caucasian populations.

CONCLUSION

The PD 1.9 C/T polymorphism may be involved in susceptibility to AS, particular in Asian populations; however, no significant associations were found between PD 1.3 G/A, PD 1.5 C/T polymorphisms, and AS risk in either Asians or Caucasians.

Association between a PD-1 gene polymorphism and antisperm antibody-related infertility in Iranian men

OBJECTIVE

Programmed cell death-1 (PD-1, Pdcd1), an immunoreceptor belonging to the CD28/CTLA-4 family negatively regulates antigen receptor signalling by recruiting protein tyrosine phosphatase, SHP-2 upon interacting with either of two ligands, PD-L1 or PD-L2. This study investigates PD-1 gene polymorphism in patients with antisperm antibody-related infertility

METHODS

Genotyping was performed by polymerase chain reaction and restriction enzyme digestion (PCR-RFLP), this polymorphism was genotyped in 145 Iranian subjects (61 patients with antisperm antibody-related infertility and 84 healthy controls).

RESULTS

Patients frequencies of the G/A genotype in comparison with healthy controls (38.2 % vs. 32.7 %, OR =1.21, P = 0.35) were not significantly different. However, G/G and A/A genotype frequencies between patients and healthy controls were significantly different (P = 0.042, P = 0.00001, respectively). Also, allele frequencies of this polymorphism were significantly different (P = 0.0012) in patients compared to healthy controls.

CONCLUSION

According to these results, there is a correlation between PD-1 gene polymorphism and susceptibility to antisperm antibody-related infertility in our study group.

A rheostat for immune responses: the unique properties of PD-1 and their advantages for clinical application

PD-1, a negative coreceptor expressed on antigen-stimulated T cells and B cells, seems to serve as a 'rheostat' of the immune response. The molecular mechanisms of the functions of PD-1, in conjunction with the mild, chronic and strain-specific autoimmune phenotypes of PD-1-deficient mice, in contrast to the devastating fatal autoimmune disease of mice deficient in the immunomodulatory receptor CTLA-4, suggest that immunoregulation by PD-1 is rather antigen specific and is mainly cell intrinsic. Such unique properties make PD-1 a powerful target for immunological therapy, with highly effective clinical applications for cancer treatment.

An exon polymorphism of programmed cell death 1 gene is associated with both the susceptibility and thoracolumbar kyphosis severity of ankylosing spondylitis in a Chinese Han population

BACKGROUND

Although human leukocyte antigen (HLA)-B27 gene is the major susceptible gene associated with ankylosing spondylitis (AS), it has been recognized that non-HLA-B27 genes also play key roles in the development of AS. The purpose of this study is to investigate whether a single nucleotide polymorphism (SNP) in the exon region of the programmed cell death 1 (PDCD-1) gene is associated with the susceptibility or the thoracolumbar kyphosis severity of AS in a Chinese Han population.

METHODS

A total of 255 AS patients between January 2008 and October 2012 were recruited in this study. Two hundred and three healthy patients were recruited as normal controls. According to the severity of thoracolumbar kyphosis, the AS patients were further divided into group A (patients with kyphosis <70°, n = 135) and group B (patients with kyphosis ≥70°, n = 120). One exon polymorphism, rs2227982 (C/T) of PDCD-1 gene, was selected for analysis. Genotyping was performed by TaqMan probe assays in all the subjects.

RESULTS

There were significant differences of genotype distributions of rs2227982 between AS patients and normal controls. The frequency of the T allele was significantly higher in AS patients when compared with normal controls. The frequency of the T allele in group B was significantly higher than that in group A. Carriage of the TT genotype increased the risk of severe thoracolumbar kyphosis 1.9-fold in AS patients.

CONCLUSIONS

Our study confirms a significant association between the SNP rs2227982 of PDCD-1 gene and the susceptibility of AS in a Chinese Han population. Moreover, the TT genotype is suggested to be associated with the severity of thoracolumbar kyphosis secondary to AS.

Recent insights into the role of the PD-1/PD-L1 pathway in immunological tolerance and autoimmunity

Autoimmune diseases represent a heterogeneous group of conditions whose incidence is increasing worldwide. This has stimulated studies on their etiopathogenesis, derived from a complex interaction between genetic and environmental factors, in order to improve prevention and treatment of these disorders. The relevance of T regulatory cells and of the PD-1/PD-L1 pathway in controlling immune responses has been highlighted. Recent studies have in particular elucidated the putative role of the PD-1/PD-L1 pathway in regulating T cell responses and its effects on immunological tolerance and immune-mediated tissue damage. The role of the PD-1/PD-L1 pathway in autoimmunity has been already investigated in vivo in several experimental animal models including insulin-dependent diabetes mellitus, systemic lupus erythematosus, myocarditis, encephalomyelitis, rheumatoid arthritis and inflammatory bowel diseases. With the advent of candidate gene and genome-wide association studies, single nucleotide polymorphisms (SNPs) in PD-1 gene in humans have demonstrated relevant associations with a higher risk of developing autoimmune diseases in certain ethnic groups. In this review we present recent insights into the role of the PD-1/PD-L1 pathway in regulating lymphocyte activation, promotion of T regulatory cell development and function, breakdown of tolerance and development of autoimmunity. We finally speculate on the possible development of novel therapeutic treatments in human autoimmunity by modulating the PD-1/PD-L1 pathway.

Structure and interactions of the human programmed cell death 1 receptor

PD-1, a receptor expressed by T cells, B cells, and monocytes, is a potent regulator of immune responses and a promising therapeutic target. The structure and interactions of human PD-1 are, however, incompletely characterized. We present the solution nuclear magnetic resonance (NMR)-based structure of the human PD-1 extracellular region and detailed analyses of its interactions with its ligands, PD-L1 and PD-L2. PD-1 has typical immunoglobulin superfamily topology but differs at the edge of the GFCC′ sheet, which is flexible and completely lacks a C″ strand. Changes in PD-1 backbone NMR signals induced by ligand binding suggest that, whereas binding is centered on the GFCC′ sheet, PD-1 is engaged by its two ligands differently and in ways incompletely explained by crystal structures of mouse PD-1·ligand complexes. The affinities of these interactions and that of PD-L1 with the costimulatory protein B7-1, measured using surface plasmon resonance, are significantly weaker than expected. The 3–4-fold greater affinity of PD-L2 versus PD-L1 for human PD-1 is principally due to the 3-fold smaller dissociation rate for PD-L2 binding. Isothermal titration calorimetry revealed that the PD-1/PD-L1 interaction is entropically driven, whereas PD-1/PD-L2 binding has a large enthalpic component. Mathematical simulations based on the biophysical data and quantitative expression data suggest an unexpectedly limited contribution of PD-L2 to PD-1 ligation during interactions of activated T cells with antigen-presenting cells. These findings provide a rigorous structural and biophysical framework for interpreting the important functions of PD-1 and reveal that potent inhibitory signaling can be initiated by weakly interacting receptors.

Polymorphisms in programmed death-1 gene are not associated with chronic HBV infection in Chinese patients

AIM

To investigate the association between the programmed death-1(PD-1) polymorphisms and genetic susceptibility of chronic hepatitis B virus (HBV) infection in Chinese patients.

METHODS

Two single nucleotide polymorphisms (SNPs), PD-1.1 G > A and PD-1.2 G > A, were genotyped in 539 patients with chronic HBV infection and 353 other family members (HbsAg-) from 256 nuclear families using polymerase chain reactiorestriction fragment length polymorphisms assay. The associations between PD-1 polymorphisms and genetic susceptibility of chronic HBV infection were analyzed usng the family-based association analysis method.

RESULTS

No association or linkage was detected among 539 patients. Univariate (single-marker) family-based association tests demonstrated that PD-1 genotypes, alleles and transmitted haplotypes are not associated with chronic HBV infection (all with P value more than 0.05). Transmission/disequilibrium test and sibship disequilibrium test analysis showed no excess of the alleles from heterozygous parents to affected offspring (P = 0.688880, P = 1.000000 respectively).

CONCLUSION

The data demonstrated that PD-1.1 and PD-1.2 polymorphisms are not associated with chronic HBV infection in Chinese patients.

Clinical and laboratory characteristics of Finnish lupus erythematosus patients with cutaneous manifestations

Our objective was to characterize clinical features, laboratory findings, concomitant autoimmune diseases, and smoking habits of lupus erythematosus subgroups in genetically homogeneous patients from two Dermatology Departments of Finnish University hospitals. One hundred and seventy eight discoid lupus erythematosus, 55 subacute cutaneous lupus erythematosus, and 77 systemic lupus erythematosus patients were enrolled using patients' charts from institutional database (1995-2006) and during routine control visits. Clustering analysis was performed to reveal natural groupings. Smoking at the onset of disease was significantly more common in all subgroups (57% for discoid lupus erythematosus, 35% for subacute cutaneous lupus erythematosus, and 34% for systemic lupus erythematosus) compared with the age/gender-matched prevalence in the Finnish population, suggesting smoking to be a trigger factor for cutaneous lupus. Leukopenia (38%) and lymphopenia (52%) were observed more often in patients with systemic lupus erythematosus than reported previously. Photosensitivity characterized all groups, especially patients with subacute cutaneous lupus erythematosus (87%). Of the autoimmune diseases, Sjögren's syndrome was the most common (22% of patients with systemic lupus erythematosus), followed by autoimmune thyroid disease (13% of patients with subacute cutaneous lupus erythematosus). The clustering analysis showed environmental factors (smoking) to be more involved in disease development in discoid lupus erythematosus, whereas immunological factors were more significant in initiating systemic lupus erythematosus. The high prevalence of autoimmune thyroid disease, together with photosensitivity, and the clustering profiles suggest that lupus erythematosus subtypes, especially discoid lupus erythematosus, are heterogeneic in their pathomechanisms.

Tag SNP screening of the PDCD1 gene for association with Graves' disease

OBJECTIVE

The Programmed Cell Death 1 gene (PDCD1) on chromosome 2q37.3 encodes PD-1 which is involved in providing a negative signal to activated T cells. Large case-control studies have shown association of PDCD1 with several autoimmune diseases although, to date, no such studies have been performed for Graves' disease (GD). The objective of our study was to investigate eight tag SNPs representing the majority of common variation in PDCD1 within a well-characterized large UK Caucasian GD dataset.

DESIGN

A case control association study of eight polymorphisms.

PATIENTS

2671 Graves' disease patients and 864 controls.

MEASUREMENTS

Tests for association with disease.

RESULTS

No association with disease was seen for any of the +4163, +5049, +5318, +5640, +5678 and +7078 SNPs genotyped in this study. Association was detected between the +2375 SNP (P = 0.021, OR = 1.14 [95% CI = 1.01-1.29]) and GD and a small protective effect was seen with the +6799 SNP genotypes (P = 0.028, OR = 0.77 [95% CI = 0.58-1.03]).

CONCLUSIONS

This study has, for the first time, shown that small effects within PDCD1 may contribute towards the development of GD, supporting the hypothesis that much of the currently unknown genetic contribution to GD could be due to several small genetic effects with ORs 1.2. Replication of this result is now needed to confirm our findings and justify more detailed fine mapping of a primary aetiological variant in this gene region.

The function of programmed cell death 1 and its ligands in regulating autoimmunity and infection

The programmed cell death 1 (PD-1) surface receptor binds to two ligands, PD-L1 and PD-L2. Studies have shown that PD-1-PD-L interactions control the induction and maintenance of peripheral T cell tolerance and indicate a previously unknown function for PD-L1 on nonhematopoietic cells in protecting tissues from autoimmune attack. PD-1 and its ligands have also been exploited by a variety of microorganisms to attenuate antimicrobial immunity and facilitate chronic infection. Here we examine the functions of PD-1 and its ligands in regulating antimicrobial and self-reactive T cell responses and discuss the therapeutic potential of manipulating this pathway.

Bias in association studies of systemic lupus erythematosus susceptibility due to geographical variation in the frequency of a programmed cell death 1 polymorphism across Europe

We obtained eight collections of DNA samples from ethnically matched systemic lupus erythematosus (SLE) patients and controls from five European countries totaling 783 patients and 1210 controls. A highly significant cline in the frequency of the PD1.3 A allele was found among controls but not among SLE patients. The frequency of the PD1.3 A allele increased from the Northeast to the Southwest of Europe. The cline was clearly apparent (P=1.2 x 10(-6)) when data from controls of other five SLE susceptibility studies were included in the analysis. This variation has severely biased SLE association studies owing to the lack of parallel changes in SLE patients. As a consequence, the PD1.3 A allele was more common in SLE patients than in controls in the Northeast and Center of Europe, similar to controls in Southeast Europe, and less frequent than in the controls in the Southwest of the Continent. This dissociation in allele frequencies between SLE patients and controls in different subpopulations indicated that programmed cell death 1 variation and disease susceptibility are not independent but the type of relationship is currently unclear. As allele frequency clines are common in other polymorphisms their impact in genetic epidemiology studies should be carefully considered.

Decreased Risk for Myocardial Infarction and Lower Tumor Necrosis Factor–α Levels in Carriers of Variants of the PDCD1 Gene

Increasing interest has been directed toward the inflammatory mechanisms involved in the pathogenesis of myocardial infarction (MI). In the search for genetic mechanisms underlying these inflammatory components, we studied variants of programmed cell death-1 (PDCD1), an immunoinhibitory receptor that inhibits lymphocyte activation and cytokine production, previously shown to be associated with several autoimmune disorders. The PD1.1, PD1.3, and PD1.6 polymorphisms of the PDCD1 gene were typed in the Stockholm Heart Epidemiology Program, a population-based clinical material consisting of 1179 first-time MI case patients and 1528 unaffected control subjects. Individual alleles and haplotypes were studied for association with levels of the inflammatory cytokines tumor necrosis factor-alpha (TNF-alpha), interleukin-6, and C-reactive protein and risk for MI. We observed a weak protective effect of PD1.3A allele for MI (odds ratio: 0.78, 95% confidence interval: 0.61-0.98). We also observed decreased levels of TNF-alpha in carriers of the PD1.1A/PD1.3G/PD1.6A haplotype, which is consistent with our previous observation that this haplotype may be protective from autoimmune conditions. Carriers of variants of the PDCD1 gene exhibit a decreased risk for nonfatal myocardial infarction, and PDCD1 mediates variation in TNF-alpha levels.

Genetic progress towards the molecular basis of autoimmunity

The past few years have seen the identification of PTPN22 and the confirmation of CTLA-4 as common autoimmune disease genes. Together with MHC and INS, these developments have increased the collection of confirmed susceptibility loci for autoimmunity. In this article, the latest developments related to these genes and to other recently studied candidate autoimmune susceptibility loci (PDCD1, FCRL3, SUMO4, CD25, PADI4 and SLC22A4) are reviewed. Collectively, these genes strongly indicate that aberrant inhibition of the signalling cascade initiated by activation of the T-cell receptor is involved in the aetiology of autoimmune disease. However, much basic genetic, molecular and clinical research is still needed to help us fully understand the underlying mechanisms of autoimmunity and how these translate into prognosis or therapy.