Exploring the Role of PD-1 in the Autoimmune Response: Insights into Its Implication in Systemic Lupus Erythematosus

Despite advances in understanding systemic lupus erythematosus (SLE), many challenges remain in unraveling the precise mechanisms behind the disease's development and progression. Recent evidence has questioned the role of programmed cell death protein 1 (PD-1) in suppressing autoreactive CD4+ T cells during autoimmune responses. Research has investigated the potential impacts of PD-1 on various CD4+ T-cell subpopulations, including T follicular helper (Tfh) cells, circulating Tfh (cTfh) cells, and T peripheral helper (Tph) cells, all of which exhibit substantial PD-1 expression and are closely related to several autoimmune disorders, including SLE. This review highlights the complex role of PD-1 in autoimmunity and emphasizes the imperative for further research to elucidate its functions during autoreactive T-cell responses. Additionally, we address the potential of PD-1 and its ligands as possible therapeutic targets in SLE.

Upregulation of PD-1 and its ligands and expansion of T peripheral helper cells in the nephritic kidneys of lupus-prone BXSB-Yaa mice

OBJECTIVE

This study aimed to investigate the role of the programmed cell death protein 1 (PD-1) pathway and T peripheral helper (Tph) cells in the pathogenesis of lupus nephritis using lupus-prone BXSB-Yaa mice.

METHODS

Male BXSB-Yaa mice and age-matched male C57BL/6 mice were used. The expression of PD-1 and its ligands (programmed cell death 1 ligand-1, PD-L1 and programmed cell death 1 ligand-2, PD-L2) and the phenotypes of kidney-derived cells and splenocytes expressing these molecules were analyzed by immunofluorescence and flow cytometry.

RESULTS

Nephritis spontaneously developed in 16-week-old but not in 8-week-old BXSB-Yaa or C57BL/6 mice. PD-1 was expressed on CD4+ mononuclear cells (MNCs) that infiltrated the glomeruli of 16-week-old BXSB-Yaa mice. The frequency of CD4+PD-1+CXCR5-ICOS+ kidney-derived Tph cells was higher in 16-week-old than in 8-week-old BXSB-Yaa and C57BL/6 mice, whereas the frequency of CD4+PD-1+CXCR5+ICOS+ kidney-derived T follicular helper (Tfh) cells was not significantly different between the mice. PD-L1 was constitutively expressed in the renal tubules. PD-L2 was expressed in the glomeruli of 16-week-old BXSB-Yaa mice. The frequency of PD-L1highCD11c+CD3-CD19- and PD-L2+CD11c+CD3-CD19- kidney-derived MNCs in 16-week-old BXSB-Yaa mice was significantly higher than that of the control mice. The percentage of kidney-derived Tph cells but not Tfh cells was correlated with the urinary protein levels in the nephritic mice.

CONCLUSION

The results of this study suggest that kidney-infiltrating PD-1+ Tph cells expanded concomitantly with the upregulation of PD-L1 and PD-L2 in the kidneys and the progression of lupus nephritis.

Interferon and B-cell Signatures Inform Precision Medicine in Lupus Nephritis

Introduction

Current therapeutic management of lupus nephritis (LN) fails to induce long-term remission in over 50% of patients, highlighting the urgent need for additional options.

Methods

We analyzed differentially expressed genes (DEGs) in peripheral blood from patients with active LN (n = 41) and active nonrenal lupus (n = 62) versus healthy controls (HCs) (n = 497) from the European PRECISESADS project (NTC02890121), and dysregulated gene modules in a discovery (n = 26) and a replication (n = 15) set of active LN cases.

Results

Replicated gene modules qualified for correlation analyses with serologic markers, and regulatory network and druggability analysis. Unsupervised coexpression network analysis revealed 20 dysregulated gene modules and stratified the active LN population into 3 distinct subgroups. These subgroups were characterized by low, intermediate, and high interferon (IFN) signatures, with differential dysregulation of the "B cell" and "plasma cells/Ig" modules. Drugs annotated to the IFN network included CC-motif chemokine receptor 1 (CCR1) inhibitors, programmed death-ligand 1 (PD-L1) inhibitors, and irinotecan; whereas the anti-CD38 daratumumab and proteasome inhibitor bortezomib showed potential for counteracting the "plasma cells/Ig" signature. In silico analysis demonstrated the low-IFN subgroup to benefit from calcineurin inhibition and the intermediate-IFN subgroup from B-cell targeted therapies. High-IFN patients exhibited greater anticipated response to anifrolumab whereas daratumumab appeared beneficial to the intermediate-IFN and high-IFN subgroups.

Conclusion

IFN upregulation and B and plasma cell gene dysregulation patterns revealed 3 subgroups of LN, which may not necessarily represent distinct disease phenotypes but rather phases of the inflammatory processes during a renal flare, providing a conceptual framework for precision medicine in LN.

The effect of combining PD-1 agonist and low-dose Interleukin-2 on treating systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is a chronic autoimmune disease involving multiple organs. It is often called "immortal cancer" due to the difficulties in disease treatment. As the cornerstone of immune regulation, the programmed cell death protein 1 (PD-1) has been extensively studied in the context of chronic inflammation due to its ability of regulating immune response and immunosuppression. Recently, more and more studies on rheumatic immune related complications have also focused on PD-1 and proposed that the use of PD-1 agonist could inhibit the activation of lymphocytes and alleviate SLE disease activity. In this review, we summarized the role of PD-1 in SLE, implicating its potential application as a biomarker to predict SLE disease activity; we also proposed that the combination of PD-1 agonist and low-dose IL-2 may have better therapeutic efficacy, shining light on a new direction for developing specific treatment approaches.

Expression and Significance of Programmed Death-1 and Its Ligands in the Accelerated Formation of Atherosclerosis in an Induced Murine Lupus Model

Atherosclerosis (AS) is a chronic inflammatory disease that occurs in artery walls, which seriously affects the survival and prognosis of patients with systemic lupus erythematosus (SLE). Immune and inflammatory responses have notable effects on all stages of AS. In this study, we modeled SLE combined with AS in vivo via intraperitoneal injection of pristane (2,6,10,14-tetramethylpentadecane) into apolipoprotein E-knockout (ApoE-/- ) mice that had accelerated atherosclerotic lesions compared with wild-type (WT) ApoE-/- mice. In pristane-induced ApoE-/- mice, expression of programmed death-1 (PD-1) and programmed death-ligand 1 (PD-L1) in peripheral blood and on the surfaces of atherosclerotic lesions significantly increased, and levels of proinflammatory cytokines, namely, interferon-gamma (IFN-γ) and tumor necrosis factor alpha (TNF-α) in peripheral blood were elevated. We did not detect expression of programmed death-ligand 2 (PD-L2) in the arterial plaques of either pristane-induced or WT ApoE-/- mice, nor did we observe any significant difference in PD-L2 expression in peripheral blood between the two groups. Taken together, these results suggested that PD-1/PD-L1 signaling pathway might play an important regulatory role in the progression of AS in an induced murine lupus model which implies a potential target for treatment of AS in SLE.

Insights Into the Host Contribution of Endocrine Associated Immune-Related Adverse Events to Immune Checkpoint Inhibition Therapy

Blockade of immune checkpoints transformed the paradigm of systemic cancer therapy, enabling substitution of a cytotoxic chemotherapy backbone to one of immunostimulation in many settings. Invigorating host immune cells against tumor neo-antigens, however, can induce severe autoimmune toxicity which in many cases requires ongoing management. Many immune-related adverse events (irAEs) are clinically and pathologically indistinguishable from inborn errors of immunity arising from genetic polymorphisms of immune checkpoint genes, suggesting a possible shared driver for both conditions. Many endocrine irAEs, for example, have analogous primary genetic conditions with varied penetrance and severity despite consistent genetic change. This is akin to onset of irAEs in response to immune checkpoint inhibitors (ICIs), which vary in timing, severity and nature despite a consistent drug target. Host contribution to ICI response and irAEs, particularly those of endocrine origin, such as thyroiditis, hypophysitis, adrenalitis and diabetes mellitus, remains poorly defined. Improved understanding of host factors contributing to ICI outcomes is essential for tailoring care to an individual’s unique genetic predisposition to response and toxicity, and are discussed in detail in this review.

Immune checkpoints and the multiple faces of B cells in systemic lupus erythematosus

PURPOSE OF REVIEW

B-lymphocytes are crucial in the pathogenesis of systemic lupus erythematosus (SLE), including autoantibody production, antigen presentation, co-stimulation, and cytokine secretion. Co-stimulatory and co-inhibitory molecules control interactions between B and T cells during an inflammatory response, which is essential for an appropriate host protection and maintenance of self-tolerance. Here, we review recent findings about checkpoint molecules and SLE B cells including their potential therapeutic implications and experiences from clinical trials.

RECENT FINDINGS

Most prominent checkpoint molecules involved in pathologic B and T cell interaction in SLE are CD40/CD40L and inducible co-stimulator/ICOSL, both also intimately involved in the formation of germinal centers and ectopic lymphoid tissue. Dysregulations of inhibitory checkpoint molecules, like programmed death-1/programmed death-ligand 1 and B- and T-lymphocyte attenuator have been suggested to impair B cell functions in SLE recently.

SUMMARY

Accumulating evidence indicates that dampening immune responses by either blocking co-activating signals or enhancing co-inhibitory signals in different cell types is a promising approach to treat autoimmune diseases to better control active disease but may also allow resolution of chronic autoimmunity.

Cellular and molecular regulation of the programmed death-1/programmed death ligand system and its role in multiple sclerosis and other autoimmune diseases

Programmed Cell Death 1 (PD-1) receptor and its ligands (PD-Ls) are essential to maintain peripheral immune tolerance and to avoid tissue damage. Consequently, altered gene or protein expression of this system of co-inhibitory molecules has been involved in the development of cancer and autoimmunity. Substantial progress has been achieved in the study of the PD-1/PD-Ls system in terms of regulatory mechanisms and therapy. However, the role of the PD-1/PD-Ls pathway in neuroinflammation has been less explored despite being a potential target of treatment for neurodegenerative diseases. Multiple Sclerosis (MS) is the most prevalent, chronic, inflammatory, and autoimmune disease of the central nervous system that leads to demyelination and axonal damage in young adults. Recent studies have highlighted the key role of the PD-1/PD-Ls pathway in inducing a neuroprotective response and restraining T cell activation and neurodegeneration in MS. In this review, we outline the molecular and cellular mechanisms regulating gene expression, protein synthesis and traffic of PD-1/PD-Ls as well as relevant processes that control PD-1/PD-Ls engagement in the immunological synapse between antigen-presenting cells and T cells. Also, we highlight the most recent findings regarding the role of the PD-1/PD-Ls pathway in MS and its murine model, experimental autoimmune encephalomyelitis (EAE), including the contribution of PD-1 expressing follicular helper T (TFH) cells in the pathogenesis of these diseases. In addition, we compare and contrast results found in MS and EAE with evidence reported in other autoimmune diseases and their experimental models, and review PD-1/PD-Ls-targeting therapeutic approaches.

Significance of PD1 Alternative Splicing in Celiac Disease as a Novel Source for Diagnostic and Therapeutic Target

Background

We have focused on the alteration of the PD-1/PD-L1 pathway in celiac disease and discussed the roles of the PD1 pathway in regulating the immune response. We explored the idea that the altered mRNA splicing process in key regulatory proteins could represent a novel source to identify diagnostic, prognostic, and therapeutic targets in celiac disease.

Methods

We characterized the PD1 mRNA variants' profile in CD patients and in response to gluten peptides' incubation after in vitro experiments. Total RNA from whole blood was isolated, and the coding region of the human PD-1 mRNA was amplified by cDNA PCR.

Results

PCR amplification of the human PD-1 coding sequence revealed an association between the over-expression of the sPD-1 protein and the PD-1Δex3 transcript in celiac disease. Thus, we have found three novel alternative spliced isoforms, two of which result in a truncated protein and the other isoform with a loss of 14 aa of exon 2 and complete exon 3 (Δ3) which could encode a new soluble form of PD1 (sPD-1).

Conclusions

Our study provides evidence that dietary gluten can modulate processes required for cell homeostasis through the splicing of pre-mRNAs encoding key regulatory proteins, which represents an adaptive mechanism in response to different nutritional conditions.

PDCD1 Polymorphisms May Predict Response to Anti-PD-1 Blockade in Patients With Metastatic Melanoma

A significant number of patients (pts) with metastatic melanoma do not respond to anti-programmed cell death 1 (PD1) therapies. Identifying predictive biomarkers therefore remains an urgent need. We retrospectively analyzed plasma DNA of pts with advanced melanoma treated with PD-1 antibodies, nivolumab or pembrolizumab, for five PD-1 genotype single nucleotide polymorphisms (SNPs): PD1.1 (rs36084323, G>A), PD1.3 (rs11568821, G>A), PD1.5 (rs2227981, C>T) PD1.6 (rs10204225, G>A) and PD1.9 (rs2227982, C>T). Clinico-pathological and treatment parameters were collected, and presence of SNPs correlated with response, progression free survival (PFS) and overall survival (OS). 115 patients were identified with a median follow up of 18.7 months (range 0.26 – 52.0 months). All were Caucasian; 27% BRAF V600 mutation positive. At PD-1 antibody commencement, 36% were treatment-naïve and 52% had prior ipilimumab. The overall response rate was 43%, 19% achieving a complete response. Overall median PFS was 11.0 months (95% CI 5.4 - 17.3) and median OS was 31.1 months (95% CI 23.2 - NA). Patients with the G/G genotype had more complete responses than with A/G genotype (16.5% vs. 2.6% respectively) and the G allele of PD1.3 rs11568821 was significantly associated with a longer median PFS than the AG allele, 14.1 vs. 7.0 months compared to the A allele (p=0.04; 95% CI 0.14 – 0.94). No significant association between the remaining SNPs and responses, PFS or OS were observed. Despite limitations in sample size, this is the first study to demonstrate an association of a germline PD-1 polymorphism and PFS in response to anti-PD-1 therapy in pts with metastatic melanoma. Extrinsic factors like host germline polymorphisms should be considered with tumor intrinsic factors as predictive biomarkers for immune checkpoint regulators.

Association between PDCD1 gene polymorphisms and psoriasis susceptibility in the Chinese population

BACKGROUND

As an immune regulator expressed on the surface of activated T cells, programmed cell death 1 (PDCD1) plays an important role in psoriasis. However, whether PDCD1 genetic polymorphism is associated with psoriasis has yet to be explored.

OBJECTIVE

To study the association between polymorphisms of the immune-related gene PDCD1 and psoriasis susceptibility in the Chinese population, to illustrate the genetic mechanism of psoriasis and provide new research ideas for the diagnosis and treatment of psoriasis (PS).

METHODS

Overall, 128 psoriasis patients and 88 healthy controls were included in this study. Using polymerase chain reaction (PCR)-Sanger sequencing analysis, six PDCD1 single nucleotide polymorphisms (SNPs) were sequenced: PD1.1, PD1.3, PD1.4, PD1.5, PD1.6, and PD1.9.

RESULTS

Among the six tested SNPs, PD1.6 showed a significant association with psoriasis in genotype and allele frequency distribution. The G allele of PD1.6 increased the risk of psoriasis (P = 0.03). In contrast, the other five SNPs failed to show association with psoriasis. Further analysis within the patient group showed that the frequency of the PD1.6 G allele was relatively high in severe psoriasis, but the difference was nonsignificant.

CONCLUSION

PDCD1 gene polymorphism is associated with psoriasis. The population carrying PD1.6 allele G are at a higher risk of developing psoriasis, though the severity of psoriasis does not correlate with PD1.6 polymorphism.

PDCD1 and IFNL4 genetic variants and risk of developing hepatitis C virus-related diseases

BACKGROUND

Genetic variants of IFNL4 and PDCD1 genes have been shown to influence the spontaneous clearance of hepatitis C virus (HCV) infection. We investigated the IFNL4 rs12979860 and the PDCD1 polymorphisms in 734 HCV-positive patients, including 461 cases with liver disease of varying severity and 273 patients with lymphoproliferative disorders to determine the association of these genes with patient's outcome.

METHODS

Expression levels of PDCD1 mRNA encoded by haplotypes were investigated by quantitative PCR in hepatocellular carcinoma (HCC) tissue and peripheral blood mononuclear cells. Flow cytometry was used to detect PD-1 and its ligand PD-L1.

RESULTS

The frequency of IFNL4 rs12979860 C/T or T/T genotypes was significantly higher in patients with HCV-related diseases than blood donors (P < .0001). Patients expressing the IFNλ4 variant with one amino acid change that reduces IFNλ4 secretion was found increased in frequency in HCV-related diseases compared to HCC PDCD1 mRNA levels in HCC tissue were significantly higher in cases carrying the PD-1.3 A or the PD-1.7 G allele (P = .0025 and P = .0167). Linkage disequilibrium (LD) between PD-1.3 and IFNL4 was found in patients with mixed cryoglobulinaemia (MC) only (LD = 0 in HCC; LD = 72 in MC). PBMCs of MC patients expressed low levels of PD-L1 in CD19+IgM+B cells and of PD-1 in CD4+T cells suggesting the involvement of regulatory B cell-T cell interaction to the pathogenesis of MC.

CONCLUSION

Collectively, our data indicate an important contribution of IFNλ4 expression to the development of HCV-related HCC and an epistatic contribution of IFNL4 and PDCD1 in MC.

LAY SUMMARY

Studies of IFNL4 and PDCD1 genes are helpful to better understand the role of host genetic factors and immune antigens influencing the outcome of HCV-related diseases. Our data support an association between the expression of IFNλ4, which prevents the expression of IFNλ3, with all the different HCV-related diseases studied, and besides, evidence that a higher IFNλ4 expression is associated with hepatocellular at a younger age. The expression pattern of low PD-L1 on B cells and high PD-1 on CD4+T-cells in patients with HCV-positive cryoglobulinaemia suggests a critical role of the PD-1/PD-L1 signaling in modulating B cell-T cell interaction in this lymphoproliferative disease.

Novel human immunomodulatory T cell receptors and their double-edged potential in autoimmunity, cardiovascular disease and cancer

In the last decade, approaches based on T cells and their immunomodulatory receptors have emerged as a solid improvement in treatments for various types of cancer. However, the roles of these molecules in the therapeutic context of autoimmune and cardiovascular diseases are still relatively unexplored. Here, we review the best known and most commonly used immunomodulatory T cell receptors in clinical practice (PD-1 and CTLA-4), along with the rest of the receptors with known functions in animal models, which have great potential as modulators in human pathologies in the medium term. Among these other receptors is the receptor CD69, which has recently been described to be expressed in mouse and human T cells in autoimmune and cardiovascular diseases and cancer. However, inhibition of these receptors individually or in combination by drugs or monoclonal antibodies generates a loss of immunological tolerance and can trigger multiple autoimmune disorders in different organs and immune-related adverse effects. In the coming decades, knowledge on the functions of different immunomodulatory receptors will be pivotal for the development of new and better therapies with less harmful side effects. In this review, we discuss the roles of these receptors in the control of immunity from a perspective focused on therapeutic potential in not only cancer but also autoimmune diseases, such as systemic lupus erythematosus, autoimmune diabetes and rheumatoid arthritis, and cardiovascular diseases, such as atherosclerosis, acute myocardial infarction, and myocarditis.

PD-1H (VISTA)-mediated suppression of autoimmunity in systemic and cutaneous lupus erythematosus

Systemic lupus erythematosus (SLE) and discoid lupus erythematosus (DLE) of the skin are autoimmune diseases characterized by inappropriate immune responses against self-proteins; the key elements that determine disease pathogenesis and progression are largely unknown. Here, we show that mice lacking immune inhibitory receptor VISTA or programmed death-1 homolog (PD-1H KO) on a BALB/c background spontaneously develop cutaneous and systemic autoimmune diseases resembling human lupus. Cutaneous lupus lesions of PD-1H KO mice have clustering of plasmacytoid dendritic cells (pDCs) similar to human DLE. Using mass cytometry, we identified proinflammatory neutrophils as critical early immune infiltrating cells within cutaneous lupus lesions of PD-1H KO mice. We also found that PD-1H is highly expressed on immune cells in human SLE, DLE lesions, and cutaneous lesions of MRL/lpr mice. A PD-1H agonistic monoclonal antibody in MRL/lpr mice reduces cutaneous disease, autoantibodies, inflammatory cytokines, chemokines, and immune cell expansion. Furthermore, PD-1H on both T cells and myeloid cells including neutrophils and pDCs could transmit inhibitory signals, resulting in reduced activation and function, establishing PD-1H as an inhibitory receptor on T cells and myeloid cells. On the basis of these findings, we propose that PD-1H is a critical element in the pathogenesis and progression of lupus, and PD-1H activation could be effective for treatment of systemic and cutaneous lupus.

Systemic Sclerosis Perturbs the Architecture of the Immunome

Systemic sclerosis (SSc) is an autoimmune disease characterized by excessive fibrosis of skin and internal organs, and vascular dysfunction. Association of T and B cell subsets has been reported in SSc; however, there is lack of systematic studies of functional relations between immune cell subsets in this disease. This lack of mechanistic knowledge hampers targeted intervention. In the current study we sought to determine differential immune cell composition and their interactions in peripheral blood of SSc patients. Mononuclear cells from blood of SSc patients (n = 20) and healthy controls (n = 10) were analyzed by mass cytometry using a 36-marker (cell surface and intracellular) panel. Transcriptome analysis (m-RNA sequencing) was performed on sorted T and B cell subsets. Unsupervised clustering analysis revealed significant differences in the frequencies of T and B cell subsets in patients. Correlation network analysis highlighted an overall dysregulated immune architecture coupled with domination of inflammatory senescent T cell modules in SSc patients. Transcriptome analysis of sorted immune cells revealed an activated phenotype of CD4 and mucosal associated invariant T (MAIT) cells in patients, accompanied by increased expression of inhibitory molecules, reminiscent of phenotype exhibited by functionally adapted, exhausted T cells in response to chronic stimulation. Overall, this study provides an in-depth analysis of the systemic immunome in SSc, highlighting the potential pathogenic role of inflammation and chronic stimulation-mediated “functional adaptation” of immune cells.

Serum levels of soluble programmed death-1 (sPD-1) and soluble programmed death ligand 1(sPD-L1) in systemic lupus erythematosus: Association with activity and severity

The programmed cell death-1 (PD-1)/programmed cell death ligand 1 (PD-L1) pathway is an important host immunosuppression mechanism. Soluble PD-1 (sPD-1) and PD-L1 (sPD-L1) expression regulates co-inhibitory signals in autoimmune disorders. Here, we evaluated whether serum sPD-1 and sPD-L1 are involved in immune dysfunction and assessed its relationship with SLE. Blood samples were obtained from 130 patients with SLE and 44 healthy controls. Serum sPD-1 and sPD-L1 were tested by enzyme-linked immunosorbent assay (ELISA). Relevant immune parameters were analysed. Both serum sPD-1 and sPD-L1 were significantly higher in the SLE patients than in the controls. A series of severe disease clinical manifestations and laboratory features such as presence of decreased complement component 3, complement component 4 and SLEDAI >8 were associated with elevated sPD-1 and sPD-L1. Our study suggests that abnormal sPD-1 and sPD-L1 expression may be involved in the imbalance of immune regulation in SLE.

The PD-1/PD-L pathway in rheumatic diseases

BACKGROUND/PURPOSE

Autoimmune diseases are diseases in which the body produces an abnormal immune response to self-antigens and damages its own tissues. Programmed death-1 (PD-1) and its ligands (PD-Ls) have been discovered to be important negative regulators of the immune system, playing crucial roles in autoimmunity.

METHODS

We analyzed the existing scientific literature dealing with this issue. In this review, the PD-1/PD-L pathway in the genetic susceptibility to and pathogenesis of rheumatic diseases is discussed. The PD-1/PD-L pathway might be helpful for diagnosing, evaluating the disease activity of and treating rheumatic diseases.

RESULTS

PD-1/PD-L gene polymorphisms are associated with a genetic predisposition to rheumatic disorders, which can provide reference information for diagnosis and disease activity. The conclusion of the crucial role of the PD-1/PD-L pathway in the pathogenesis of rheumatic diseases is consistent, but the details remain controversial. In some animal models, manipulating the PD-1/PD-L pathway could decrease disease severity. PD-1/PD-Ls may enable us to develop new therapeutics for patients with rheumatic diseases in the future.

CONCLUSION

The PD-1/PD-L pathway plays crucial roles in rheumatic disease. More work is needed to provide a better mechanistic understanding of the PD-1/PD-L pathway and to facilitate the precise therapeutic manipulation of this pathway.

The Co-inhibitor BTLA Is Functional in ANCA-Associated Vasculitis and Suppresses Th17 Cells

Objectives: The activation and inhibition of T-cells has been well-studied under physiological conditions. Co-inhibition is an important mechanism to keep effector T-cells in check. Co-inhibitors mediate peripheral self-tolerance and limit the immune response. Dysfunctional co-inhibition is associated with loss of T-cell regulation and induction of autoimmunity. Therefore, we investigated the co-inhibitor B- and T-Lymphocyte attenuator (BTLA) in ANCA-associated vasculitis (AAV). Methods: Fifty-six AAV patients and 32 healthy controls (HC) were recruited. Flow cytometry was performed to investigate the expression of BTLA on T-cells. Double negative T-cells were defined as CD3⁺CD4^-CD8^-. To assess the functionality of BTLA, CFSE-labeled T-cells were stimulated in presence or absence of an agonistic anti-BTLA antibody. In addition, impact of BTLA-mediated co-inhibition on Th17 cells was studied. Results: AAV patients in remission had a decreased expression of BTLA on double negative T-cells (CD3⁺CD4^-CD8^-). On all other subtypes of T-cells, expression of BTLA was comparable to healthy controls. TCR-independent stimulation of T-cells resulted in down-regulation of BTLA on Th cells in AAV and HC, being significantly lower in HC. Co-inhibition via BTLA led to suppression of T-cell proliferation in AAV as well as in HC. As a result of BTLA mediated co-inhibition, Th17 cells were suppressed to the same extent in AAV and HC. Conclusion: BTLA expression is altered on double negative T-cells but not on other T-cell subsets in quiescent AAV. BTLA-induced co-inhibition has the capacity to suppress Th17 cells and is functional in AAV. Thus, BTLA-mediated co-inhibition might be exploited for future targeted therapies in AAV.

Stimulatory and Inhibitory Co-signals in Autoimmunity

Co-receptors cooperatively regulate the function of immune cells to optimize anti-infectious immunity while limiting autoimmunity by providing stimulatory and inhibitory co-signals. Among various co-receptors, those in the CD28/CTLA-4 family play fundamental roles in the regulation of lymphocytes by modulating the strength, quality, and/or duration of the antigen receptor signal. The development of the lethal lymphoproliferative disorder and various tissue-specific autoimmune diseases in mice deficient for CTLA-4 and PD-1, respectively, clearly demonstrates their pivotal roles in the development and the maintenance of immune tolerance. The recent success of immunotherapies targeting CTLA-4 and PD-1 in the treatment of various cancers highlights their critical roles in the regulation of cancer immunity in human. In addition, the development of multifarious autoimmune diseases as immune-related adverse events of anti-CTLA-4 and anti-PD-1/PD-L1 therapies and the successful clinical application of the CD28 blocking therapy using CTLA-4-Ig to the treatment of arthritis assure their crucial roles in the regulation of autoimmunity in human. Accumulating evidences in mice and humans indicate that genetic and environmental factors strikingly modify effects of the targeted inhibition and potentiation of co-signals. In this review, we summarize our current understanding of the roles of CD28, CTLA-4, and PD-1 in autoimmunity. Deeper understandings of the context-dependent and context-independent functions of co-signals are essential for the appropriate usage and the future development of innovative immunomodulatory therapies for a diverse array of diseases.

The Diverse Function of PD-1/PD-L Pathway Beyond Cancer

The recent success of PD-1 and PD-L1 blockade in cancer therapy illustrates the important role of the PD-1/PD-L1 pathway in the regulation of antitumor immune responses. However, signaling regulated by the PD-1/PD-L pathway is also associated with substantial inflammatory effects that can resemble those in autoimmune responses, chronic infection, and sepsis, consistent with the role of this pathway in balancing protective immunity and immunopathology, as well as in homeostasis and tolerance. Targeting PD-1/PD-L1 to treat cancer has shown benefits in many patients, suggesting a promising opportunity to target this pathway in autoimmune and inflammatory disorders. Here, we systematically evaluate the diverse biological functions of the PD-1/PD-L pathway in immune-mediated diseases and the relevant mechanisms that control these immune reactions.

Programmed cell death 1 gene polymorphism as a possible risk for systemic lupus erythematosus in Egyptian females

Systemic lupus erythematosus (SLE) is a multisystem autoimmune disease with a suggested genetic basis. The newly identified human programmed cell death 1 gene could be associated with SLE susceptibility. We aimed to investigate the association between programmed cell death 1 polymorphism (PD1.3G/A (rs11568821) and PD1.5C/T (rs2227981)) with the risk of SLE in the Egyptian female population. This retrospective case-control study included 150 Egyptian females; 70 patients diagnosed to have SLE and 80 age-matched healthy controls. The two single nucleotide polymorphisms of the pdcd1 gene were genotyped by allelic discrimination through TaqMan real-time polymerase chain reaction. The PD1.3GG genotype and G allele as well as the PD1.5CC genotype were significantly more frequent in SLE patients (67.1%; p = 0.023, 82.1%; p = 0.0021, 62.9%; p = 0.0287 respectively). The GC haplotype was the most common haplotype among SLE patients (70.77%) with a reported significant linkage disequilibrium between the two studied polymorphisms (p = 0.0041). Although most of the studies showed significant association of SLE with the minor alleles, we reported a significant association between the dominant genotypes (PD1.3GG and PD1.5CC) as well as the major G allele with the risk of SLE among Egyptian females.

Cutaneous lupus associated with pembrolizumab therapy for advanced melanoma: a report of three cases

Checkpoint blockade immunotherapy has revolutionized the treatment of advanced melanoma, with impressive survival benefits attained through upregulation of the anticancer immune response. Blockade of regulatory checkpoint molecules can, however, also result in aberrant immune activation leading to undesirable inflammation and autoimmunity. Although many genetic determinants have been described in patients with primary autoimmune diseases, it is uncertain whether patients developing autoimmune skin disease as an adverse effect of anti-PD-1 therapy share the same genetic risks. Furthermore, it is also unclear whether treatment with these agents can result in the unveiling of underlying 'silent' autoimmunity resulting in chronic inflammatory disease. We report three cases of cutaneous lupus associated with pembrolizumab therapy for advanced melanoma. One patient had a previous diagnosis of histologically proven discoid lupus erythematosus, well-controlled without treatment for over 2 years, which flared on first exposure to pembrolizumab. The remaining two patients had no previous history of autoimmune disease; both developed cutaneous eruptions, histologically and immunohistologically, in keeping with subacute cutaneous lupus following treatment with pembrolizumab. Our report bolsters what is currently an exceedingly small body of evidence documenting the development of cutaneous lupus in the setting of pembrolizumab therapy. Our third case specifically documents an otherwise unreported severe reflare of previously diagnosed, quiescent discoid lupus erythematosus in the setting of pembrolizumab, vividly highlighting the potential for autoimmune and specifically, lupus reactivation in the setting of anti-PD-1 therapy.

BTLA Expression on Th1, Th2 and Th17 Effector T-Cells of Patients with Systemic Lupus Erythematosus Is Associated with Active Disease

An imbalanced T-cell homeostasis plays an important role in the pathogenesis of systemic lupus erythematosus (SLE). Co-stimulatory and co-inhibitory molecules regulate T-cell differentiation, survival, and cytokine production. B- and T-lymphocyte attenuator (BTLA) is a co-inhibitory molecule which negatively regulates T-cell activation. The aim of this study was to investigate BTLA expression on regulatory and effector CD4⁺ T-cells in SLE patients with and without lupus nephritis (LN) during active and inactive disease. Therefore, peripheral blood of forty-one SLE patients and twenty-one healthy controls (HC) was phenotypically analyzed. Next, ex vivo stimulated T-cells were analyzed for the expression of BTLA on Th1-, Th2-, and Th17-effector cells by flow cytometry. Renal involvement was defined as biopsy-proven LN. Disease activity was assessed by SLE disease activity index (SLEDAI). Percentages of peripheral unstimulated BTLA⁺ CD4⁺ T-cells were significantly decreased in SLE patients with active disease. However, ex vivo stimulated Th1, Th2, and Th17 effector T-cells, expressed increased percentages of BTLA expression in active disease. In contrast, the BTLA expression on CD4⁺CD25⁺⁺CD127⁻ regulatory T-cells was not significantly different. BTLA seems to be an important co-inhibitory molecule in the T-cell homeostasis of patients with systemic lupus erythematosus and crucial for disease activity.

Anti-PD-1 Immunotherapy May Induce Interstitial Nephritis With Increased Tubular Epithelial Expression of PD-L1

Introduction

Novel anticancer therapies include anti–programmed cell death protein-1 (PD-1) and anti–programmed death ligand-1 (PD-L1) drugs. These novel medications have side effects in different organs, including the kidney. The most common adverse effect in the kidney is acute interstitial nephritis (AIN). No diagnostic criteria are available to distinguish AIN associated with anti–PD-1 therapy from other AINs.

Methods

Kidney biopsy specimens from patients on anti–PD-1 therapy were stained with antibodies to PD-1 and PD-L1. Herein we report morphologic and immunohistochemical findings in 15 patients who received anti–PD-1 therapy and developed acute kidney injury requiring a kidney biopsy.

Results

Among these patients, 9 had AIN and 6 had no AIN but showed acute tubular necrosis (ATN). Immunohistochemistry with antibodies to PD-1 and PD-L1 was performed on all of these biopsy specimens and on 9 randomly selected biopsy specimens with AIN from patients who did not receive anti–PD-1 medications, as well as 9 patients with lupus nephritis and active-appearing interstitial inflammation. There was weak staining for PD-1 in T cells in all patients with AIN and lupus; however, tubular epithelial cell membrane staining for PD-L1 was seen only in patients with anti–PD-1 therapy−associated AIN, and not in patients with anti–PD-1 therapy−associated ATN, and not in those with AIN secondary to other medications, or patients with lupus nephritis.

Conclusion

We propose that immunohistochemistry with PD-L1 could be a useful tool to differentiate AIN associated with anti–PD-1 therapy from other AINs.

Kidney-infiltrating T cells in murine lupus nephritis are metabolically and functionally exhausted

While T cells are important for the pathogenesis of systemic lupus erythematosus (SLE) and lupus nephritis, little is known about how T cells function after infiltrating the kidney. The current paradigm suggests that kidney-infiltrating T cells (KITs) are activated effector cells contributing to tissue damage and ultimately organ failure. Herein, we demonstrate that the majority of CD4+ and CD8+ KITs in 3 murine lupus models are not effector cells, as hypothesized, but rather express multiple inhibitory receptors and are highly dysfunctional, with reduced cytokine production and proliferative capacity. In other systems, this hypofunctional profile is linked directly to metabolic and specifically mitochondrial dysfunction, which we also observed in KITs. The T cell phenotype was driven by the expression of an "exhausted" transcriptional signature. Our data thus reveal that the tissue parenchyma has the capability of suppressing T cell responses and limiting damage to self. These findings suggest avenues for the treatment of autoimmunity based on selectively exploiting the exhausted phenotype of tissue-infiltrating T cells.

Association of PD-1 gene with outcome of hepatitis C virus infection

Primary hepatitis C virus infection might be spontaneously cleared or become chronic. Polymorphisms in immune regulatory genes might influence the outcome. The aim of this study was to determine the frequency of genotypes and alleles of PD-1.3 and PD-1.5 gene loci in HCV infected patients and their association with the disease outcome. In this study 167 patients with chronic hepatic C and 42 individuals whose infection was spontaneously cleared, and a healthy control group comprising of 300 participants were included. The presence of chronic or spontaneously cleared infection amongst the participants was determined in advance by serologic and molecular methods. Genomic DNA was extracted using salting out method. PD-1 gene polymorphisms assay was performed using PCR-RFLP method. The frequency of alleles of PD-1.3 gene locus was significantly higher in the spontaneously cleared HCV infected group (P = 0.03) as well as the healthy control group (P = 0.04) in comparison to the chronic infected participants. In the case of PD-1.5 locus, there was no association between the frequency of inherited genotype or alleles and HCV infection outcome amongst the three groups. Haplotype analysis showed no statistically significant differences in the frequencies of different haplotypes between the three studied groups. Our finding collectively inferred that individuals with A allele at PD-1.3 locus might clear HCV infection more frequently than those with T allele. Instead, polymorphisms at PD-1.5 locus as well as haplotypes emerged from PD-1.3 G/A and PD-1.5 C/T might not be significant in the HCV infection outcome.

Association of the Interleukin-6 rs1800795 Polymorphism with Type 2 Diabetes Mellitus in the Population of the Island of Crete, Greece

BACKGROUND

Interleukin 6 (IL-6), a proinflammatory cytokine, is elevated in patients with type 2 diabetes (T2D), and is considered an independent predictor of T2D. IL-6 single-nucleotide polymorphisms (SNPs) have been associated with higher levels of IL-6. This study investigated the role of an IL-6 gene polymorphism and its possible association to T2D in the genetically homogeneous Greek population of the island of Crete.

MATERIALS AND METHODS

A total of 144 patients with T2D and 180 controls, all Cretans, selected from the Diabetes Clinic and the Department of Internal Medicine at the University Hospital of Heraklion, Crete, Greece, were genotyped for the IL-6 -174G>C (rs1800795) SNP by the restriction fragment length polymorphism method.

RESULTS

The G/C genotype and the minor allele C of the IL-6 rs1800795 SNP were more common in individuals with T2D than controls (p = 0.004, odds ratio [OR] = 1.98, 95% confidence interval [CI]: 1.24-3.18 and p = 0.011, OR = 1.59, 95% CI: 1.11-2.26, respectively).

CONCLUSION

An association of the rs1800795 SNP of the IL-6 gene with T2D has been detected for the first time in Cretans. The present results, in combination with those presented previously from different ethnic/racial populations, highlight the necessity of comparative studies among different ethnic/racial populations to detect genetic characteristics and associations with T2D.

Programmed death ligand 1 promotes lymph node metastasis and glucose metabolism in cervical cancer by activating integrin β4/SNAI1/SIRT3 signaling pathway

Although PD-L1 has been shown to play a well-characterized role in inhibiting antitumor immunity via engagement of its receptor PD-1 in T lymphocytes, little is known about the tumor cell-intrinsic function of PD-L1 and its association with prognosis. Here, we investigate this issue and dissect the molecular mechanisms underlying the role of PD-L1 in glucose metabolism, proliferation, migration, and invasion in human cervical cancer cells. As a result, we found that PD-L1 overexpression in cervical cancer cells increases glucose metabolism and metastasis-related behaviors. Mechanistically, PD-L1 bound directly to integrin β4 (ITGB4), activating the AKT/GSK3β signaling pathway and consequently inducing the expression of the transcriptional repressor SNAI1. SNAIL in turn influenced the expression of genes involved in the epithelial-to-mesenchymal transition and regulated glucose metabolism by inhibiting SIRT3 promoter activity. High expression of PD-L1 and ITGB4 in human cervical carcinomas was significantly associated with lymph node metastasis and poor prognosis. Finally, ¹⁸F-fluorodeoxyglucose microPET/CT and bioluminescence imaging analyses of cervical xenograft tumors in mice revealed that PD-L1 overexpression markedly increases tumor glucose uptake and promotes lymph node metastasis. Together, these results demonstrate that PD-L1 can promote the growth and metastasis of cervical cancer by activating the ITGB4/SNAI1/SIRT3 signaling pathway, and also suggest the possibility of targeting PD-L1 and its downstream effectors as a potential approach for interfering with cervical cancer growth and metastasis.

Analysis of PD-1 and Tim-3 expression on CD4+ T cells of patients with rheumatoid arthritis; negative association with DAS28

Expression of T cell immunoglobulin and mucin-domain containing-3 (Tim-3) and programmed cell death-1 (PD-1) was studied on CD4⁺ T cells of patients with rheumatoid arthritis (RA). Association of Tim-3 and PD-1 expression with disease activity of RA patients was also addressed. A total of 37 RA patients and 31 sex- and age-matched healthy controls were included in this study. Disease activity of RA patients was determined by Disease Activity Score of 28 joints scoring system (DAS28). A three-color flow cytometry method was applied to determine the frequency of Tim-3⁺/PD-1⁺/CD4⁺ T cells. To measure the cytokine production, peripheral blood mononuclear cells (PBMCs) were stimulated with PMA/ionomycin. Concentrations of IL-17, IL-10, IFN-γ, and TNF-α were measured in culture supernatants by ELISA. The frequency of PD-1⁺/CD4⁺ and Tim-3⁺/PD-1⁺/CD4⁺ T cells was significantly higher in patients with RA compared to that in controls (p = 0.0013 and p = 0.050, respectively). The percentage of Tim-3⁺/CD4⁺ T cells was similar in patients and controls (p = 0.4498). The RA patients have produced significant higher levels of TNF-α, IL-17, and IFN-γ than those of healthy controls (p = 0.0121, p = 0.0417, and p = 0.0478, respectively). Interestingly, an inverse correlation was found between the frequency of Tim-3⁺/CD4⁺ cells and DAS28 of RA patients (r = - 0.4696, p = 0.0493). Similarly, the percentage of Tim-3⁺/PD-1⁺/CD4⁺ T cells was also revealed an inverse correlation with DAS28 (r = - 0.5268, p = 0.0493). Moreover, significant positive correlations were detected between the concentrations of TNF-α (r = 0.6418, p = 0.0023) and IL-17 (r = 0.4683, p = 0.0373) with disease activity of RA patients. Our results indicate that Tim-3 and PD-1 are involved in immune dysregulation mechanisms of rheumatoid arthritis and could be considered as useful biomarkers for determination of disease activity and progression.

Programmed cell death-1 pathway inhibitors in genitourinary malignancies: specific side-effects and their management

PURPOSE OF REVIEW

Immune checkpoint inhibitors such as those that target the programmed cell death (PD)-1 pathway harness the host immune system to elicit an antitumor response. Their remarkable clinical benefit has led to regulatory approvals in several malignancies including the genitourinary cancers, renal cell carcinoma, and urothelial carcinoma. This review will focus on the management of the toxicities encountered with these agents.

RECENT FINDINGS

Although generally well tolerated, a small proportion of patients (10-20%) treated with PD-1 directed agents as monotherapy can develop severe autoimmune manifestations, also known as, immune-related adverse events. These include but are not limited to rashes, pneumonitis, endocrinopathy, colitis, and immune-mediated hepatic dysfunction. Combining these agents with the anti-CTLA-4 antibody ipilimumab can be associated with a higher incidence of these toxicities. Early initiation of immunosuppression with corticosteroids and other agents when needed can help mitigate these toxicities and to date has not been shown to compromise their clinical benefit.

SUMMARY

The development of immune checkpoint inhibitors represents significant advances in anticancer therapy but their efficacy may come at the cost of autoimmune toxicities secondary to their induction of the immune system. Early recognition of these effects and aggressive upfront management is essential to safely administer these agents in routine clinical practice.

Increased Expression and Modulated Regulatory Activity of Coinhibitory Receptors PD-1, TIGIT, and TIM-3 in Lymphocytes From Patients With Systemic Sclerosis

OBJECTIVE

Immune dysfunction is an important component of the disease process underlying systemic sclerosis (SSc), but the mechanisms contributing to altered immune cell function in SSc remain poorly defined. This study was undertaken to measure the expression and function of the coinhibitory receptors (co-IRs) programmed cell death 1 (PD-1), T cell immunoglobulin and ITIM domain (TIGIT), T cell immunoglobulin and mucin domain 3 (TIM-3), and lymphocyte activation gene 3 (LAG-3) in lymphocyte subsets from the peripheral blood of patients with SSc.

METHODS

Co-IR expression levels on subsets of immune cells were analyzed using a 16-color flow cytometry panel. The functional role of co-IRs was determined by measuring cytokine production after in vitro stimulation of SSc and healthy control peripheral blood mononuclear cells (PBMCs) in the presence of co-IR-blocking antibodies. Supernatants from cultures of stimulated PBMCs were added to SSc fibroblasts, and their impact on fibroblast gene expression was measured. Mathematical modeling was used to reveal differences between co-IR functions in SSc patients and healthy controls.

RESULTS

Levels of the co-IRs PD-1 and TIGIT were increased, and each was coexpressed, in distinct T cell subsets from SSc patients compared to healthy controls. Levels of TIM-3 were increased in SSc natural killer cells. PD-1, TIGIT, and TIM-3 antibody blockade revealed patient-specific roles of each of these co-IRs in modulating activation-induced T cell cytokine production. In contrast to healthy subjects, blockade of TIGIT and TIM-3, but not PD-1, failed to reverse inhibited cytokine production in SSc patients, indicating that enhanced T cell exhaustion is present in SSc. Finally, cytokines secreted in anti-TIM-3-treated PBMC cultures distinctly changed the gene expression profile in SSc fibroblasts.

CONCLUSION

The altered expression and regulatory capacity of co-IRs in SSc lymphocytes may contribute to disease pathophysiology by modulating the cytokine-mediated cross-talk of immune cells and fibroblasts at sites of inflammation and/or fibrosis.

Meta-analysis of programmed cell death 1 polymorphisms with systemic lupus erythematosus risk

The association of polymorphisms in programmed cell death 1 (PDCD1) gene with systemic lupus erythematosus (SLE) risk is inconsistent across different studies. This meta-analysis is aimed to provide reliable evidence to the association of five common PDCD1 polymorphisms (PD1.1, PD1.2, PD1.3, PD1.5 and PD1.6) with SLE risk. A total of 28 studies with 4,344 SLE cases and 5,474 healthy controls were included in this meta-analysis. PD1.3 polymorphism was significantly associated with SLE in the overall population (A vs. G: OR = 1.35, 95% CI = 1.12-1.63; GA vs.GG: OR = 1.41, 95% CI = 1.12-1.76; AA+GA vs. GG: OR = 1.41, 95% CI = 1.13-1.7). In the stratified analyses based on ethnicity, we found a significant association in Caucasians and in Mexicans. In the subgroup analyses by gender, a significant association was found between PD1.3 polymorphism and SLE risk in males. The results also suggested an association between the PD1.6 polymorphism and decreased SLE risk (A vs. G: OR = 0.84, 95% CI = 0.73-0.96). Our meta-analysis revealed that PD1.3 polymorphism may increase the susceptibility to SLE, particularly in Caucasians, while PD1.6 may be a protective factor to SLE.

Biomarkers for immune-related toxicities of checkpoint inhibitors: current progress and the road ahead

INTRODUCTION

Immune checkpoint pathways are key immune regulatory pathways that play a physiologic role in maintaining immune-homeostasis and are often co-opted by cancer cells to evade the host immune system. Recent developments in cancer immunotherapy, mainly drugs blocking the immune checkpoint pathways, have revolutionized the treatment paradigm for many solid tumors. A wide spectrum of immune-related adverse events (irAEs) have been described with the use of these agents which necessitate treatment with immunosuppression, lead to disruption of therapy and can on occasion be life-threatening. There are currently no clinically validated biomarkers to predict the risk of irAEs. Areas covered: In this review, the authors describe the current progress in identifying biomarkers for irAEs and potential future directions. Literature search was conducted using PubMed-MEDLINE, Embase and Scopus. In addition, abstracts from major conference proceedings were reviewed for relevant content. Expert commentary: The discovery of biomarkers for irAEs is currently in its infancy, however there are a lot of promising candidate biomarkers that are currently being investigated. Biomarkers that can identify patients at a higher risk of developing irAEs or lead to early detection of autoimmune toxicities are crucial to optimize patient selection for immune-oncology agents and to minimize toxicity with their use.

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.

Elevated serum autoantibodies against co-inhibitory PD-1 facilitate T cell proliferation and correlate with disease activity in new-onset systemic lupus erythematosus patients

Background

Programmed cell death protein 1 (PD-1) plays an important role in immune response regulation as a co-inhibitory signal during T cell activation. However, there is little known about the serum autoantibody profile of PD-1 in systemic lupus erythematosus (SLE), a disease characterized by the breakdown of immune tolerance to self-antigens and an excessive production of autoantibodies. Thus, we aim to investigate the serum levels and function of anti-PD-1 in patients with new-onset SLE.

Methods

Serum levels of anti-PD-1 IgG and IgM isotypes were detected in new-onset SLE patients (n = 90), rheumatoid arthritis (n = 50), primary Sjogren’s syndrome (n = 50), ankylosing spondylitis (n = 25), and healthy controls (HC) (n = 80) using an enzyme-linked immunosorbent assay (ELISA). The correlation of anti-PD-1 with clinical characteristics and laboratory parameters of patients with new-onset SLE was analyzed. The effects of purified anti-PD-1 IgG from SLE patients on T cell proliferation were measured using flow cytometry.

Results

The data revealed increased levels of anti-PD-1 IgG, but not IgM, especially in new-onset SLE patients, and the positive rate of anti-PD-1 IgG was 30 (33.3%). The level of anti-PD-1 IgG was closely associated with malar rash (OR = 15.773), arthritis (OR = 22.937), serositis (OR = 16.008), hematological (OR = 35.187), renal (OR = 8.306), and neurological involvement (OR = 37.282). Moreover, the serum levels of anti-PD-1 IgG were positively correlated with the SLE disease activity index (SLEDAI) score (r = 0.296, p = 0.0046) and the erythrocyte sedimentation rate (ESR) (r = 0.2446, p = 0.0201). In vitro examination showed that purified anti-PD-1 IgG obtained from SLE patients enhanced T cell proliferation when co-cultured with dendritic cells (DCs).

Conclusions

The current study indicates, for the first time, that the serum levels of co-inhibitor autoantibodies against PD-1 are elevated in new-onset SLE patients and are associated with disease activity in SLE. Autoantibodies against PD-1, facilitating T cell proliferation, revealed a new insight into the function of negative regulation signals involved in the pathogenesis of SLE.

Electronic supplementary material

The online version of this article (doi:10.1186/s13075-017-1258-4) contains supplementary material, which is available to authorized users.

Elevated expression of TIGIT on CD3+CD4+ T cells correlates with disease activity in systemic lupus erythematosus

Objectives

It is well-known that lymphocytes play an important role in systemic lupus erythematosus (SLE). T cell immunoreceptor with Ig and immunoreceptor tyrosine-based inhibitory domains (TIGIT) is one of immunosuppressive costimulatory molecules that mediates an inhibitory effect. However, its roles in SLE are poorly understood. This study was designed to investigate the correlation between the frequencies of TIGIT-expressing CD3⁺CD4⁺ T lymphocytes and SLE.

Methods

Patients with SLE were recruited from the First Affiliated Hospital of Nanchang University. Medical history, clinical manifestations, physical examination and laboratory measurements were recorded. The expression of TIGIT on CD3⁺ T lymphocytes, B lymphocytes, monocytes, neutrophils, CD3⁺CD4⁺ T lymphocytes and CD3⁺CD8⁺ T lymphocytes were determined by flow cytometry. The frequencies of TIGIT-expressing CD3⁺CD4⁺ T lymphocytes in patients with SLE were further analyzed for correlations with markers of autoimmune response, inflammation, urine proteins and disease activity in SLE.

Results

The frequency of TIGIT-expressing CD3⁺CD4⁺ T lymphocytes was significantly elevated in SLE patients compared with healthy controls (P < 0.0001). The frequency of TIGIT-expressing CD3⁺CD4⁺ T lymphocytes in patients with SLE was increased significantly in subjects with high anti-dsDNA titer (P = 0.026), high anti-Sm titer (P = 0.026), and high levels of urine microalbumin (P = 0.046). Furthermore, The frequency of TIGIT-expressing CD3⁺CD4⁺ T lymphocytes was found to be positively correlated with the Disease Activity Index (SLEDAI) score in SLE (r² = 0.082; P = 0.044).

Conclusion

In SLE, the frequency of TIGIT-expressing CD3⁺CD4⁺ T lymphocytes was elevated and associated with the disease activity.

PD-1 gene polymorphic variation is linked with first symptom of disease and severity of relapsing-remitting form of MS

Multiple sclerosis (MS) is an inflammatory disease of the central nervous system (CNS), where inflammation, demyelination together with the axonopathy are the cardinal features on pathologic ground, with a combined genetic and environmental background. The associations of PD-1 single nucleotide polymorphisms (SNPs): PD-1.3 (in intron 4), PD-1.5 and PD-1.9 (both in exon 5) with clinical manifestation of MS in 479 south Polish individuals including 203 MS patients were analyzed. Presence of PD-1.5T allele was linked with the first manifestations of disease: diplopia and pyramidal signs - favored pyramidal signs but protected against of diplopia development. Farther, PD-1.3G/PD-1.5C/PD-1.9C haplotype significantly favored whereas GTC protected against diplopia. Besides, GTT haplotype strongly favored non-severe RRMS outcome and ATC haplotype was specific only for these MS patients. Our population-based case-control study, investigating selected three PD-1 SNPs: PD-1.3, PD-1.5 and PD-1.9, revealed that polymorphic variation may be rather disease-modifying than MS risk factor.

Role of PD-1 in Immunity and Diseases

Immunity developed to defend our bodies from foreign particles, including bacteria and viruses. Although effector cells responsible for acquired immunity, mainly T cells, and B cells, are able to distinguish self from non-self, they sometimes attack the body's tissues because of imperfect central tolerance. Several immune check points developed to limit overactivation of these cells. One of the most important immune checkpoints is programmed cell death-1 (PD-1), which is expressed mainly on activated lymphocytes. As its ligands (PD-Ls) are expressed widely in the body and affect the responses against self and foreign antigens, controlling PD-1/PD-L interactions enables the management of several immune-related diseases such as autoimmune disease, virus infection, and cancers. Currently, the strategy of PD-1/ PD-L1 blockade has already been applied to clinical cancer therapy, providing evidences that PD-1 signal is one of the main factors of cancer immune escape in humans. The dramatic efficacy of PD-1 blockade in cancer immunotherapy, promises the control of other immune diseases by PD-1 signal modulation. In this review, we summarize the history of PD-1, subsequent basic studies, and their application to the clinic.

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.

Genetics of Lupus Nephritis: Clinical Implications

Systemic lupus erythematosus is a heterogeneous autoimmune disease marked by the presence of pathogenic autoantibodies, immune dysregulation, and chronic inflammation that may lead to increased morbidity and early mortality from end-organ damage. More than half of all systemic lupus erythematosus patients will develop lupus nephritis. Genetic-association studies have identified more than 50 polymorphisms that contribute to lupus nephritis pathogenesis, including genetic variants associated with altered programmed cell death and defective immune clearance of programmed cell death debris. These variants may support the generation of autoantibody-containing immune complexes that contribute to lupus nephritis. Genetic variants associated with lupus nephritis also affect the initial phase of innate immunity and the amplifying, adaptive phase of the immune response. Finally, genetic variants associated with the kidney-specific effector response may influence end-organ damage and the progression to end-stage renal disease and death. This review discusses genetic insights of key pathogenic processes and pathways that may lead to lupus nephritis, as well as the clinical implications of these findings as they apply to recent advances in biologic therapies.

Polymorphism in programmed cell death 1 gene is strongly associated with lung and kidney allograft survival in recipients from CMV-positive donors

BACKGROUND

Cytomegalovirus (CMV) has a role in chronic rejection and graft loss in kidney transplant (KTx) and lung transplant (LTx) recipients. In addition, donor CMV seropositivity is an independent risk factor for renal graft loss. The anti-CMV response might modulate this risk. Expression of programmed cell death 1 (PD-1), a receptor involved in viral-specific T-cell exhaustion, is influenced by a single nucleotide polymorphism called PD-1.3 (wild-type allele G, variant allele A).

METHODS

We performed a retrospective study to assess the impact of PD-1.3 on graft outcome in donor CMV seropositive (D+) and donor CMV seronegative (D-) KTx and LTx. We also performed a case-control study to evaluate the anti-CMVpp65 response according to genotype.

RESULTS

PD-1.3 was determined in 1,119 KTx and 181 LTx. In 481 D+ KTx, A allele carriers (24%) experienced significantly less graft failure compared with GG carriers (p = 0.001). Multivariate analysis showed that this association was independent of donor and recipient age, acute rejection episodes, and number of human leukocyte antigen mismatches (hazard ratio, 0.381; 95% confidence interval, 0.209-0.696; p = 0.002). Analysis in 85 D+ LTx showed similar results: A allele carriers had better survival (hazard ratio, 0.302; 95% confidence interval, 0.128-0.716; p = 0.006) and greater 6-month forced expiratory volume (71% ± 17% vs 54% ± 16%, p = 0.001). In D- recipients, PD-1.3 did not affect KTx or LTx outcome. Finally, AA recipients had a stronger anti-CMVpp65 T-cell response than matched GG recipients (p = 0.003).

CONCLUSIONS

The A variant allele in PD-1.3 single nucleotide polymorphism improved graft survival in kidney and lung transplant recipients receiving grafts from CMV-positive donors.

Nonoverlapping roles of PD-1 and FoxP3 in maintaining immune tolerance in a novel autoimmune pancreatitis mouse model

PD-1 (programmed-death 1), an immune-inhibitory receptor required for immune self-tolerance whose deficiency causes autoimmunity with variable severity and tissue specificity depending on other genetic factors, is expressed on activated T cells, including the transcription factor FoxP3(+) Treg cells known to play critical roles in maintaining immune tolerance. However, whether PD-1 expression by the Treg cells is required for their immune regulatory function, especially in autoimmune settings, is still unclear. We found that mice with partial FoxP3 insufficiency developed early-onset lympho-proliferation and lethal autoimmune pancreatitis only when PD-1 is absent. The autoimmune phenotype was rescued by the transfer of FoxP3-sufficient T cells, regardless of whether they were derived from WT or PD-1-deficient mice, indicating that Treg cells dominantly protect against development of spontaneous autoimmunity without intrinsic expression of PD-1. The absence of PD-1 combined with partial FoxP3 insufficiency, however, led to generation of ex-FoxP3 T cells with proinflammatory properties and expansion of effector/memory T cells that contributed to the autoimmune destruction of target tissues. Altogether, the results suggest that PD-1 and FoxP3 work collaboratively in maintaining immune tolerance mostly through nonoverlapping pathways. Thus, PD-1 is modulating the activation threshold and maintaining the balance between regulatory and effector T cells, whereas FoxP3 is sufficient for dominant regulation through maintaining the integrity of the Treg function. We suggest that genetic or environmental factors that even moderately affect the expression of both PD-1 and FoxP3 can cause life-threatening autoimmune diseases by disrupting the T-cell homeostasis.

PDCD1 PD-1.3 polymorphism and allergic bronchial asthma in Russian and Buryat patients

OBJECTIVE

The programmed death-1 receptor, PD-1, is a negative regulator of T-cell activation. The PD-1.3 polymorphism of the PD-1 gene (PDCD1) has been previously shown to be associated with several autoimmune and inflammatory disorders including systemic lupus erythematosus and multiple sclerosis. We examined for the first time PD-1.3 association with another inflammatory disease with strong immune component, IgE-mediated bronchial asthma, its severity and its biochemical markers (total serum IgE and IL-4).

METHODS

PD-1.3 G/A was genotyped by PCR-RFLP analysis using two different populations: Caucasian (492 Russian individuals) and Asian (276 Buryat individuals).

RESULTS

We found a significant association of the PD-1.3 polymorphism with IgE-mediated bronchial asthma and total serum IgE level in the Russian population. Combined genotype AA+AG was correlated with risk of developing allergic bronchial asthma (OR = 1.78, 95% CI 1.13-2.78, p = 0.011) and lower concentrations of total serum IgE (p = 0.001) compared with the wild-type genotype GG. However, PD-1.3 was not polymorphic in the Buryat population.

CONCLUSIONS

PD-1.3 polymorphism of the PD-1 gene (PDCD1) may contribute to the development of allergic asthma in the Russians but not in the Buryats. Our results could be helpful for a better understanding of the effect of this polymorphism on the development of diseases with strong immune components.

Counter-regulation of rejection activity against human liver grafts by donor PD-L1 and recipient PD-1 interaction

BACKGROUND & AIMS

Co-inhibitory receptor-ligand interactions fine-tune immune responses by negatively regulating T cell functions. Our aim is to examine the involvement of co-inhibitory receptor-ligand pair PD-1/PD-L1 in regulating rejection after liver transplantation (LT) in humans.

METHODS

PD-L1/PD-1 expression in liver allograft was determined by immunohistochemistry or flow cytometry, and the effect of blockade was studied using graft-infiltrating T cells ex vivo. Five single nucleotide polymorphisms within PD-1 and PD-L1 genes were genotyped in 528 LT recipients and 410 donors, and associations with both early (⩽6months) and late (>6months) acute rejection were analyzed using Cox proportional-hazards regression model. The effect of PD-L1 rs4143815 on PD-L1 expression was analyzed using donor hepatic leukocytes.

RESULTS

PD-L1 was expressed by hepatocytes, cholangiocytes and along the sinusoids in post-transplant liver allografts, and PD-1 was abundantly expressed on allograft-infiltrating T cells. PD-L1 blockade enhanced allogeneic proliferative responses of graft-infiltrating T cells. In the genetic association analysis, donor PD-L1 rs4143815 (CC/CG vs. GG; HR=0.230; p=0.002) and recipient PD-1 rs11568821 (AA/AG vs. GG; HR=3.739; p=0.004) were associated with acute rejection late after LT in multivariate analysis. Recipients carrying the PD-1 rs11568821 A allele who were transplanted with liver grafts of PD-L1 rs4143815 GG homozygous donors showed the highest risk for late acute rejection. PD-L1 rs4143815 is associated with differential PD-L1 expression on donor hepatic dendritic cells upon IFN-γ stimulation.

CONCLUSION

Our data suggest that interplay between donor PD-L1 and recipient PD-1 counter-regulates rejection activity against liver grafts in humans.

Analysis of Programmed Death-1 in Patients with Psoriatic Arthritis

Programmed death-1 (PD-1) is an inhibitory co-receptor that is highly expressed in T lymphocytes that has been shown to downregulate inflammatory responses in several inflammatory diseases including systemic lupus erythematosus and rheumatoid arthritis. Yet, the role of PD-1 in psoriatic arthritis (PsA) has not been studied. In order to fill this gap, we measured the expression levels of PD-1 in peripheral T cells from patients with active disease. Twenty patients and fifteen age-matched healthy control subjects were recruited. The percentage of CD3(+)PD-1(+) T cells was measured by flow cytometry. Despite normal concentration of peripheral T cells, the expression levels of PD-1 were significantly higher in patients compared to healthy controls. Interestingly, among the patients, the expression levels inversely correlated with disease activity measured by disease activity scores (DAS28). PD-1 expression levels strongly correlated with the number of tender and swollen joints, but not with C-reactive protein (CRP) levels or psoriasis area and severity index (PASI). Functionally, in vitro ligation of PD-1 receptor in PsA T cells inhibited interleukin-2 (IL-2) secretion, Akt phosphorylation, and Rap1 activation. These findings suggest that PD-1 might serve as a biomarker for disease activity in PsA and highlight the need for additional studies in order to establish the role of PD-1 in PsA pathogenesis.

PD-L1-expressing neutrophils as a novel indicator to assess disease activity and severity of systemic lupus erythematosus

Background

It is well-known that increased frequency of neutrophils was found in patients with systemic lupus erythematosus (SLE). However, the immunomodulatory roles and mechanisms of neutrophils in SLE are poorly understood.

Methods

Patients with SLE were recruited from the First Affiliated Hospital of Nanchang University. The medical history, clinical manifestations, physical examination, laboratory measurements, therapeutic regimen and treatment response were recorded. The expression of costimulatory molecules including programmed death 1 (PD-1), programmed death ligand 1 (PD-L1), T-cell immunoglobulin and mucin domain–containing protein 3 (Tim-3), CD40, T cell immunoreceptor with Ig and immunoreceptor tyrosine-based inhibitory domains (TIGIT), CD80 and CD86 on neutrophils were determined by flow cytometry. The frequencies of PD-L1-expressing neutrophils in patients with SLE were further analyzed for their correlation with markers of autoimmune response, inflammation, disease activity and severity of SLE.

Results

The frequency of PD-L1-expressing neutrophils was significantly elevated in SLE patients compared to the healthy controls (P < 0.0001). The frequency of PD-L1-expressing neutrophils in patients with SLE was increased significantly in subjects with high ANA titre, high anti-nRNP/Sm, high levels of inflammatory markers and high SLE Disease Activity Index (SLEDAI) score. Furthermore, the percentages of PD-L1-expressing neutrophils were significantly decreased in SLE patients that received a 15-day regular treatment with corticosteroids and immunosuppressive drugs (P = 0.0075).

Conclusion

The frequency of PD-L1-expressing neutrophils is elevates in patients with SLE, correlates with the disease activity and severity of SLE, and may serves as a negative feedback mechanism preventing potential tissue damage caused by excessive autoimmune responses in patients with SLE.

Immune-related adverse events with immune checkpoint blockade: a comprehensive review

Cancer immunotherapy is coming of age; it has prompted a paradigm shift in oncology, in which therapeutic agents are used to target immune cells rather than cancer cells. The first generation of new immunotherapies corresponds to antagonistic antibodies that block specific immune checkpoint molecules cytotoxic T-lymphocyte-associated antigen 4 (CTLA-4), programmed cell death protein (PD-1) and its ligand PD-L1. Targeting these checkpoints in patients living with cancer had led to long-lasting tumour responses. By unbalancing the immune system, these new immunotherapies also generate dysimmune toxicities, called immune-related adverse events (IRAEs) that mainly involve the gut, skin, endocrine glands, liver, and lung but can potentially affect any tissue. In view of their undisputed clinical efficacy, anti-CTLA-4 and anti-PD-1 antibodies are entering in the routine oncological practice, and the number of patients exposed to these drugs will increase dramatically in the near future. Although steroids can be used to treat these IRAEs, the associated immunosuppression may compromise the antitumour response. Oncologists must be ready to detect and manage these new types of adverse events. This review focuses on the mechanisms of IRAE generation, putative relationship between dysimmune toxicity and antitumour efficacy, as a basis for management guidelines.

Soluble PD-1 aggravates progression of collagen-induced arthritis through Th1 and Th17 pathways

INTRODUCTION

The programmed cell death 1 (PD-1) protein is a critical regulator of T-cell activation and is also an important therapeutic target for autoimmune diseases. Little is known about the regulation and functional properties of the soluble PD-1 (sPD-1) variant. The aim of this study was to examine the role of sPD-1 in the regulation of human and murine rheumatoid arthritis (RA).

METHODS

Expression of cytokines and sPD-1 in sera, synovial fluid, and peripheral blood (PB) mononuclear cells of patients with RA were analyzed by enzyme-linked immunosorbent assay and quantitative polymerase chain reaction. PD-1 function was assessed in PB T cells after stimulation of the cells with anti-CD3 and PD-L1-Fc to crosslink PD-1. Recombinant PD-1-Fc was injected intraperitoneally into DBA/1 mice with collagen-induced arthritis (CIA) to analyze the function of sPD-1 in vivo.

RESULTS

High concentrations of sPD-1 were found in sera and synovial fluid of patients with RA. The levels of serum sPD-1 were significantly correlated with titers of rheumatoid factor (RF) (r = 0.306, p = 0.005) and 28-joint Disease Activity Score (r = 0.545, p < 0.001). Further characterization of sPD-1 revealed that it functionally blocked the inhibitory effect of membrane-bound PD-1 on T-cell activation. Interferon γ, tumor necrosis factor α, and interleukin 17A were identified as inducers of sPD-1 in vitro. Moreover, PD-1-Fc enhanced proinflammatory cytokine expression, generation of Th1 cells and Th17 cells, and joint pathology in a CIA model.

CONCLUSIONS

sPD-1 regulates peripheral T-cell responses in both human and murine RA. Thus, sPD-1 may represent an additional biomarker or target in immunomodulatory therapy for RA.