Extracorporeal photopheresis affects co-stimulatory molecule expression and interleukin-10 production by dendritic cells in graft-versus-host disease patients

Extracorporeal Photopheresis in Dermatological Diseases

Extracorporeal photopheresis (ECP) is an apheresis procedure that is conventionally used as a first-line treatment for cutaneous and leukemic subtypes of T-cell lymphoma, such as Sezary's syndrome and mycosis fungoides. Over the past three decades, its immunotherapeutic properties have been tested on a variety of autoimmune conditions, including many dermatologic diseases. There is ample evidence of ECP's ability to modify leukocytes and alter cytokine production for certain dermatologic diseases that have been refractory to first-line treatments, such as atopic dermatitis. However, the evidence on the efficacy of ECP for the treatment of these dermatologic diseases is unclear and/or lacks sufficient evidence. The purpose of this paper is to review the literature on the utilization and clinical efficacy of ECP in the treatment of several [autoimmune] dermatologic diseases and discuss its applications, guidelines, recommendations, and future implementation for dermatologic diseases.

Extracorporeal photopheresis as an immunomodulatory treatment modality for chronic GvHD and the importance of emerging biomarkers

Haematopoietic stem cell transplantation (HSCT) is the treatment of choice for malignant haematological diseases. Despite continuous improvements in pre- and post-transplantation procedures, the applicability of allo-HSCT is limited by life-threatening complications such as graft-versus-host disease (GvHD), engraftment failure, and opportunistic infections. Extracorporeal photopheresis (ECP) is used to treat steroid resistant GvHD with significant success. However, the molecular mechanisms driving its immunomodulatory action, whilst preserving immune function, require further understanding. As ECP is safe to administer with few significant adverse effects, it has the potential for earlier use in the post-HSCT treatment of GvHD. Thus, further understanding the immunomodulatory mechanisms of ECP action may justify more timely use in clinical practice, as well as identify biomarkers for using ECP as first line or pre-emptive GvHD therapy. This review aims to discuss technical aspects and response to ECP, review ECP as an immunomodulatory treatment modality for chronic GvHD including the effect on regulatory T cells and circulating vs. tissue-resident immune cells and consider the importance of emerging biomarkers for ECP response.

Optimierung der extrakorporalen Photopherese

Die Extrakorporale Photopherese ist ein etabliertes Therapieverfahren für Patienten mit T-Zell vermittelten Erkrankungen. Dabei besteht das Verfahren aus der Gewinnung autologer mononukleärer Zellen, deren Behandlung mit 8-Methoxypsoralen und UVA-Licht und die Retransfusion der behandelten Zellen.

Die Wirkmechanismen der Photopherese sind zwar noch nicht vollständig geklärt, ein zentraler Mechanismus stellt jedoch die Apoptose mononukleärer Zellen dar. Das Ziel der Studie war eine Optimierung der Photopherese im Hinblick auf die Behandlung der Zellen mit 8-Methoxypsoralen/UVA und der daraus induzierten verstärkten Apoptose der Lymphozyten. Dabei sind einige Faktoren bekannt, welche die Effektivität der 8-Methoxypsoralen/UVA-Behandlung der Zellen beeinflussen können, wie z.B. der Hämatokrit oder die UVA-Dosis. Unser Fokus lag auf der Verfügbarkeit der photoaktiven Substanz und dem Einfluss der Zellsuspensionsmatrix auf die Apoptose der Lymphozyten.

Die Verfügbarkeit von 8-Methoxypsoralen für die Aufnahme in die Zellen reduzierte sich durch Absorption an Kunststoffe der Bestrahlungssysteme sowie durch Bindung an Proteine bei der Verwendung von autologem Plasma bei der Suspendierung der Zellen. Eine Steigerung der Zugabe von 8-Methoxypsoralen auf 340 ng/mL anstelle von 200 ng/mL führte zu einem Anstieg der T-Zell Apoptose, die sich unter Verwendung von physiologischer Kochsalzlösung als Zellsuspensionsmatrix weiter erhöhte. Eine Anpassung des Verfahrens mit NaCl anstelle von Plasma und die Verwendung einer höheren 8-Methoxypsoralen Konzentration führte zu einer gesteigerten Apoptoseinduktion der T-Zellen. Inwiefern sich eine Erhöhung der Apoptose auf die klinische Wirksamkeit auswirkt, bedarf hingegen noch weiterer klinischen Untersuchungen.

Apoptosis induction by extracorporeal photopheresis is enhanced by increasing the 8-methoxypsoralen concentration and by replacing plasma with saline

BACKGROUND

Extracorporeal photopheresis (ECP), an apheresis-based therapy for various immunological diseases, works mainly by inducing apoptosis in lymphocytes. Several factors influence the efficacy of ECP with the photosensitizer 8-methoxypsoralen (8-MOP) and ultraviolet light A (UVA). This study aimed to optimize treatment by varying the 8-MOP starting concentration and the cell suspension medium.

MATERIALS AND METHODS

All patients (n = 13) included in this study received photopheresis as medically indicated. Cells collected with a Spectra Optia apheresis system were suspended in plasma or physiological saline (NaCl) and incubated with 200 ng/ml versus 340 ng/ml photosensitizer before UVA irradiation (Macogenic G2 or UVA PIT system). Lymphocyte apoptosis and caspase activity were analyzed by flow cytometry and fluorimetry, and residual 8-methoxypsoralen concentrations by liquid chromatography-mass spectrometry.

RESULTS

Raising the 8-MOP starting concentration significantly increased lymphocyte apoptosis, with values of 22% versus 35% (plasma) and 28%-46% (NaCl) at 24 h post-ECP and 37% versus 86% (plasma) and 74% versus 97% (NaCl) at 48 h for 200 ng/ml versus 340 ng/ml. Pre-transfusion residual 8-MOP levels were 168 ng/ml (plasma) and 162 ng/ml (NaCl) versus 290 ng/ml (plasma) and 266 ng/ml (NaCl) for the lower versus higher dose, respectively.

DISCUSSION

Hence, 8-MOP concentration influences the efficacy of photopheresis as lymphocyte apoptosis rates were significantly higher with the higher starting concentration and with NaCl versus plasma. This indicates that increased 8-MOP starting doses and saline as additional suspension medium could help in improving ECP's efficacy.

Validation of an apoptosis assay for extracorporeal photopheresis

OBJECTIVES

This validation study investigated a flow cytometric apoptosis assay according to good manufacturing practice (GMP).

BACKGROUND

Extracorporeal photopheresis (ECP) is a treatment for various immunological diseases and cutaneous T-cell lymphomas. It is based on the induction of apoptosis by 8-methoxypsoralene and ultraviolet A light. The quantification of apoptosis is therefore essential for ECP improvements. However, despite numerous publications on apoptosis, validated technical details are lacking.

METHODS AND MATERIALS

Mononuclear cells were collected by apheresis and treated by ECP or camptothecin. Samples taken before and after ECP were cultured for 24, 48 and 72 h and analysed for apoptosis and viability of T cells and monocytes by flow cytometry with Annexin V and 7-AAD staining. Accuracy of the assay, intra- and inter-assay precision and the pre-analytical and analytical stability of the analytes were the investigated parameters.

RESULTS

Our data indicate that the median intra- and inter-assay precision coefficient of variation for T cells was 3.86% and 4.80%, respectively. Pre-analytical stability of T cells and monocytes was ensured during short-term storage for up to 2 h on ice. After staining, analytical stability was limited to 30 min, likely because of ongoing apoptosis and loss of monocytes due to plastic adhesion.

CONCLUSION

The results of this validation study show that the assay is GMP-compliant and that its reliability, accuracy and precision are acceptable. While pre-analytical stability of the cells was compatible with on-site procedures, our analytical stability data indicate that this assay is not suited for batch mode analysis of ECP products.

Thymopoiesis, Alterations in Dendritic Cells and Tregs, and Reduced T Cell Activation in Successful Extracorporeal Photopheresis Treatment of GVHD

Acute graft-versus-host disease (aGVHD) is a significant complication of allogeneic hematopoietic stem cell transplant (HSCT) and negatively affects T cell reconstitution. Extracorporeal photopheresis (ECP) reduces aGVHD, but the mechanisms remain incompletely understood. Our objective was to examine the impact of ECP on thymopoiesis in pediatric aGVHD and the mechanisms at a cellular and transcriptional level. Sixteen pediatric HSCT patients were recruited: 6 with ECP-treated aGVHD, 5 without aGVHD, and 5 with aGVHD treated with corticosteroids only. Thymopoiesis was evaluated by measuring naive T cells, TRECs, IL-7, and T cell receptor repertoire diversity. Regulatory T cell (Treg) enumeration and function and dendritic cell (DC) enumeration and phenotype were analyzed using flow cytometry. T cell transcriptome analysis was performed on ECP patients after treatment and responders pre- and post-treatment. Four ECP responders demonstrated thymic-dependent T cell recovery, and superior median naïve T cell numbers at 8 and 12 months post-HSCT compared to the aGVHD corticosteroid group. Increased Tregs and Treg suppressive function, reduced cDC/pDC and DC co-stimulatory marker expression in ECP responders suggest upregulated peripheral tolerance; these findings were not observed in partial responders. Responder post-ECP CD3+ T cell transcriptional profile demonstrated 3333 downregulated and 364 upregulated genes, with significant downregulation of ERRα and GαS pathways, and reduced expression of pro-inflammatory and adhesion proteins.

Thymic function improves with successful ECP treatment. ECP reduces T cell activation and impacts peripheral tolerance via DCs and Tregs. Differences in thymic recovery, DC, and Treg cellular patterns and the T cell transcriptome were observed between ECP responders and partial responders and require further validation and investigation in additional patients.

Randomized phase II trial of extracorporeal phototherapy and steroids vs. steroids alone for newly diagnosed acute GVHD

Steroids remain the initial therapy for acute graft-vs.-host disease (AGVHD). Strategies to improve response and minimize steroid exposure are needed. We report results of a randomized, adaptive, Bayesian-designed, phase II trial of prednisone with or without extracorporeal photopheresis (ECP) as an initial therapy for patients with newly diagnosed AGVHD. The primary endpoint was success at day 56 defined as: alive, in remission, achieving AGVHD response without additional therapy, and on <1 mg/kg at day 28 and <0.5 mg/kg on day 56 of steroids. Eighty-one patients were randomized to the ECP arm (n = 51) or steroids alone (n = 30). Median age was 54 years (range: 17-75); 90% had grade II AGVHD and 10% had grades III and IV AGVHD, with skin (85%), upper (22%)/lower (22%) gastrointestinal, and liver (10%) involvement. The ECP arm had a higher probability of success (0.815) and exceeded the predefined threshold for determining the investigational arm promising. ECP was potentially more beneficial than steroids-alone in skin-only AGVHD (response rate: 72% vs. 57%, respectively) than for visceral-organ AGVHD (47% vs. 43%, respectively). The addition of ECP to steroids may result in higher GVHD response as initial therapy for AGVHD, especially for patients with skin-only involvement.

Extracorporeal Photopheresis: A Case of Immunotherapy Ahead of Its Time

Extracorporeal photopheresis (ECP) is a cell-based immunotherapy that involves the reinfusion of autologous leukocytes after exposure to psoralen and UVA. The treatment has been used for over 30 years, at first on patients with cutaneous T-cell lymphoma (CTCL) and later for the management of patients with graft-versus-host disease (GvHD), sclerosing disorders, atopic dermatitis, and other diseases that may share the common driving factor of a pathogenic T-cell clone or clones in blood circulation. Patients with clinical improvement mount an antigen-specific immune response that may have tolerance traits in the case of GvHD or anticlonal cytotoxic characteristics in the case of CTCL. The exact mechanisms that dictate one response or the other are not fully understood, but the evidence accumulated so far indicates that multiple events occur simultaneously and consequentially contribute to the end result. These include contact of cells with the outside (plastics and tubing of the ECP apparatus), exposure to psoralen and UVA that activates platelets, monocytes, and other myeloid cells, the release of damage-associated molecular patterns, differentiation of monocytes into dendritic cells, and generation and successive presentation of numerous antigens after the phagocytosis of apoptotic cells. Once reintroduced, the ECP product increases the frequency and activity of regulatory T cells (Tregs), shifts the systemic cytokine balance, and promotes extravasation of immune cells that together shape the effects of this treatment. In this review, we summarize the seminal work and most recent literature of the therapeutic mechanisms and reflect on future avenues of improvements and applications of ECP.

Treatment of Pediatric Acute Graft-versus-Host Disease-Lessons from Primary Immunodeficiency?

Allogeneic hematopoietic stem cell transplant (HSCT) is used to treat increasing numbers of malignant and non-malignant disorders. Despite significant advances in improved human leukocyte antigens-typing techniques, less toxic conditioning regimens and better supportive care, resulting in improved clinical outcomes, acute graft-versus-host disease (aGvHD) continues to be a major obstacle and, although it principally involves the skin, gastrointestinal tract, and liver, the thymus is also a primary target. An important aim following HSCT is to achieve complete and durable immunoreconstitution with a diverse T-cell receptor (TCR) repertoire to recognize a broad range of pathogens providing adequate long-term adaptive T-lymphocyte immunity, essential to reduce the risk of infection, disease relapse, and secondary malignancies. Reconstitution of adaptive T-lymphocyte immunity is a lengthy and complex process which requires a functioning and structurally intact thymus responsible for the production of new naïve T-lymphocytes with a broad TCR repertoire. Damage to the thymic microenvironment, secondary to aGvHD and the effect of corticosteroid treatment, disturbs normal signaling required for thymocyte development, resulting in impaired T-lymphopoiesis and reduced thymic export. Primary immunodeficiencies, in which failure of central or peripheral tolerance is a major feature, because of intrinsic defects in hematopoietic stem cells leading to abnormal T-lymphocyte development, or defects in thymic stroma, can give insights into critical processes important for recovery from aGvHD. Extracorporeal photopheresis is a potential alternative therapy for aGvHD, which acts in an immunomodulatory fashion, through the generation of regulatory T-lymphocytes (Tregs), alteration of cytokine patterns and modulation of dendritic cells. Promoting normal central and peripheral immune tolerance, with selective downregulation of immune stimulation, could reduce aGvHD, and enable a reduction in other immunosuppression, facilitating thymic recovery, restoration of normal T-lymphocyte ontogeny, and complete immunoreconstitution with improved clinical outcome as the ability to fight infections improves and risk of secondary malignancy or relapse diminishes.

Extracoporeal photopheresis treatment of acute graft-versus-host disease following allogeneic haematopoietic stem cell transplantation

Acute graft-versus-host disease (aGvHD) continues to be a major obstacle to allogeneic haematopoietic stem cell transplantation. Thymic damage secondary to aGvHD along with corticosteroids and other non-selective T lymphocyte-suppressive agents used in the treatment of aGvHD concurrently impair thymopoiesis and negatively impact on immunoreconstitution of the adaptive immune compartment and ultimately adversely affect clinical outcome. Extracorporeal photopheresis (ECP) is an alternative therapeutic strategy that appears to act in an immunomodulatory fashion, potentially involving regulatory T lymphocytes and dendritic cells. By promoting immune tolerance and simultaneously avoiding systemic immunosuppression, ECP could reduce aGvHD and enable a reduction in other immunosuppression, allowing thymic recovery, restoration of normal T lymphopoiesis, and complete immunoreconstitution with improved clinical outcome. Although the safety and efficacy of ECP has been demonstrated, further randomised controlled studies are needed as well as elucidation of the underlying mechanisms responsible and the effect of ECP on thymic recovery.

Concise Review: Mechanisms Behind Apoptotic Cell-Based Therapies Against Transplant Rejection and Graft versus Host Disease

The main limitations to the success of transplantation are the antigraft response developed by the recipient immune system, and the adverse side effects of chronic immunosuppression. Graft-versus-host disease (GVHD) triggered by donor-derived T lymphocytes against the recipient tissues is another serious obstacle in the field of hematopoietic stem cell transplantation. Several laboratories have tested the possibility of promoting antigen (Ag)-specific tolerance for therapy of graft rejection, GVHD, and autoimmune disorders, by developing methodologies that mimic the mechanisms by which the immune system maintains peripheral tolerance in the steady state. It has been long recognized that the silent clearance of cells undergoing apoptosis exerts potent immune-regulatory effects and provides apoptotic cell-derived Ags to those Ag-presenting cells (APCs) that internalize them, in particular macrophages and dendritic cells. Therefore, in situ-targeting of recipient APCs by systemic administration of leukocytes in early apoptosis and bearing donor Ags represents a relatively simple approach to control the antidonor response against allografts. Here, we review the mechanisms by which apoptotic cells are silently cleared by phagocytes, and how such phenomenon leads to down-regulation of the innate and adaptive immunity. We discuss the evolution of apoptotic cell-based therapies from murine models of organ/tissue transplantation and GVHD, to clinical trials. We make emphasis on potential limitations and areas of concern of apoptotic cell-based therapies, and on how other immune-suppressive therapies used in the clinics or tested experimentally likely also function through the silent clearance of apoptotic cells by the immune system. Stem Cells 2016;34:1142-1150.

Infusion of dendritic cells carrying donor lymphocytes treated with 8-methoxypsoralen and ultraviolet A light induces CD19+ IL-10+ regulatory B cells and promotes skin allograft survival

PUVA-SP DCs are immature dendritic cells (imDCs) that have taken up donor splenic lymphocytes treated with 8-methoxypsoralen and ultraviolet A light (PUVA-SPs). Phagocytosis of donor PUVA-SPs does not stimulate phenotype maturation of recipient imDCs, and infusion of PUVA-SP DCs can induce CD4(+)CD25(high)Foxp3(+) regulatory T cells (Treg). However, the regulatory effect of PUVA-SP DCs on B cells is poorly understood. In this study, we compared PUVA-SP DCs with imDCs in terms of lipopolysaccharide (LPS) responsiveness and flow cytometric analysis of interleukin (IL) 10 expression in splenic CD19(+)B cells. Our results demonstrate that PUVA-SP DCs can suppress subsequent LPS-induced DC maturation and that infusion of PUVA-SP DCs, in the absence of an immunosuppressant, significantly promotes skin allograft survival. This effect was associated with up-regulation of circulating regulatory B cells exhibiting preferential IL-10 secretion. Our results suggest that effective treatments involving infusion of PUVA-SP DCs is likely related to the modulation not only of T-cell and Treg functions but also of B-cell and regulatory B-cell (Breg) functions.

Previously Activated Psoralen: A Possible Novel Format of Psoralen Used in the Treatment of Graft-versus-host Disease

Graft-versus-host disease (GVHD) is a lethal complication of allogeneic haematopoietic stem cell transplantation which limits its application. Psoralen was utilized in the treatment of GVHD as a second-line method, which is also known as extracorporeal photochemotherapy (ECP). In the process of ECP, mononuclear cells must be isolated from the body in advance then a photosensitizer, 8-methoxypsoralen (8-MOP, 200 μg/L for the final concentration), would be added to the cell suspension before its exposure to ultraviolet A [UVA; 365 nm, 2J/cm2]. The disposed lymphocytes re-infused into the body account for 5% to 15% of the lymphocytes in the body. The process of ECP is complicated, expensive and very labour intensive, which limits its popularity. We hypothesized that psoralen should be activated by ultraviolet A, and should be kept in activation for a relatively long time before it gets in contact with mononuclear cells. This kind of psoralen is called previously activated psoralen (PAP), which may have the same effects on GVHD as ECP, but would be much easier and economical to work with.

Modulation and Apoptosis of Neutrophil Granulocytes by Extracorporeal Photopheresis in the Treatment of Chronic Graft-Versus-Host Disease

Chronic graft-versus-host disease (cGVHD) is a common side effect of allogeneic stem cell transplantation and a major cause of morbidity and mortality in affected patients. Especially skin, eyes and oral mucosa are affected. This can lead to pain and functional impairment. Extracorporeal photopheresis (ECP) is an effective immunomodulatory therapy with minimal side effects but its mode of action is still largely unknown. The objective of the present study was to examine the effects of ECP on neutrophil granulocytes in patients with cGVHD. Analysis of leukocytes from cGVHD patients obtained from the ECP device during treatment showed that neutrophil granulocytes account for the majority of cells treated during ECP. Neutrophils from healthy donors treated in vitro with 8-methoxypsoralen and UVA light as well as neutrophils from buffy coats of patients with cGVHD treated by ECP showed increased apoptosis and decreased half-life. In remaining non-apoptotic cells chemoirradiation resulted in loss of activation markers and reduced effector functions. This was accompanied by an increase in extracellular arginase-1 activity. Additional comparison of neutrophils isolated from blood of cGVHD patients before and 24h after ECP revealed a decreased half-life and reduction of effector functions of post-ECP neutrophils ex vivo. These observations strongly suggest that ECP induces both apoptosis and physiological changes in neutrophils and that these changes also take place in vivo. This study is the first to show that ECP modulates apoptosis and inflammatory activity in neutrophil granulocytes, indicating that neutrophils may significantly contribute to the overall immunomodulatory effects attributed to this treatment.

The effect of extracorporeal photopheresis on T cell response in chronic graft-versus-host disease

Extracorporeal photopheresis (ECP) is a safe and effective immunoregulatory therapy for steroid-refractory chronic graft-versus-host disease (cGVHD) but its mechanism of action is poorly understood. In this study, we evaluated the effect of ECP in a sample of cGVHD patients. Our data showed that ECP-treated patients had lower CD4 T and B cells, and substantially higher NK cells than untreated patients. T regulatory (Treg) cells were similar between the two groups of patients. Interestingly, Treg cells were higher in ECP-treated patients and ECP-responders who had no history of aGVHD or sclerosis, than in those who had one of them or both. These findings suggest that at least one of the mechanisms of immunomodulation by ECP targets the Treg cell population and that an increase in Treg cells may be associated with response in patients with cGVHD. Together, the results of ECP are different depending on the patients' clinical condition.

Extracorporeal photopheresis after heart transplantation

The addition of extracorporeal photopheresis (ECP) to a standard immunosuppressive drug therapy after heart transplantation in clinical studies has shown to be beneficial, for example, by reducing acute rejection, allograft vasculopathy or CMV infection. However, the protocols varied considerably, have a predetermined finite number of ECP treatments and adjuvant immunosuppressive regimens used in combination with ECP have differed significantly. Furthermore, there are scarce data to guide which patients should be treated with ECP and when or who would benefit further if ECP were to be continued long term to increase the safety by reducing immunosuppressive drug toxicities without losing efficacy. The knowledge of the tolerance-inducing effects of ECP-like upregulation of regulatory T cells and of dendritic cells may allow to develop a strategy to monitor immunomodulation effects of ECP to further identify ECP responders, the optimal individual ECP schedule and whether ECP therapy can replace or reduce immunosuppressive drug therapy.

Extracorporeal photopheresis promotes IL-1β production

Extracorporeal photopheresis (ECP) is a widely used clinical cell-based therapy exhibiting efficacy in heterogenous immune-mediated diseases such as cutaneous T cell lymphoma, graft-versus-host disease, and organ allograft rejection. Despite its documented efficacy in cancer immunotherapy, little is known regarding the induction of immunostimulatory mediators by ECP. In this article, we show that ECP promotes marked release of the prototypic immunostimulatory cytokine IL-1β. ECP primes IL-1β production and activates IL-1β maturation and release in the context of caspase-1 activation in monocytes and myeloid dendritic cells. Of interest, IL-1β maturation by ECP was fully intact in murine cells deficient in caspase-1, suggesting the predominance of an inflammasome-independent pathway for ECP-dependent IL-1β maturation. Clinically, patient analysis revealed significantly increased IL-1β production in stimulated leukapheresis concentrates and peripheral blood samples after ECP. Collectively, these results provide evidence for promotion of IL-1β production by ECP and offer new insight into the immunostimulatory capacity of ECP.

Extracorporeal photopheresis combined with pentostatin in the conditioning regimen for canine hematopoietic cell transplantation does not prevent GVHD

Extracorporeal photopheresis (ECP) and the purine analog pentostatin exert potent immunomodulatory effects. We evaluated the use of these treatment modalities to prevent GVHD in a canine model of unrelated dog leukocyte Ag-mismatched hematopoietic cell transplantation, after conditioning with 920 cGy TBI. We have shown previously in this model that 36/40 dogs given MTX alone as postgrafting immunosuppression engrafted and that 25 of 40 dogs had severe GVHD and median survival of 21 days. In the current study, nine dogs received conditioning with 920 cGy TBI and postgrafting MTX either with ECP on days -2 to -1 alone (n=5) or ECP on days -6 and -5 combined with two doses of pentostatin (days -4 to -3) (n=4). Seven of nine dogs achieved engraftment. Six dogs developed severe acute GVHD (four in the group with ECP alone and two with pentostatin and ECP). We failed to demonstrate a positive impact of ECP and pentostatin for the prevention of GVHD compared with historical control dogs.

Updating ECP action mechanisms

Extracorporeal Photochemotherapy (ECP) consists in illumination of the patient's leukocytes in the presence of 8-Methoxy Psoralen (8-MOP) and its reinjection to the same patient. ECP is responsible for many cellular events, the most important being the induction of cell apoptosis. Apoptosis appears first in lymphocytes and activated lymphocytes (allo or auto) which are more sensitive and undergo faster apoptosis rather than other cells. Monocytes develop apoptosis later. The injection of apoptotic cells induces tolerance in patients with graft versus host disease (GvHD) and acute heart or lung graft rejection. In these patients, phagocytosis of apoptotic cells by antigen-presenting cells (APCs) and in particular dendritic cells is responsible for a shift from Th1 to Th2 immune response, an increase in anti-inflammatory cytokines such as interleukine 10 (IL-10) and Tumor Growth Factor Beta (TGF-β), a decrease in pro-inflammatory cytokines and finally, for the proliferation of regulatory cells. Among CD4/CD25 positive cells, only CD4(+)CD25(hi) are T-regulatory cells (T-regs). One subpopulation of T-regs produces IL-10 and inhibits Th1 CD4 cells, whereas other populations act as suppressors and inhibit the cytotoxic T-cells responsible for organ rejection and GvHD in an antigen specific fashion. It is not clear why the injection of early apoptotic cells induces tolerance in GvHD and organ graft rejection, but in Sézary syndrome, it induces up-regulation of anti-tumor immune response. Immune response modulation (up- or down-regulation) after ECP depends on many factors: early apoptotic cell injection; anti-inflammatory environment; impaired function of dendritic cells; dendritic type 2 cell dominance, lead to immune tolerance, whereas late apoptotic or necrotic cell injection and pro-inflammatory cytokines enhance immune response. Therefore, immune response to ECP depends on various factors responsible for the diversity of its mode of action in different diseases and further investigations are required.

Integrin-driven monocyte to dendritic cell conversion in modified extracorporeal photochemotherapy

Due to clinical efficacy and safety profile, extracorporeal photochemotherapy (ECP) is a commonly used cell treatment for patients with cutaneous T cell lymphoma (CTCL) and graft-versus-host disease (GVHD). The capacity of ECP to induce dendritic antigen-presenting cell (DC)-mediated selective immunization or immunosuppression suggests a novel mechanism involving pivotal cell signalling processes that have yet to be clearly identified as related to this procedure. In this study we employ two model systems of ECP to dissect the role of integrin signalling and adsorbed plasma proteins in monocyte-to-DC differentiation. We demonstrate that monocytes that were passed through protein-modified ECP plates adhered transiently to plasma proteins, including fibronectin, adsorbed to the plastic ECP plate and activated signalling pathways that initiate monocyte-to-DC conversion. Plasma protein adsorption facilitated 54·2 ± 4·7% differentiation, while fibronectin supported 29·8 ± 7·2% differentiation, as detected by DC phenotypic expression of membrane CD80 and CD86, as well as CD36, human leucocyte antigen D-related (HLA-DR) and cytoplasmic CD83. Further, we demonstrate the ability of fibronectin and other plasma proteins to act through cell adhesion via the ubiquitous arginine-glycine-aspartic (RGD) motif to drive monocyte-to-DC differentiation, with high-density RGD substrates supporting 54·1 ± 5·8% differentiation via αVβ3 and α5β1integrin signalling. Our results demonstrate that plasma protein binding integrins and plasma proteins operate through specific binding domains to induce monocyte-to-DC differentiation in ECP, providing a mechanism that can be harnessed to enhance ECP efficacy.

Extracorporeal photopheresis, a therapeutic option for cutaneous T-cell lymphoma and immunological diseases: state of the art

INTRODUCTION

Extracorporeal photopheresis (ECP) has been extensively used for the treatment of immune-mediated diseases for over 20 years and has a consistent and predictable safety profile with long-term use. Documenting the efficacy of ECP as therapeutic treatment has long been a matter of importance for physicians.

AREAS COVERED

The authors reviewed publications in this field with the goal of providing an overview of this therapeutic approach.

EXPERT OPINION

ECP is efficacious in a high percentage of those cutaneous T-cell lymphoma patients who have circulating malignant T cells in the context of a still-near-normal immune competence. From the side of graft-versus-host disease (GVHD), the use of ECP showed a clinical benefit in patients with steroid-refractory acute GVHD (aGVHD) and it is believed that ECP deserves to be evaluated as part of a combination strategy in first-line therapy of aGVHD. In chronic GHVD, the published data show that ECP can be effective in extensive and long-standing disease even when treatment is initiated at an advanced stage after conventional immunosuppressive and corticosteroid therapy has failed. ECP should be considered most beneficial for patients with predominantly mucocutaneous chronic GVHD. The fields of application of the procedure could be vast, and could also include autoimmune and metabolic diseases. The most important methodological issues which affect ECP evaluation is that the large majority of data about ECP result from single-arm observational series and the significant efficacy is mainly based on small and retrospective studies. ECP has never been proved to offer any survival advantage in a context of a randomized trial and the above-mentioned limitation also affects the accuracy of many biological modifications observed during ECP. Starting from these considerations, the need of a prospective randomized study becomes increasingly urgent.

Extracorporeal photopheresis attenuates murine graft-versus-host disease via bone marrow-derived interleukin-10 and preserves responses to dendritic cell vaccination

Extracorporeal photopheresis (ECP) is emerging as a therapy for graft-versus-host-disease (GVHD), but the full mechanism of action and the impact on immunity have not been fully established. After murine minor histocompatibility antigen-mismatched bone marrow (BM) transplantation (allo-BMT), coinfusion of ECP-treated splenocytes with T cell-replete BM attenuated GVHD irrespective of the donor strain of the ECP-treated splenocytes, and was associated with increased numbers of regulatory T cells. Coculture of myeloid dendritic cells (DCs) with ECP-treated splenocytes resulted in increased interleukin (IL)-10 production after submaximal stimulation with lipopolysaccharide. Furthermore, male myeloid DCs exposed to ECP-treated splenocytes were less potent at inducing CD8(+) HY responses when used as a vaccine in vivo. The efficacy of ECP-treated splenocytes was enhanced when administered just before delayed donor lymphocyte infusion following T cell-depleted allo-BMT, allowing for the administration of sufficient numbers of T cells to respond to myeloid DC vaccination in the absence of a thymus. Finally, the therapeutic effect of ECP-treated splenocytes was lost in recipients of IL-10-deficient BM. We demonstrate that ECP-treated splenocytes attenuate GVHD irrespective of the source of ECP-treated cells via a mechanism that likely involves modulation of DCs and requires IL-10 produced by BM-derived cells. Importantly, the attenuation of GVHD by ECP-treated splenocytes permits donor lymphocyte infusion-dependent responses to DC vaccines after allo-BMT.

The Combination of Immunosuppressive Drugs with 8-Methoxypsoralen and Ultraviolet a Light Modulates the Myeloid-Derived Dendritic Cell Function

The functional properties of myeloid dendritic cells (DCs) differ, depending on microenvironmental factors as well as on their stage of maturation. The main approaches for the selective enhancement of the tolerogenic properties of DCs include the induction of a pharmacological arrest of the DCs maturation and the genetical engineering of DCs expressing immunosuppressive molecules. Several immunosuppressive/anti-inflammatory agents have been discovered that potentially inhibit DC maturation and immunogenicity. Photopheresis (ECP) is an immunomodulatory therapy in which leucocytes are exposed to 8-methoxypsoralen (8-MOP) and ultraviolet (UV) A radiation (PUVA). The combination of ECP with immunosuppressive agents has demonstrated efficacy in the management of transplanted patients by reducing either the incidence of organ rejection or the pharmacological toxicity. In particular, we have observed in hepatitis C virus (HCV)-positive patients that the same combination has reduced the immunosuppressive burden and improved sustainability and efficacy of pre-emptive antiviral therapy after liver transplantation. Therefore, in our work we investigated the in vitro effects of PUVA, combined with immunosuppressive drugs (IDs), on both in vitro human DC generation and maturation, in order to contribute to understanding the immunological mechanisms underlying this pharmacological combination. Monocyte PUVA-treatment was performed by using an in vitro experimental protocol that we previously described. PUVA-treated or -untreated highly purified CD14+ cells were incubated with the association of the immunosuppressive drugs, used in the management of liver transplantation, at two different concentrations, in the presence of IL-4 and GM-CSF. The treatment with IDs at the highest concentration (corresponding to that used in clinical practice), alone or in association with PUVA, induced an immunosuppressive effect, by impairing both DC generation and maturation. Neither immunosuppressive drugs at the lowest concentration nor their combination with PUVA affected myeloid DC generation, but modified DC functions, strengthening the induction of a tolerogenic pattern. As this ID concentration was arbitrarily chosen, further experiments could highlight whether lower concentrations than those used in clinical practice would elicit the same effect on DCs and potentially improve their functional properties. This work describes an original experimental approach exploring the in vitro mechanism of action of the combined procedure of PUVA with immunosuppressive drugs, used in liver transplantation, on DCs generation and function. Our results contribute to the knowledge of the mechanisms of action of this combined procedure on DCs, suggesting useful therapeutic implications for the in vivo therapy.

Apoptotic cell-based therapies against transplant rejection: role of recipient's dendritic cells

One of the ultimate goals in transplantation is to develop novel therapeutic methods for induction of donor-specific tolerance to reduce the side effects caused by the generalized immunosuppression associated to the currently used pharmacologic regimens. Interaction or phagocytosis of cells in early apoptosis exerts potent anti-inflammatory and immunosuppressive effects on antigen (Ag)-presenting cells (APC) like dendritic cells (DC) and macrophages. This observation led to the idea that apoptotic cell-based therapies could be employed to deliver donor-Ag in combination with regulatory signals to recipient’s APC as therapeutic approach to restrain the anti-donor response. This review describes the multiple mechanisms by which apoptotic cells down-modulate the immuno-stimulatory and pro-inflammatory functions of DC and macrophages, and the role of the interaction between apoptotic cells and APC in self-tolerance and in apoptotic cell-based therapies to prevent/treat allograft rejection and graft-versus-host disease in murine experimental systems and in humans. It also explores the role that in vivo-generated apoptotic cells could have in the beneficial effects of extracorporeal photopheresis, donor-specific transfusion, and tolerogenic DC-based therapies in transplantation.

Extracorporeal photopheresis in addition to pentostatin in conditioning for canine hematopoietic cell transplantation: role in engraftment

Extracorporeal photopheresis (ECP) and the purine analog pentostatin exert potent immunomodulatory effects, but have not been evaluated for their ability to enhance engraftment of hematopoietic stem cells. We evaluated, in a canine model of dog leukocyte antigen (DLA)-identical hematopoietic cell transplantation (HCT), whether ECP in combination with pentostatin could enhance engraftment using a nonmyeloablative regimen consisting of 100 cGy TBI and postgrafting immunosuppression with mycophenolate mofetil and CYA. We have shown previously that with 100 cGy TBI alone as conditioning, all of the six dogs rejected their grafts 2-12 weeks after HCT. With the addition of pentostatin to 100 cGy TBI, 6 of 10 dogs rejected their graft. We now tested the additional use of ECP alone (n=2) or ECP and 3-6 doses of pentostatin (n=7) before 100 cGy TBI and HCT. Eight out of nine dogs rejected their grafts within 6-11 weeks after HCT. Compared with data without ECP, we failed to demonstrate a positive impact of the use of either ECP or pentostatin for prevention of rejection.

UV-induced immunosuppressive and anti-inflammatory actions: mechanisms and clinical applications

The introduction in 1974 of psoralens UVA (PUVA) therapy followed in 1987 by extracorporeal photopheresis (ECP) has launched UV light in medicine field. A significant number of potential mechanisms could be linked to the basic cellular UV action (i.e., DNA damage and subsequent cells apoptosis). Phagocytosis by macrophages and dendritic cells (DCs) leads, through a receptor-mediated process, to their modulation. A state of antigen-specific tolerance is induced by induction of Treg cells, inhibition of DCs, which remain at a an immature state, inhibition of production of the proinflammatory cytokines IL-2, IFN-gamma, TNF-alpha and IL-12, and induction of production of cytokines IL-10, TGF-beta and IL-1Ra. Beside cutaneous T-cell lymphoma, use of ECP remains experimental except for graft-versus-host disease, especially the chronic-resistant form. The sparing action of corticosteroids as described in studies on transplantation deserves further attention.

The molecular and clinical rationale of extracorporeal photochemotherapy in autoimmune diseases, malignancies and transplantation

Extracorporeal photochemotherapy, or photopheresis is a low-risk therapeutical intervention, which has been introduced in a variety of hematological malignancies, autoimmune conditions and transplantation. The mode of action of photopheresis encompasses apoptosis-induction and modifications of immunoregulatory processes, leading to the elimination of malignant cells, as well as the down-modulation of harmful immune responses. Although the beneficial effects of the therapy have been depicted in numerous studies, little is known about the exact benefits and the molecular mechanisms behind. The aim of the present review was to portray some aspects of the molecular and clinical rationale of extracorporeal photochemotherapy in autoimmune diseases, malignancies and transplantation, and to provide an overview of the treatment in the modern clinical management of these diseases.

Extracorporeal photopheresis in a rat model of pulmonary fibrosis

Extracorporeal photopheresis has anti-inflammatory properties. The development of pulmonary fibrosis includes inflammatory episodes. This study evaluates effects of extracorporeal photopheresis in experimental pulmonary fibrosis. The bleomycin model of pulmonary fibrosis was used. Two groups of 4 rats received intratracheal bleomycin to induce fibrosis. The treatment group received infusions of photochemically treated leukocytes harvested from syngeneic animals. All animals were sacrificed at day 21 after fibrosis induction and analyzed with respect to lung histology and hydroxyproline content, cellular composition of bronchoalveolar lavages, serum and lavage concentrations of transforming growth factor-beta, interferon-gamma, and interleukin-10, and expression of selected genes in the lung. Interleukin-10 and transforming growth factor-beta protein concentrations increased in the plasma of treated animals, whereas the interferon-gamma protein concentration was higher in bronchoalveolar lavages. Interferon-gamma gene expression was up-regulated in the lung tissue of treated animals. No significant differences between treated and untreated animals were found with respect to hydroxyproline, histology, and lavage cell count. To conclude, extracorporeal photopheresis has positive molecular effects but does not attenuate experimental lung fibrosis with respect to histology, hydroxyproline, and lavage cell count in the applied treatment regimen. Further investigations of extracorporeal photopheresis in experimental pulmonary fibrosis are justified.

Extracorporeal photopheresis-induced immune tolerance: a focus on modulation of antigen-presenting cells and induction of regulatory T cells by apoptotic cells

PURPOSE OF REVIEW

This review is intended to introduce recent advances in the research surrounding extracorporeal photopheresis (ECP) with a focus on how apoptotic cells modulate antigen-presenting cells and induce regulatory T cells, given that ECP therapy induces apoptosis of leukocytes collected through leukapheresis.

RECENT FINDINGS

It has been suggested that ECP therapy, unlike other immunosuppressive regimens, does not cause global immunosuppression, but induces immune tolerance. Recent clinical and animal studies demonstrate that ECP therapy induces antigen-specific regulatory T cells, including CD4+CD25+FoxP3+ T cells and IL-10-producing Tr1 cells, that may arise secondarily to the induction of tolerogenic antigen-presenting cells (APCs) by infusion of apoptotic cells. It has also been suggested that ECP therapy may induce IL-10-producing regulatory B cells and regulatory CD8+ T cells. Finally, several recent studies, which examined the cellular elements involved in the uptake of apoptotic cells, demonstrated that apoptotic cells modulate APCs through binding to specific receptors, particularly TAM receptors that provide inhibitory signals that block APC activation.

SUMMARY

ECP therapy induces immune tolerance through modulation of antigen-presenting cells as well as induction of regulatory T cells. ECP therapy has great potential in the management of allogeneic transplantation and autoimmune diseases.

Extracorporeal photopheresis efficiently impairs the proinflammatory capacity of human 6-sulfo LacNAc dendritic cells

BACKGROUND

Extracorporeal photopheresis (ECP) emerged as a promising treatment modality for steroid-refractory graft-versus-host disease (GVHD), which represents a major complication of allogeneic hematopoietic stem-cell transplantation. Dendritic cells (DCs) display an extraordinary capacity to induce T-cell responses and play a crucial role in the initiation and maintainance of GVHD. This study evaluated the direct impact of ECP on the proinflammatory capacity of 6-sulfo LacNAc (slan) DCs, representing a major subpopulation of human blood DCs.

METHODS

SlanDCs were isolated from ECP-treated or untreated blood of healthy donors or GVHD patients by immunomagnetic isolation. The maturation of slanDC was determined by flow cytometry. Cytokine production of slanDCs was measured by enzyme-linked immunosorbent assay. SlanDC-mediated T-cell proliferation was evaluated by H-thymidine incorporation. SlanDC-mediated T-cell programming was determined by flow cytometry.

RESULTS

ECP efficiently impairs the spontaneous maturation and secretion of proinflammatory tumor necrosis factor-alpha, interleukin-1beta, and interleukin-12 by slanDCs. Furthermore, ECP markedly inhibits slanDC-induced proliferation of CD4 and CD8 T cells and polarization of naïve CD4 T lymphocytes into Th1 cells.

CONCLUSIONS

These novel findings indicate that ECP efficiently impairs the proinflammatory capacity of slanDCs, which may represent an important mechanism for the therapeutic efficiency of ECP in GVHD.

Innovative approaches to treat steroid-resistant or steroid refractory GVHD

First-line treatment of GVHD is based on steroids and produces sustained responses in 50-80% of patients with acute GVHD (aGVHD) and 40-50% of patients with chronic GVHD (cGVHD) depending on the initial disease severity. Non-responding children are offered second-line therapy with combinations of various agents, but currently available agents have not improved survival in these high-risk populations. In this minireview, we will focus on new agents to treat GVHD in paediatric patients.