Inhibition of autoimmune disease in a murine model of systemic lupus erythematosus induced by exposure to syngeneic photoinactivated lymphocytes

CD11c+ dendritic cells mediate antigen-specific suppression in extracorporeal photopheresis

Extracorporeal photopheresis (ECP) represents one of the most widespread and effective cell therapies for graft‐versus‐host disease and other T cell‐mediated disorders. However, the key factors affecting the therapeutic efficacy of ECP remain unclear. We hypothesized that therapeutic effects are mediated by ECP‐treated antigen‐presenting dendritic cells (DC). To test this hypothesis, we used the experimental model of contact hypersensitivity (CHS). The ECP’s therapeutic activity improved when the total cell dose of the ECP‐treated cells was increased. We used different haptens during sensitization to demonstrate that the anti‐inflammatory activity of ECP is antigen‐specific. This confirmed the hypothesis that professional antigen‐presenting cells are involved in the mode of action. Also, the ECP’s therapeutic activity was abrogated by the depletion of CD11c⁺ DC, which represents fewer than 1% of all the ECP‐exposed cells. Finally, we confirm the critical importance of CD11c⁺ DC for ECP activity by showing that only a few purified CD11c⁺ DC are sufficient to mediate its therapeutic effect. The finding that ECP‐treated, physiological antigen‐presenting DC alone mediate antigen‐specific modulation of a pathological immune response may result in better‐targeted interventions when treating patients.

Extracorporeal photopheresis as an immunomodulatory agent: Haematocrit-dependent effects on natural killer cells

The GvHD is a major cause of morbidity and mortality after allogeneic hematopoietic stem cell transplantation (HSCT). Extracorporeal photopheresis (ECP) represents an alternative therapeutic strategy to immunosuppressive therapy. Although ECP is used since 1990s, the mechanism of action has not yet been completely clarified. We analyzed cells collected from 20 ECP procedures of 4 patients affected by chronic GvHD and, for comparison, Peripheral Blood Mononuclear Cells (PBMCs) of 10 healthy donors undergoing from same type of photochemiotherapy, evaluating by flow cytometry, the effects before and after photoactivation with 8-MOP. The analysis showed a significant increase in cell death after ECP in particular in CD4 T lymphocytes as described in literature correlated with haematocrit value. Most interesting data emerge from the analysis of cytotoxic activity of NK cells, using flow cytometry analysis of surface expression of CD107a in the presence of target cells (K562). In all analyzed samples it was possible to document a statistically significant reduction of the cytotoxic activity of NK cells after photoactivation. The decrease of the cytotoxic activity was related to hematocrit value of leukoapheresis: in fact, lower HCT values were associated with a more marked reduction of cytotoxic activity. The study confirms literature data about the increase of cellular mortality induce by ECP. Furthermore, for the first time it is demonstrated that the ECP exerts a marked and significant inhibitory effect on the cytotoxic activity of NK cells. Our study suggests that lower values of hematocrit are associated with better treatment outcome.

A concise review on extracorporeal photochemotherapy: Where we began and where we are now and where are we going!

Currently, more than 1080 peer-reviewed papers are displayed on PubMed when initiating a search for therapeutic indications and mechanisms of action of extracorporeal photochemotherapy (ECP). This concise review focuses mainly on some prevalent and traditional treatment-resistant disorders with an emphasis on immunologic complications emerging from stem cell and solid organ transplantation.

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.

Rapid generation of maturationally synchronized human dendritic cells: contribution to the clinical efficacy of extracorporeal photochemotherapy

Extracorporeal photochemotherapy (ECP) is widely used to treat cutaneous T-cell lymphoma, graft-versus-host disease, and allografted organ rejection. Its clinical and experimental efficacy in cancer immunotherapy and autoreactive disorders suggests a novel mechanism. This study reveals that ECP induces a high percentage of processed monocytes to enter the antigen-presenting dendritic cell (DC) differentiation pathway, within a single day, without added cytokines, as determined by enhanced expression of relevant genes. The resulting DCs are capable of processing and presentation of exogenous and endogenous antigen and are largely maturationally synchronized, as assessed by the level of expression of costimulatory surface molecules. Principal component analysis of the ECP-induced monocyte transcriptome reveals that activation or suppression of more than 1100 genes produces a reproducible distinctive molecular signature, common to ECP-processed monocytes from normal subjects, and those from patients. Because ECP induces normal monocytes to enter the DC differentiation pathway, this phenomenon is independent of disease state. The efficiency with which ECP stimulates new functional DCs supports the possibility that these cells participate prominently in the clinical successes of the treatment. Appropriately modified by future advances, ECP may potentially offer a general source of therapeutic DCs.

Selective immmunotherapy through extracorporeal photochemotherapy: yesterday, today, and tomorrow

ECP's extensive clinical record, as well as a considerable improvement in the understanding of the mechanism that underlies its efficacy, opens potential novel strategies for the treatment of cancer, GVHD, transplant rejection, and autoimmunity. The low side effect profile of this therapy has made it a more attractive treatment consideration than current conventional chemotherapeutic and immunosuppressive medications. As the mechanism of action of ECP is more fully elucidated and clinical studies are completed, the role of ECP in modern therapeutics of CTCL and other malignancies, as well as in the treatment of other T-cell mediated diseases, will be become clearer.

Mechanisms of action of extracorporeal photochemotherapy

Extracorporeal photochemotherapy (ECP) has been shown to be effective in variety of pathologic diseases such as Sezary syndrome, autoimmune diseases, organ graft rejection and graft versus host disease. However, its mechanism of action has remained elusive. Understanding of its mechanisms may be useful to identify the best indications, treatment regimes and to optimize the ECP technique. The first step of the ECP procedure is collection of peripheral mononuclear cells. In this step, several cell environment changes occur. These conditions have been suggested to increase monocyte activation and possibly drive dendritic cell differentiation. The second step of ECP is the cell radiation by UVA in presence of 8-MOP which is presumed to induce cell membrane damage, DNA crosslinking and binding to a variety of cytosolic proteins leading to apoptosis, modification of membrane antigenicity and antigen presenting cell activation. The third step of ECP is the reinfusion of the treated cells to the patient. While it is unclear what exactly occurs in vivo, it is thought that DCs play a critical role by inducing an immunological response against pathogenic cells. The immature DC, activated by ECP, phagocytizes and internalizes the apoptotic cells; processes the antigens and increases the synthesis of class I and II Major Histocompatibility Complex (MHC) molecules. The peptides associated with class II MHC are presented to the CD4+ T helper cells. The final maturation of DC is completed in vivo with the help of these activated T helper cells using a variety of mechanisms including CD40 ligation. Finally, the mature DCs fully loaded with pathogenic T cell peptides migrate to secondary lymphoid organs stimulate the naive CD8+ T cells and induce a cytotoxic response (Th1 immune response) directed against pathogenic clones (tumoral cells of Sezary syndrome). Clinical and haematological improvement after ECP in Sezary syndrome is associated with a shift in Th1/Th2 balance and the increase of Th1 cytokines and IL12. ECP can also down regulate the allo or autoimmune response and induces tolerance by regulatory T cells. The clinical response to ECP in patients with chronic GvHD is associated with increase in NK cells and a shift from DC1 to DC2 and a shift from predominantly Th1 to Th2 immune response. Recruitment and involvement of other immune cells in the mechanism of ECP have been suggested and merit more studies. This immunostimulatory capacity of ECP is the most probable hypothesis of its mechanism but further investigations are necessary to determine the precise players important for this activity.

Extracorporeal photochemotherapy for paediatric patients with graft-versus-host disease after haematopoietic stem cell transplantation

This study aimed to ascertain whether extracorporeal photochemotherapy (ECP) is an effective treatment for paediatric patients with refractory graft-versus-host disease (GVHD). From January 1992 to December 2000, 77 children (median age 8.6 years) with either acute (n = 33) or chronic (n = 44) GVHD, resistant to conventional immunosuppressive therapy, were treated with ECP in four Italian paediatric hospitals. After ECP, acute GVHD involving skin, liver and gut responded completely in 76%, 60% and 75% of patients respectively. The 5-year overall survival was 69% for responding patients vs 12% for non-responders (P = 0.001). Among the 44 children with chronic GVHD, 15 (44%) showed a complete response and 10 (29%) a significant improvement after ECP. The 5-year overall survival was 96% for responders vs 58% for non-responders (P = 0.04). Our results suggest that ECP is an effective treatment that may be useful in paediatric patients with either acute or chronic GVHD who have failed to respond to standard immunosuppressive therapy.

Extracorporeal photochemoimmunotherapy in cutaneous T-cell lymphoma

Extracorporeal photochemotherapy was originally conceived for the treatment of cutaneous T-cell lymphoma (CTCL) and as well as other T-cell mediated diseases. Evidence collected in the past 17 years has demonstrated that this treatment modality can have a very significant effect on the course of a subset of CTCL patients. The evidence available is positive but for a variety of reasons has been controversial within the medical community. A number of very well-designed multi-center trials which have been lacking since the first publication by Edelson et al. are being carried out so that hopefully a number of open questions will be resolved with greater clarity in the coming years. The fact remains that this innovative approach for the treatment of CTCL and T-cell mediated diseases has certainly opened new avenues of therapy and thought in photoimmunology and photomedicine. Clearly the very low side effect profile of this therapy has made it more attractive than the chemotherapeutic and immunosuppressive substances that are presently available or in experimental protocols. If and when the mechanisms of action are fully understood and appropriate studies investigating different treatment schedules and different combination therapies and modifications of its present form are performed the place of photopheresis in the therapeutics of CTCL as well as other T-cell mediated diseases and oncology will be better placed.

Identification of amplified clonal T cell populations in the blood of patients with chronic graft-versus-host disease: positive correlation with response to photopheresis

Chronic graft-versus-host disease (cGVHD) is a multiorgan disorder with skin manifestations resembling scleroderma. Since photopheresis, a treatment that induces an anticlonotypic immune response, has proven to be effective in both cutaneous T cell lymphomas with circulating clonal T cells and in cGVHD, we have searched for circulating clonal T cell populations in patients with cGVHD, and determined whether T cell clonality in the blood is associated with therapeutic response. We screened blood samples from 27 patients after HLA-matched allogeneic bone marrow transplantation (allo-BMT), 10 without cGVHD and 17 with extensive cGVHD, for clonal T cell receptor gamma (TCR gamma) gene rearrangements using fluorescent-based polymerase chain reaction (PCR) and automated high-resolution capillary electrophoresis. Amplified populations of clonal T cells with unique TCR gamma gene rearrangements were found in six of 10 (60%) allo-BMT patients without cGVHD and 13 of 17 (76.5%) allo-BMT patients with cGVHD (P = 0.41), as compared to none of 10 (0%) healthy controls. Twelve patients with cGVHD were treated by photopheresis, and the presence of amplified populations of clonal T cells was found to be associated with a cutaneous response to photopheresis, as eight of eight (100%) clone-positive vs none of four (0%) clone-negative patients experienced a clinically significant cutaneous response to treatment (P = 0.001). Our findings suggest that patients with cGVHD that have detectable expanded clonal T cell populations in their peripheral blood, may be more likely to respond to treatment by photopheresis.

Extracorporeal photochemotherapy for the treatment of graft-versus-host disease

Photopheresis (extracorporeal photochemotherapy, ECP) is a new type of photochemotherapy used for the treatment of oncological and autoimmune diseases. Additionally, recent reports indicate that this therapy is promising in both pediatric and adult patients who develop graft versus host disease (GVHD) resistant to conventional protocols after bone marrow transplantation (BMT). In this paper, we review 31 studies where ECP was used in the treatment of acute and chronic GVHD. A total of 76 (32% female) acute GVHD patients have been considered in 11 series. Fifty-nine patients presented with skin involvement; 47 had liver involvement, and 28 had gastrointestinal manifestations. Treatment duration ranged from 1 to 24 months. A regression of skin manifestations was observed in 83% of the patients with a complete response in 67%. A complete regression of liver and gut manifestations was reported in 38% and 54% of the patients, respectively. The overall patient survival was 53%. Of the 43 patients alive, 8 developed chronic GVHD manifestations. The immunosuppressive therapy was discontinued in 28% of cases and reduced in 46%. A total of 204 (45% female) chronic GVHD patients treated with ECP 1 to 110 months from transplantation have been considered in 20 series. One hundred twenty-eight patients presented with skin involvement, 84 with liver, 31 with lung, and 59 with oral manifestations. Treatment duration ranged from 3 to 40 months. A regression of skin manifestations was observed in 76% of patients with a complete response in 38%. An improvement of liver and lung involvement was reported in 48% and 39% of the patients, respectively. Of the 59 patients with oral manifestations, an improvement was obtained in 63% of cases. The overall patient survival was 79%. ECP is a nonaggressive treatment that may benefit patients with both acute and chronic GVHD who do not respond to standard immunosuppressive therapy.

T cell clonality and the effect of photopheresis in systemic sclerosis and graft versus host disease

Photopheresis, a leukapheresis-based therapy that combines 8-methoxypsoralen (8-MOP) and ultraviolet-A irradiation, has been shown to be an effective treatment for advanced cutaneous T cell lymphoma (CTCL), but also appears to be effective in certain patients with systemic sclerosis (SSc) and chronic graft versus host disease (cGVHD). In CTCL, clinical responsiveness to photopheresis has been shown to be dependent on the presence of detectable circulating clonal T cells in peripheral blood. Herein we review recent work from our group demonstrating that circulating clonal populations of T cells are detectable in a subgroup of patients with SSc and cGVHD. Furthermore, we provide initial evidence that the presence of a T cell clone in such patients may be associated with responsiveness to photopheresis.

Transimmunization and the evolution of extracorporeal photochemotherapy

We are now aware that extracorporeal photopheresis (ECP) - in which a patient's leukocytes are isolated, passed through an ultrathin clear plastic plate, and exposed to 8-methoxypsoralen (8-MOP) and ultraviolet A light prior to reinfusion - is a simple and efficient dendritic cell (DC) therapy and the first FDA approved selective immunotherapy for cancer. DCs, as the most effective antigen presenting cells (APCs), are central to many ongoing efforts to stimulate immune responses to cancer cells. Moreover, ECP has not only demonstrated efficacy in the treatment of a T cell malignancy--namely cutaneous T-cell lymphoma (CTCL)--but also in treatment of oligoclonal T-cell-mediated diseases such as graft-versus-host-disease (GVHD) and organ transplant rejection. Recent advances in the understanding of DC/T-cell interactions provide insight into how ECP-induced DCs (EI-DCs) can be utilized to stimulate specific T-cell (i.e. anti-tumor) responses, or down-regulate a pre-existing potent T-cell response. The mechanism of this apparent paradox of EI-DC functionality is likely dependent on several fundamental principles: (1) the status of existing in vivo T-cell reactions, (2) the temporal stage of EI-DC differentiation, and (3) the affinity of the available repertoire of T-cell receptors (TCRs) for the antigen(s) in question. Further investigation into DC/T-cell interactions will help to shape the future of ECP and the ability to optimize this therapy for the desired immune effect. To this end, we are developing and testing Transimmunization to replace conventional ECP.

Transimmunization, a novel approach for tumor immunotherapy

This review describes our experience with the development of a novel form of immunotherapy that may represent the first practical and effective means of performing tumor-loaded dendritic cell (DC) immunotherapy. We have modified the highly successful extracorporeal photopheresis (ECP) treatment that has been used in the therapy of cutaneous T cell lymphoma (CTCL). autoimmune disease, transplantation rejection episodes and graft-versus-host disease to enhance its efficacy by the addition of an overnight incubation period. This adaption of ECP is termed "transimmunization (TI)" since the new therapy permits transfer of tumor antigens that have been previously poorly recognized to potent antigen presenting cells where the tumor epitopes can be displayed in the full context of major histocompatibility, co-stimulatory and adhesion molecules. The TI modification of ECP is a practical and safe means of rapidly inducing DC differentiation from peripheral blood monocytes in the presence of apoptotic tumor cells. Uptake of the apoptotic CTCL cells by the immature DC, in the presence of inflammatory cytokines, further drives their maturation into potent antigen presenting cells. Reinfusion of these tumor-loaded DC, that have access to the full spectrum of tumor antigens, has the potential to invoke an anti-tumor immune response in the recipient. Standard ECP has been a very useful form of immunotherapy and a modification of this approach that can enhance its ellicacy and utility should broaden its application to a larger variety of disorders including potentially the treatment of solid tumors and the modulation of the immune response in graft-versus-leukemia and graft-versus-host transplantation regimens. An understanding of the mechanism of ECP and TI will provide the physician with the ability to more finely tune the desired immune response and thereby, provide an enhanced immunotherapy for malignancy and other disorders of immunocompetence.

Extracorporeal photochemoimmunotherapy in cutaneous T cell lymphomas

Extracorporeal photochemotherapy (ECP), or photopheresis, is a widely used treatment for cutaneous T cell lymphoma (CTCL) and other T cell-mediated disorders, having been administered in more than 150 centers worldwide more than 200,000 times. Consistent with the theme of this conference--that is, highlighting the potentially most productive investigative avenues for unraveling the mysteries of CTCL in the next decade--ECP has been futuristic since its inception in the early 1980s. In 1988, the treatment was the first FDA-approved selective immunotherapy for any type of cancer. Yet, the mechanism by which it could suppress a clone of CTCL cells or inactivate multiple autoreactive T cell clones in graft-versus-host disease (GVHD) or allograft rejection remained obscure until quite recently. In fact, the scientific principles necessary to begin to comprehend the basis of ECP's efficacy were not available when the treatment was first introduced in 1982. In the intervening years, necessary detailed knowledge of the structure and function of the clonotypic T cell receptors, of class I major histocompatibility complex (MHC) presentation of tumor antigens, of CTCL tumor-specific antigens, of dendritic antigen presenting cell (DC) biology, and of 8-methoxypsoralen immunopharmacology has been attained. Although much remains to be learned, we now appreciate that ECP simultaneously and efficiently induces both apoptosis of disease-causing T cells and conversion of monocytes to functional DCs. By processing and presenting the unique antigenic determinants of pathogenic T cell clones, the DCs can either initiate a clinically relevant anti-CTCL cytotoxic response or suppress the activity of autoreactive T cell clones. This paper will review clinical trials of ECP in CTCL and evolving scientific understanding of ECP's mechanism in the context of exciting future directions.

Extracorporeal photochemotherapy in patients with steroid-dependent Crohn's disease: a prospective pilot study

BACKGROUND

Extracorporeal photochemotherapy has been proven effective in selected T-cell mediated diseases.

AIM

To evaluate the safety and efficacy of extracorporeal photochemotherapy in patients with steroid-dependent Crohn's disease by an open, monocentric trial in three phases of 24 weeks each.

METHODS

In phase 1 standardized steroid tapering was initiated in patients with a history of steroid-dependent Crohn's disease. Those with a prospectively evaluated maintenance dose of at least 10 mg/day prednisolone continued steroid-withdrawal under the application of extracorporeal photochemotherapy in phase 2. The duration of remission or response was followed during phase 3. Colonic tissue bioptically obtained before and after extracorporeal photochemotherapy was studied by immunofluorescence microscopy for the presence of photoadduct positive cells.

RESULTS

Out of 24 patients included in phase 1, 10 entered phase 2 for extracorporeal photochemotherapy. Four subjects achieved remission and four others response. Significant reductions in serum C-reactive protein levels and intestinal permeability were measured, as well as increases in quality of life and plasma adrenocorticotropic hormone levels. No major side-effects were observed. Remission remained stable in three out of four patients during phase 3. In three patients, positive nuclear stainings of photoadducts were detected in colonic mononuclear cells after extracorporeal photochemotherapy.

CONCLUSIONS

Extracorporeal photochemotherapy represents a safe steroid-sparing approach in patients with Crohn's disease and is associated with intestinal homing of photopheresed cells.

Photopheresis at onset of type 1 diabetes: a randomised, double blind, placebo controlled trial

BACKGROUND

In recent years photopheresis, an extracorporeal form of photochemotherapy using psoralen and ultraviolet A irradiation of leucocytes, has been claimed to be an effective form of immunomodulation.

AIM

To evaluate its effect in type 1 diabetes we performed a double blind, controlled study using placebo tablets and sham pheresis in the control group.

METHODS

A total of 49 children, aged 10-18 years of age at diagnosis of type 1 diabetes were included; 40 fulfilled the study and were followed for three years (19 received active treatment with photopheresis and 21 placebo treatment).

RESULTS

The actively treated children secreted significantly more C peptide in urine during follow up than control children. C peptide values in serum showed corresponding differences between the two groups. The insulin dose/kg body weight needed to achieve satisfactory HbA1c values was always lower in the photopheresis group; there was no difference between the groups regarding HbA1c values during follow up. The treatment was well accepted except for nausea (n = 3) and urticaria (n = 1) in the actively treated group. There were no differences regarding weight or height, or episodes of infection between the two groups during follow up.

CONCLUSION

Photopheresis does have an effect in addition to its possible placebo effect, shown as a weak but significant effect on the disease process at the onset of type 1 diabetes, an effect still noted after three years of follow up.

Extracorporeal photochemotherapy in the treatment of severe steroid-refractory acute graft-versus-host disease: a pilot study

Extracorporeal exposure of peripheral blood mononuclear cells to the photosensitizing agent 8-methoxypsoralen and UV-A radiation has been shown to be effective in the treatment of selected diseases mediated by T cells, rejection after solid organ transplantation, and chronic graft-versus-host disease (GVHD). We present 21 patients with a median age of 38 years who developed steroid-refractory acute GVHD grades II to IV after stem cell grafting from sibling or unrelated donors and were referred to extracorporeal photochemotherapy (ECP). Three months after initiation of ECP 60% of patients achieved a complete resolution of GVHD manifestations. Complete responses were obtained in 100% of patients with grade II, 67% of patients with grade III, and 12% of patients with grade IV acute GVHD. Three months after start of ECP complete responses were achieved in 60% of patients with cutaneous, 67% with liver, and none with gut involvement. Adverse events observed during ECP included a decrease in peripheral blood cell counts in the early phase after stem cell transplantation (SCT). Currently, 57% of patients are alive at a median observation time of 25 months after SCT. Probability of survival at 4 years after SCT is 91% in patients with complete response to ECP compared to 11% in patients not responding completely. Our findings suggest that ECP is an effective adjunct therapy for acute steroid-refractory GVHD with cutaneous and liver involvement. However, in patients with acute GVHD grade IV or gut involvement other therapeutic options are warranted.

Extracorporeal photochemotherapy in the treatment of severe steroid-refractory acute graft-versus-host disease: a pilot study

Extracorporeal exposure of peripheral blood mononuclear cells to the photosensitizing agent 8-methoxypsoralen and UV-A radiation has been shown to be effective in the treatment of selected diseases mediated by T cells, rejection after solid organ transplantation, and chronic graft-versus-host disease (GVHD). We present 21 patients with a median age of 38 years who developed steroid-refractory acute GVHD grades II to IV after stem cell grafting from sibling or unrelated donors and were referred to extracorporeal photochemotherapy (ECP). Three months after initiation of ECP 60% of patients achieved a complete resolution of GVHD manifestations. Complete responses were obtained in 100% of patients with grade II, 67% of patients with grade III, and 12% of patients with grade IV acute GVHD. Three months after start of ECP complete responses were achieved in 60% of patients with cutaneous, 67% with liver, and none with gut involvement. Adverse events observed during ECP included a decrease in peripheral blood cell counts in the early phase after stem cell transplantation (SCT). Currently, 57% of patients are alive at a median observation time of 25 months after SCT. Probability of survival at 4 years after SCT is 91% in patients with complete response to ECP compared to 11% in patients not responding completely. Our findings suggest that ECP is an effective adjunct therapy for acute steroid-refractory GVHD with cutaneous and liver involvement. However, in patients with acute GVHD grade IV or gut involvement other therapeutic options are warranted.

Prophylactic photopheresis and chronic rejection: effects on graft intimal hyperplasia in cardiac transplantation

BACKGROUND

Despite the decreased incidence of acute rejection episodes and improvements in short and intermediate term graft survival with current immunosuppressive agents, there has been little progress in decreasing the morbidity and mortality from chronic rejection. This phenomenon may, in part, be related to the development of a humoral immune response with increases in anti-HLA antibodies, which presents as accelerated graft arteriopathy with intimal hyperplasia.

METHODS

Based on prior experimental work, a pilot, prospective, randomized study was performed in 23 primary cardiac transplant recipients to determine whether the addition of prophylactic photopheresis to a cyclosporine, azathioprine and prednisone regimen was safe and resulted in decreased levels of panel reactive antibodies (PRA) and transplant arteriopathy.

RESULTS

There was no difference between the two groups in regard to infection or acute rejection incidence. The photopheresis group had a significant reduction in PRA levels at two time points within the first 6 postoperative months. Coronary artery intimal thickness was significantly reduced in the photopheresis group at 1-yr (0.23 vs. 0.49 mm, p < 0.04) and 2-yr (0.28 vs. 0.46 mm, p < 0.02) follow-up compared with the control group.

CONCLUSION

In this small pilot study, photopheresis is a safe, well-tolerated immunomodulatory technique that is capable of decreasing the severity of chronic rejection manifesting as post-transplant graft intimal hyperplasia.

Photochemical Treatment with S-59 Psoralen and Ultraviolet A Light to Control the Fate of Naive or Primed T Lymphocytes In Vivo After Allogeneic Bone Marrow Transplantation

Donor leukocyte infusions after allogeneic bone marrow transplantation can provide a curative graft-vs-leukemia (GVL) effect, but there is a significant risk of graft-vs-host (GVH) disease. A simple and effective method for controlling the fate of naive or primed T-lymphocytes in vivo without eliminating their beneficial properties is needed. In this report, photochemical treatment (PCT) ex vivo with a synthetic psoralen (S-59) and UVA light was evaluated as a pharmacological approach to limiting the proliferation and GVH potential of naive and primed donor T cells in vivo. S-59 rapidly intercalates into and cross-links DNA on UVA illumination. The effects of PCT on T cells were found to be both S-59 and UVA dose dependent. With selected PCT regimens, treated T cells still expressed activation markers (CD25 and CD69) and secreted IL-2 on activation, but they showed limited proliferative capacity in vitro and in vivo. Clonal expansion of CTL in MLR was reduced after PCT, but short term lytic activity of primed CTL was not affected. In a murine model of MHC-mismatched bone marrow transplantation, the addition of PCT-treated T cells to T-depleted bone marrow facilitated donor engraftment and complete chimerism without causing acute or chronic graft-vs-host disease. Allospecific GVL reactivity was reduced but not eliminated after PCT treatment. In an MHC-matched model using host-presensitized donor T cells, PCT significantly reduced GVH-associated mortality without eliminating GVL reactivity. Thus, PCT ex vivo offers a simple, rapid, and inexpensive method by which to control the fate of naive and primed T cells in vivo.

Long-term application of extracorporeal photochemotherapy in severe atopic dermatitis

BACKGROUND

Extracorporeal photochemotherapy (ECP) using UVA irradiation of enriched leukocytes in the presence of methoxsalen as a photoactivatable substrate has been employed for the treatment of several immunologically mediated disorders.

OBJECTIVE

Our purpose was to determine the efficacy and safety of long-term ECP in the treatment of severe atopic dermatitis.

METHODS

Fourteen patients with severe recalcitrant atopic dermatitis were treated with ECP in an open clinical trial at 2-week intervals. Disease activity was scored before each ECP cycle by means of a standardized protocol.

RESULTS

A complete clinical remission was achieved in 4 patients (29%). Five patients (36%) experienced a substantial response with reduction of skin inflammation by at least 75%, whereas in one patient (7%) disease activity was reduced by more than 50%. Four patients were withdrawn from the study for unresponsiveness. No clinical signs of immunosuppression or other severe adverse events became evident.

CONCLUSION

Long-term ECP may have significant beneficial effects on the course of atopic dermatitis and should therefore be considered as a treatment modality for patients suffering from severe and otherwise refractory atopic skin disease.

Photoactivated 8-methoxypsoralen treatment causes a peptide-dependent increase in antigen display by transformed lymphocytes

Ex vivo exposure of malignant human T cells to photoactivated 8-methoxypsoralen (8-MOPa), followed by their i.v. return, appears to vaccinate patients against tumor-associated antigens of cutaneous T cell lymphoma in a procedure termed photopheresis. The molecular basis of this Food and Drug Administration-approved therapy, administered in 100 centers worldwide, is unclear. Most of the attention to the mechanism of action of the drug has focused on its capacity to form covalent cross-links with pyrimidine bases of DNA, thereby inhibiting cellular proliferation. Because immunologic factors appear to be important in the clinical response and could potentially serve as a model for immunotherapy of other malignancies, we explored the possibility that 8-MOP-treated cells display increased quantities of antigenic peptides at their cell surface. In this work, human B-lymphoblastoid tissue culture lines were exposed to 8-MOPa and expression of cell surface class I major histocompatibility complex proteins assessed, since CD8 T cells recognize antigenic moieties in the context of class I molecules. A peak 200-300% increase in MHC class I expression in 8-MOPa-treated cells occurred at 20 hr. 8-MOPa was far more effective in inducing this increase in class I MHC than other modalities, including mitomycin C, gamma-irradiation, ultraviolet B or heat or cold shock. This increase in surface class I MHC molecules appears to be driven by the degradation of cytoplasmic proteins into small peptides, followed by the transport of these peptides to MHC class I molecules in the endoplasmic reticulum. The data suggest that 8-MOPa treatment may augment the immunogenicity of tumor and/or antigen-presenting cells by enhancing processing and transport of class I MHC antigenic peptides.

Clinical and mechanistic aspects of photopheresis

Photopheresis is an extracorporeal form of photochemotherapy with 8-methoxypsoralen (8-MOP) and ultraviolet A (UVA) radiation. Photopheresis is used for the management of T-cell-mediated diseases, and such treatment leads to the induction of antigen-specific immune suppression directed to the pathogenic clone of T cells. Photopheresis is used to treat a wide variety of diseases--such as cutaneous T-cell lymphoma, systemic sclerosis; rheumatoid arthritis, lupus erythematosus--and is also successfully applied in the suppression of graft rejection. In addition to the clinical achievements, attention will be paid to results from animal studies. An important outcome of these studies is that photopheresis can be used to treat airway hyperreactivity. Furthermore, it was shown that the therapeutic strategy can be changed drastically: the presence of plasma during irradiation should be avoided and the amount of blood that must be treated to obtain the desired antigen-specific immunosuppression can be greatly decreased. Also, results from cellular experiments are discussed. An example of this is the increase in the major histocompatibility complex expression on the surface of cells found after treatment. The mechanism that underlies photopheresis has not yet been elucidated, but progress has been made. The following related points will be reviewed: models for investigation; and mechanistic aspects, with the emphasis on cellular biomacromolecules and on photosensitizers (drugs) other than 8-MOP.

Singlet oxygen producing photosensitizers in photophoresis

In this study, the immunosuppressive properties of two photosensitizers (benzoporphyrin derivative monoacid ring A (BPD) and Photofrin (HPD)), used for the photodynamic therapy of cancer, were investigated. The investigations were performed in our rat model for photophoresis. The validity of this model has been amply demonstrated. It enables a distinction to be made between antigen-specific and antigen non-specific immune suppression. With this model, the immune response which can be specifically suppressed is the contact hypersensitivity (CHS). CHS is induced by 2,4-dinitrofluorobenzene (DNFB). Both BPD and HPD are able to suppress CHS induced by DNFB. Furthermore, this generated suppression is transferable by the spleen cells of treated animals and is antigen non-specific.

Photopheresis, a possible therapy for airway hyperreactivity?

Airway hyperreactivity is an almost universal feature of asthma. The exact origin of this phenomenon is poorly understood. However, there is increasing evidence that T cells play an important role in the pathogenesis of this disorder. This fact makes it challenging to photopheresis to suppress the pulmonar hyperreactivity response. Photopheresis is a therapy for T cell mediated diseases aiming at specific suppression of the pathogenic clone of T cells involved. The use of photopheresis for the treatment of airway hyperreactivity was investigated in this study. We performed experiments in a murine model for airway hyperreactivity. In short, mice were sensitized by cutaneous application of 2,4,6-trinitrochlorobenzene. The immune system was challenged by an intratracheal injection of 2,4,6-trinitrobenzenesulfonic acid and a bronchoalveolar lavage was performed. In this lavage the total number of leukocytes was established and the number of macrophages was determined. It was found that photopheresis treatment was capable to suppress the airway hyperreactivity response for about 80%. In addition, the generated suppression proved to be transferable by splenocytes of treated animals. We conclude that photopheresis can be an interesting therapy for airway hyperreactivity (and perhaps also for asthma) especially when one takes into account that photopheresis induces specific immune suppression and has hardly any adverse effects.

The immunological effect of 8-methoxypsoralen and UVA treatment on murine T-cell leukemia

8-Methoxypsoralen (8-MOP) plus long-wavelength UV radiation (UVA, 320-400 nm) have been used to treat various diseases such as cutaneous T-cell lymphoma, systemic scleroderma, rheumatoid arthritis and rejection of heart transplants. However, the immunological mechanism of this treatment remains unknown. In this report, we investigated the effect of 8-MOP/UVA on the modulation of the immunogenicity of a T-cell leukemia cell line (RL male 1 cells). The results demonstrated that the stimulator function of the in vitro 8-MOP/UVA-treated RL male 1 cells was enhanced in both RL male 1-specific allogeneic and syngeneic immune responses. Furthermore, the enhancement of the immunogenicity of the 8-MOP/UVA-treated RL male 1 cells was found to be strongly associated with the increase of intercellular adhesion molecule-1 expression on these 8-MOP/UVA-treated tumor cells. Therefore, our findings suggested that the alteration of the expression of the immune-related cell surface molecules might be an important effect of 8-MOP/UVA treatment on the elevation of the immunogenicity of the 8-MOP/UVA-treated tumor cells.

Immunomodulation in transplantation with photopheresis

Photopheresis is a technique in which peripheral blood mononuclear cells, in the presence of a photoactivatable compound, are exposed extracorporeally to ultraviolet A light and reinfused, inducing a host autoregulatory immune response. Experimental work and ongoing clinical studies are helping to define the role of this novel, safe, and non-toxic immunomodulating technology in the field of transplantation.

Chlorpromazine, a candidate drug for photopheresis

Photopheresis is a therapy for several T-cell-mediated disorders, aiming at a specific immune response against the pathogenic clone of T cells involved. With photopheresis, a mixture of patients' buffy coat and plasma, which contains 8-methoxypsoralen (8-MOP), is diluted with saline and exposed to ultraviolet A radiation (UVA). After the irradiation the treated fraction is reinfused. To improve this therapy and to broaden its scope, insight into the underlying mechanism is essential. Regarding the mechanism, photomodification of biomacromolecules is considered to be crucial in photopheresis. Up to the present, much emphasis has been put on the photobinding to DNA. However, photobinding to proteins can also play an important role in photopheresis, because much of the communication between the various parts of the immune system occurs via protein-protein interactions. In this study we compared the activity of 8-MOP and chlorpromazine (CPZ) in our animal model for photopheresis based on contact hypersensitivity. It proved that CPZ was able to induce specific immune suppression, just as 8-MOP. In addition, photobinding of CPZ and 8-MOP to lymphocytes was determined. It was shown that under conditions relevant for photopheresis the photobinding to DNA of 8-MOP exceeds that of CPZ by a factor of 22. This holds for both rat and human lymphocytes. With the photobinding to proteins it is just the other way round; the photobinding of CPZ exceeded that of 8-MOP by a factor of 23 for rat lymphocytes and 28 for human lymphocytes. This study proves that CPZ is an interesting candidate drug for photopheresis and shows that not only photobinding to DNA is crucial in photopheresis, but photobinding to proteins is important as well.

Cytolytic response to HIV in patients with HIV disease treated with extracorporeal photochemotherapy: preliminary study

Extracorporeal photochemotherapy (photopheresis), an immunomodulatory therapy that targets circulating T helper lymphocytes, has been applied to the management of human immunodeficiency virus (HIV) disease. Any therapy that exerts its actions on CD4+ T cells has the potential of exacerbating HIV infection. Therefore, it was necessary to observe immune function during treatment. Because cytotoxic T lymphocytes (CTL) and natural-killer cells are thought to play an important role in the response against HIV infection, we examined the effect of photopheresis on HIV cytolytic activity. The study group consisted of seven patients with late-stage HIV disease who had not received any previous treatment for HIV infection. Patients were treated exclusively with photopheresis on two consecutive days each month for 14-32 months (average, 25 months). Peripheral lymphocytes, collected at various points during treatment, were used as effectors in a 51Cr release assay. Epstein-Barr virus (EBV)-transformed autologous B cell lines transfected with recombinant vaccinia vectors that expressed the HIV env (gp120, gp41) and gag (p24) proteins were used as target cells. All seven patients demonstrated relatively constant levels of cytolysis (>10% above controls) during treatment in the context of stable CD4+ T cell counts and a stable clinical status. These results suggest that extracorporeal photochemotherapy did not impair the cytolytic response to HIV infection and may have enhanced it in some patients.

Psoralen photobiology: recent advances

Clinical efficacy may arise from psoralen-induced photodamage by the induction of a panoply of biomolecules. In cellular studies with UV or photoactivatable agents, the activation of NF-kappa B, probably the most widely studied transcription factor, occurs after its release from an inhibiting factor, I kappa B. The activation of transcription factors has also been correlated with the UV absorption spectrum of DNA (35). Furthermore, it was shown that the photoadducts do not need to be processed or repaired because transcription factor induction is observed in repair-deficient cells. In these latter cells lower UV doses are required to induce these transcription factors. As a result of transcription factor induction, treated cells may have a greater number of class I molecules on their surface and an altered cytokine profile. It is possible (and likely) that these effects occur in different cells to different extents. The important message is that activational events may occur that could alter the cell's (or cells') ability to regulate a disease process. Many studies have shown that the time frame for this type of damage-induced event may range from seconds to minutes (36). Clearly 8-MOP/UVA-induced events such as those described above could be initiated as the result of a single photochemotherapy session.

Increased surface expression of class I MHC molecules on immunogenic cells derived from the xenogenization of P815 mastocytoma cells with 8-methoxypsoralen and long-wavelength ultraviolet radiation

In a previous study we demonstrated that the treatment of the highly tumorigenic cell line, P815, with 8-methoxypsoralen and long-wavelength ultraviolet radiation resulted in the production of several immunogenic clones (tum-). Mice inoculated with the tum- cells survived much longer than mice inoculated with the original tumorigenic cells (tum+). It was suggested that the increased survival of mice treated with the tum- clones arose as a result of an increased antigenicity derived from the phototreatment. In this report we show that the tum- cells have a greater density of class I MHC molecules on their surface (50-157% compared to P815). Class I MHC density on the cell surface is required to elicit targeted cytotoxic responses. These results can be considered in terms of human class I MHC assays which show that many human tumor cells have a reduced expression of class I MHC. Because other DNA damaging agents have also been shown to enhance class I expression, it is suggested that in addition to the cytotoxic effects of these agents, other pleiotropic effects must be considered. Photochemotherapy may phenotypically alter cells so that the enhanced expression of class I MHC molecules on the surface of phototreated cells may be associated with the clinical responses observed in cutaneous T cell lymphoma patients.

Non-specific systemic immune suppression induced by photodynamic treatment of lymph node cells with bacteriochlorin a

Although photodynamic therapy is being used increasingly for the treatment of cancer, its effect on immune responses has received little attention. This aspect was studied in a rat model. Rats were given (intravenously) lymph node cells which were simultaneously exposed to a photosensitizer and light. As a result of this treatment the animals showed a decreased contact hypersensitivity response. Most important is that the generated immunosuppression proved to be non-specific. The consequence of this finding may be that photodynamic therapy of tumours can inhibit the immune response against malignant cells.

Targeting of phototoxic drugs to antigen-specific T lymphocytes in vitro using antigen-presenting cell membranes

We have used the complex of antigen with class II major histocompatibility proteins (Ia) in membrane-bound form to target a phototoxic compound to antigen-specific T cell hybridomas in vitro. The iodoacetamidyl ester of phototoxic pyrene was bound covalently to antigen-presenting cells (APC), and protein antigens were added to the cells for processing, presentation and targeting of the drug to three different T hybridomas specific for myelin basic protein (MBP), ovalbumin (OVA) and keyhole limpet hemocyanin (KLH). The B hybridoma LS102.9 was used as APC to present MBP, KLH and either a tryptic digest of OVA or the synthetic peptide OVA323-339 to these T cells. A transformed B lymphoma, which expresses trinitrophenol (TNP)-specific surface IgM, A20-HL, was used to present TNP conjugates of KLH and OVA to T cells. Either the antigen-bearing intact APC or Ia+ membranes shed spontaneously from them were used as drug carriers to target pyrene to the T cells. In the dark, or in the absence of pyrene, both the intact APC or the shed membranes stimulated interleukin-2 (IL-2) production by the T cells in an antigen-specific way. After UVA (320-400 nm) irradiation, both forms of these drug carriers had an antigen-specific toxic effect on the T hybridoma cells with receptors for the antigen that they carried. Both spontaneous T cell proliferation and antigen-induced IL-2 production were inhibited. The shed membranes had a more antigen-specific toxic effect than the intact APC, which tend to settle out with the T cells in the microtiter plates, possibly causing nonspecific contact.(ABSTRACT TRUNCATED AT 250 WORDS)

Specific suppression of lupus-like graft-versus-host disease using extracorporeal photochemical attenuation of effector lymphocytes

(C57BL/6 x DBA/2)F1 (B6D2F1) mice inoculated with parental DBA/2 (D2) splenocytes develop chronic stimulatory graft-versus-host reaction with many of the clinical manifestations of systemic lupus erythematosus. This investigation tested the ability of 8-methoxypsoralen (8-MOP) and ultraviolet A (UVA) light-treated D2 cells, primed to contain an expanded population of T cells specific for B6D2F1 major histocompatability complex antigens, to treat and/or prevent such systemic lupus erythematosus-like disease. 8-MOP/UVA-treated cells from B6D2F1-primed D2 donors were inoculated into B6D2F1 recipients weekly six to ten times, either before or after initiating graft-versus-host disease with normal D2 cells. A third group of B6D2F1 recipients were vaccinated weekly six times before disease initiation using 8-MOP/UVA-attenuated, B6D2F1-primed D2 cells that had been secondarily stimulated and expanded in vitro in the presence of irradiated B6D2F1 targets and interleukin-2. Control B6D2F1 mice were vaccinated with 8-MOP/UVA-treated D2 cells stimulated in vitro and/or in vivo with (C3H/HeJ x DBA/2)F1 cells. Only mice vaccinated with 8-MOP/UVA-attenuated D2-anti-B6D2F1 cells that were secondarily stimulated and expanded in vitro exhibited differences from controls when measured by the clinical parameters of ascites formation, and mean survival (p < 0.025). These groups also differed significantly in mean antinuclear antibody titer measured 14 weeks after disease initiation (p < 0.05). At 28 weeks, histologic evidence of systemic lupus erythematosus-like kidney disease was found only in the control group. These results indicate that photochemically attenuated D2-anti-B6D2F1 cells primed in vivo and secondarily stimulated and expanded in vitro are capable of vaccinating recipients against progression of graft-versus-host reaction-initiated systemic lupus erythematosus-like disease.

Extracorporeal photopheresis--a new approach for the treatment of cutaneous T cell lymphomas

Extracorporeal photochemotherapy (extracorporeal photopheresis, ECP) is going to become a new alternative in the treatment of cutaneous T cell lymphomas (CTCL), autoimmune disorders, and transplant rejections. After the first promising results in the treatment of CTCL reported in 1987 by Edelson et al. increasing numbers of CTCL patients in a growing number of ECP centers throughout the United States, Europe, and Japan have been successfully treated. Today, it seems that in particular Sézary's syndrome and the erythrodermic variant of mycosis fungoides (MF) respond very well to ECP. Compared to historical controls of MF with lymph node involvement, the median survival of the ECP-treated patients increased from 30 months to up to 60 months. It is our experience that the tumor stage of MF, however, cannot be treated with ECP alone, but is successfully controlled by combination regimens, for example with recombinant interferon alpha. CTCL patients heavily pretreated by polychemotherapy and severe endogenous or iatrogenic immunsuppression do not respond sufficiently and are not good candidates for ECP. The adverse reactions under ECP are well controlled and very low in number. In particular, general immunosuppression by ECP has not been reported so far.

T-cell responses in photoimmune therapy

The extracorporeal inactivation of a lymphocyte rich buffy coat suspension with ultraviolet A light and 8 methoxypsoralen can lead to dramatic clinical improvements following reinfusion of the damaged cells. This therapy is reviewed in the context of the disease it is most commonly used for: cutaneous lymphoma. Studies with cutaneous lymphoma patients have shown an active immune response against purified tumor cells. In addition a mouse model for an impact of therapy on a T-cell lymphoma has demonstrated results that parallel those from clinical studies in humans. The impact of photoimmune therapy on in vivo and in vitro T-cell responses to cutaneous lymphoma is discussed.