Review of Immunomodulation by Photopheresis: Treatment of Cutaneous T-Cell Lymphoma, Autoimmune Disease, and Allograft Rejection

Artificial Organs 18(12):888-897, Blackwell Science, Inc.. Boston 0 1994 Lnternational Society for Artificial Organs

Review of Immunomodulation by Photopheresis: Treatment of Cutaneous T-cell Lymphoma, Autoimmune

Disease, and Allograft Rejection

Jonathan T. Wolfe, Stuart R. Lessin, Anjali H. Singh, and Alain H. Rook

Department of Dermatology, Hospital of the University of Pennsylvania, Philadelphia, Pennsylvania, U . S . A .

Abstract: Photopheresis is an apheresis-based therapy that is currently available at approximately 70 medical centers worldwide. Recent evidence indicates that extracorporeal photopheresis can significantly prolong life as well as induce a 6&75% response rate among individuals with advanced cutaneous T-cell lymphoma (CTCL). Moreover, a 10-15% cure rate, in response to photopheresis alone, or in combination with interferon-cY, has been obtained at our institution. These complete responses have been characterized by the complete disappearance of morphologically atypical cells from the skin and blood. Southern blot analysis of peripheral blood specimens has also confirmed the indefinite disappearance of the malignant T-cell clone from the blood of patients with complete responses. Current immunological data obtained from in vitro human studies and from animal models suggest that the basis for the responses of CTCL patients are related to activation of treated macrophages resulting in release of cytokines, including substantial levels of tumor necro-

sis factor a (TNF-a), and perhaps, to the induction of anticlonotypic immunity directed against pathogenic clones of T lymphocytes. In addition to the treatment of CTCL, a potential role for photopheresis in the therapy of autoimmune disease has been suggested by recent pilot studies of pemphigus vulgaris, rheumatoid arthritis, and systemic lupus erythematosus. Furthermore, a randomized, single-blinded trial involving 79 patients with early onset, aggressive systemic sclerosis suggested that photopheresis could beneficially affect the course of the cutaneous thickening in this form of the disease. Lastly, two independent pilot studies of cardiac transplantation have indicated that photopheresis can reverse acute cardiac allograft rejection and potentially suppress ongoing chronic rejection. Randomized, controlled trials for these new indications for photopheresis therapy are currently in the early stages of implementation. Key Words: Pho- topheresis-Extracorporeal photopheresis-Cutaneous T-cell lymphoma-Allograft rejection.

Extracorporeal photopheresis is a new form of apheresis-based immunomodulatory therapy that is currently approved in the United States by the Food and Drug Administration for the treatment of advanced cutaneous T-cell lymphoma. This therapy is presently available at approximately 70 treatment centers world-wide. At our medical center, photopheresis, with or without other biological response modifiers such as interferon-a (IFN-a) and systemic retinoids, has become a standard therapy for tumor stage as well as the Sezary form of cutaneous

Received December 1993; revised February 1994. Address correspondence and reprint requests to Dr. A.H.

Rook, Department of Dermatology, Hospital of the University of Pennsylvania, 3400 Spruce Street, Philadelphia, PA 19104, U.S.A.

Presented in part at the 9th World Congress of the Interna- tional Society for Artificial Organs, held July 4-8, 1993, Amster- dam, The Netherlands.

T-cell lymphoma. Long-term follow-up of patients who participated in the initial multicenter clinical trial conducted by Edelson and colleagues (1) has indicated that the participants have had significant prolongation of life in comparison with historical controls with a similar burden of disease. More- over, the unprecedented potential for a cure for this devastating malignancy was also realized during this trial since 10% of patients have experienced complete remission with no detectable residual disease for periods of up to 7 years.

In addition, the results of a recent randomized, controlled trial of the treatment of systemic sclerosis with photopheresis, as well as results of several earlier pilot studies that involved the therapy of pemphigus vulgaris, rheumatoid arthritis, and heart transplant rejection, have demonstrated the potential efficacy of photopheresis for autoimmune dis-

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ease and the reversal of solid organ transplant rejection ( 2 4 ) . In this review we will summarize the current use of photopheresis to treat cutaneous T-cell lymphoma, autoimmune disease, and allograft rejection.

CUTANEOUS T-CELL LYMPHOMA

Cutaneous T-cell lymphoma (CTCL) is a clonal lymphoid malignancy of helper T lymphocytes (CD4+). Initial signs of this disease usually appear in the skin as plaques, tumors, or erythroderma, occasionally with concomitant lymphadenopathy and circulating malignant T cells. As the disease progresses, peripheral blood, nodal, and visceral involvement usually become more frequent and extensive. Although a variety of therapies directed at the cutaneous manifestations of CTCL, including electron beam radiation, topical mechlorethamine, and conventional psoralen and ultraviolet A photochemotherapy (PUVA), yield a high rate of initial clinical responses in regard to the skin disease (5,6), these therapeutic regimens appear to have little effect on extracutaneous disease. Furthermore, while multidrug chemotherapy has been recommended for advanced CTCL characterized by multiple tumors, erythroderma, or Sezary syndrome, it does not prolong survival and is associated with a substantial degree of morbidity (7). Thus, the initial multicenter trial of photopheresis conducted by Edelson et al. (8), which used this therapy on 2 successive days monthly for the treatment of eryth- odermic CTCL, yielded highly beneficial results with few if any associated adverse effects. Twenty- four of 29 (83%) erythrodermic patients, with disease resistant to a variety of conventional therapies, showed improvement in their erythroderma with a mean time to development of a positive response within the skin of 22.4 weeks. Moreover, 9 patients (24%) experienced better than a 75% improvement in the extent of their skin lesions while 13 patients (35%) had a 50-75% improvement in their skin lesions. Typically, patients with the most significant degree of improvement had experienced noticeable clearing of their skin by the third or fourth month of treatment.

Quite significantly, in addition to improvement in the cutaneous manifestations of CTCL, a decrease in the extent of peripheral blood involvement was also observed in Edelson’s multicenter trial (8). Among the 6 patients studied who had increased numbers of CD4+ peripheral blood cells prior to therapy, 5 experienced a significant drop in the ab- solute numbers of these cells during their therapy.

This decrease likely indicated a drop in the numbers of circulating malignant cells that bear CD4 on their surface. This conclusion was supported by the observation that the numbers of atypical cells within the peripheral blood with a cerebriform nuclear morphology (Sezary cells) also decreased. Re- cently, Southern blot analysis for T-cell receptor gene rearrangements has indicated that some individuals have had an apparent disappearance of the malignant clone from their peripheral blood in response to photopheresis therapy (9).

At our institution, 5 patients treated with photopheresis who originally had the Sezary syndrome are now in clinical remission without evidence of a peripheral blood malignant T-cell clone on Southern blot analysis. We are presently using more sensitive techniques of molecular diagnosis, specifically the polymerase chain reaction, used together with clone-specific olignucleotide probes (lo), which can permit us to more precisely delineate whether minimal residual disease continues to exist within the blood or skin among individuals in clinical remission.

Continued follow-up of erythrodermic patients who participated in the initial multicenter trial of photopheresis have suggested that this therapy may prolong survival beyond that expected with conventional therapies (1 1). The present median survival of the original 27 erythrodermic patients has exceeded 62.5 months whereas previous studies of a compa- rable patient population, using established therapies, have revealed survival rates of 30-40 months (12). During this period of extended observation, there have been few adverse effects of photopheresis recorded. These results are remarkable in view of recent data demonstrating not only a failure to prolong survival of CTCL patients with the use of intensive multidrug chemotherapeutic regimens combined with electron beam irradiation, but also in light of the high degree of morbidity of such treatment (7). Because of the paucity of adverse effects associated with photopheresis, as well as the potential for the prolongation of life, we frequently em- ploy photopheresis as an initial therapy for advanced stages of CTCL.

Our experience during the last 6 years, and that of other investigators (13), has formed the basis for the development of a clinical profile of those patients most likely to respond to this therapy (Table 1). We routinely recommend this treatment for patients who have either morphological or South- ern blot evidence of circulating malignant cells. Thus, patients with Sezary syndrome or individuals with extensive plaque disease in the presence of

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890 J .T . WOLFE ET AL.

TABLE 1. Profile of CTCL photopheresis responders

Presence of modest or small numbers of peripheral blood

Short duration of disease (<2 years) Normal or near normal numbers of cytotoxic T lymphocytes Normal natural killer cell activity No prior history of intensive chemotherapy Absence of bulky lymphadenopathy or overt visceral disease

Sezary cells (1&20% of mononuclear cells)

atypical peripheral blood cells observed on 1 pm- section analysis of buffy coat specimens are considered to be excellent candidates for photopheresis. In contrast, those without evidence of malignant peripheral blood cells have faired less well at our institution.

No patients with plaque disease covering greater than 10% of the skin surface area, in the absence of peripheral blood involvement, have responded to photopheresis. This is in contrast to patients with a similar degree of skin involvement in the presence of peripheral blood involvement, who have had substantial clinical improvement at our institution. Similarly, erythrodermic patients who lack atypical blood cells are less likely to respond than are those erythrodermic individuals with the full-blown Sezary syndrome. However, those with an espe- cially large tumor burden (white blood count > 15,000/mm3, widespread bulky lymphadenopathy, visceral disease, or numerous cutaneous tumors) are unlikely to respond to photopheresis used as a single treatment modality. Although the authors are aware of several cases of tumor stage disease that have improved while undergoing photopheresis treatment, this form of CTCL is a good example of the need for concurrent therapy with electron beam irradiation with or without IFN-a.

A number of additional clinical and immunological parameters have been identified that may pre- dict responsiveness to photopheresis. In a study of 10 patients with the Sezary syndrome, we deter- mined that normal or near normal numbers of CD8+ peripheral blood T cells correlated with a favorable response to therapy. It could also be concluded that an elevated number of CD4+ T cells was associated with a lack of response to photopheresis. Heald et al. (13) have made similar Observations in regard to T-cell numbers. Since the malignant T cells bear CD4 on their surface, an increase in the numbers of CD4+ cells would appear to indicate an increase in the tumor cell burden, which, as previously stated, correlates with a poor prognosis.

The integrity of the immune response may be a critical factor for patient responsiveness to photopheresis. Our recent results indicate that normal

levels of peripheral blood natural killer (NK) cell activity are usually detected among patients with prominent clinical responses while low levels of NK cell activity are typically measured among nonre- sponders. Taken together with the data related to the peripheral blood T-cell immune profile, these results imply that CD8+ cytolytic and suppressor T cells and NK cells may be important components of the antitumor immune response. Moreover, these data may reflect the requirement for a greater degree of immune integrity to be able to generate an immune response against the photoaltered malignant cells. In fact, these observations are highly relevant to the recent preliminary findings that the malignant clonal T-cell population in CTCL may be susceptible to cell-mediated lysis by autologous cytotoxic T lymphocytes (R.L. Edelson and C. Berger, unpublished observations). Thus, strategies directed at the immunological enhancement of cytotoxic T-lymphocyte function through the use of biological response modifiers may improve the efficacy of photopheresis.

In addition to the immunological parameters shown in Table 1, the extent of prior treatment with immunosuppressive chemotherapy negatively correlates with response to therapy. In fact, studies using animal models of photopheresis have suggested that corticosteroids or immunosuppressive agents can inhibit the desired immunological effects of this therapy (M. Perez and R.L. Edelson, personal communication). Our experience with CTCL patients who have received extensive pretreatment with systemic chemotherapy has revealed that these patients have a lower response rate to photopheresis. Since an intact host immune system appears to be necessary to obtain a response to photopheresis, substantial prior use of immunosuppressive agents may impair the response to this therapy. Previous immunosuppression in transplant patients experiencing active rejection, however, does not appear to alter the response to photopheresis (see below). These observations, along with those indi- cating a low frequency of adverse effects of photopheresis, suggest that this therapy should be considered in the early phases of the clinical man- agement of patients with CTCL who have modest numbers of malignant cells within their peripheral blood.

For patients with disease parameters that place them in a poor prognostic category and that suggest a low probability of having a therapeutic response to photopheresis (extensive prior chemotherapy, large tumor burden, low numbers of peripheral blood CD8+ T cells, depressed N K cell activity),

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adding certain adjunctive therapies in combination with photopheresis may improve the clinical course. We have obtained excellent results using IFN-a in low doses in combination with photopheresis. Patients are started on 2-2.5 million U subcu- taneously 3 times weekly to minimize flu-like symptoms. Doses are gradually increased, as tolerated, to 5-7.5 million U 4 to 5 times weekly. The most typical regimen consists of 3-5 million U every other day. The majority of patients treated in this manner have experienced a significant drop in the numbers of circulating atypical cells in association with improvement in skin disease. In fact, a review of CTCL patients treated at our institution revealed that 11 of 14 patients experienced significant improvement following supplementation of their photopheresis regimen with IFN. Although the IFN is likely playing an exceedingly important role in these responses, the 2 therapies appear to have an addi- tive benefit over either alone.

Other adjuntive therapies used in combination with photopheresis include electron beam therapy, which is frequently used at our institution as a de- bulking procedure for patients with large cutaneous tumors. Although there are anecdotal reports of patients with tumors who responded to photopheresis alone, in our experience, concomitant electron beam therapy, often with IFN-a, is usually required to produce tumor flattening. Use of methotrexate in doses of 15-25 mg weekly or azathioprine daily have also been suggested for patients with elevated white blood cell counts. Although these drugs may provide benefit by impeding the in vivo prolifera- tion of the malignant T cells, one must also consider their potential for suppression of the host response to the photoaltered tumor cells induced by photopheresis.

Corticosteroids are also known to inhibit host immune responses, including NK cell activity and tumor necrosis factor (TNF) production. Treatment- induced TNF may be an important component of the antitumor response. We have recently deter- mined that photopheresis induces the marked production of TNF-a by treated monocytes (14). As a further example of photopheresis-induced immune responses that may be impaired by drugs, we at- tempt to avoid the use of prednisone in our CTCL patients. It is for reasons such as these that we ad- vocate, whenever possible, the use of immune en- hancing agents such as IFN-a rather than potentially immunosuppressive drugs for patients with cutaneous T-cell lymphoma.

Other biological response modifiers that deserve exploration in combination with photopheresis in-

clude IFN-7 and interleukin 12 (IL-12). Both of these cytokines exert substantial immune augmen- tatory effects on cytotoxic T-lymphocyte function. Furthermore, the lymphocytes of patients with CTCL exhibit striking defects in the ability to produce these cytokines (15,16). At present, a limited clinical trial under the direction of Vonderheid and colleagues (Hahnemann University) is in progress to assess the effects of IFN-1, added to photopheresis therapy for patients with Sezary syndrome un- responsive to 6 months of photopheresis alone.

ALLOGRAFT REJECTION AND AUTOIMMUNE DISEASE

As a novel alternative to the use of immunosuppressive drugs, exciting results have been obtained by several groups using photopheresis to reverse acute rejection of heart allografts. Costanzo-Nordin and colleagues at Loyola University (17) were able to rapidly reverse 8 of 9 acute rejection episodes among 7 cardiac allograft recipient patients using photopheresis. In most cases, one treatment, and no more than 2 photopheresis treatments, were ca- pable of arresting the rejection episodes. Moreover, no serious adverse effects of treatment were observed among this patient population.

In a subsequent randomized trial, this same group of investigators compared a single photopheresis treatment with 3 days of high-dose systemic corticosteroids in their ability to reverse cellular rejection of transplanted hearts (18). Following random- ization and treatment of 16 patients, no significant differences were observed in the response rate between the 2 groups.

Barr and colleagues (19) have also employed photopheresis on a long-term basis in an effort to pre- vent the manifestations of chronic graft rejection among cardiac allograft recipients. They reported on a total of 23 patients, 13 of whom received standard triple drug therapy and 10 of whom received monthly photopheresis in addition to standard therapy. Following 1 year of treatment, evaluation employing intravascular ultrasound demonstrated that patients who received combined treatment had significantly less coronary intimal thickening in comparison with those who received standard therapy. Furthermore, those who received combined therapy had a more rapid and sustained drop in serum levels of antibodies directed against allogeneic his- tocompatibility antigens. Thus, if the results of this study are confirmed in a larger multicenter trial, photopheresis will be established as an important immunotherapy that can significantly suppress the

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postcardiac transplant development of intimal hy- perplasia.

Photopheresis has also been used in a variety of autoimmune diseases with encouraging results. An initial study using photopheresis to treat autoimmune disease produced favorable results in patients with pemphigus vulgaris who were resistant to corticosteroids and immunosuppressive drugs (3) . Four patients with long-standing active disease, despite prolonged courses of treatment with high doses of prednisone in combination with cyclophos- phamide or azathioprine, responded to photopheresis. All patients initially showed improvement in the extent of their skin disease which allowed for significant tapering of other medications. Three of the 4 patients eventually experienced long-term re- missions permitting discontinuation of all treatment. Significant reductions in serum levels of an- tiepidermal cell immunoglobulin G occurred in conjunction with clinical improvement. Although relapses occurred in all 3, remission was easily re- induced following three to four additional monthly cycles of photopheresis. It is our experience that once clinical improvement occurs, gradual tapering of corticosteroids and immunosuppressive medications can proceed. However, simultaneous abrupt tapering of photopheresis along with the tapering of other medications may result in the early recur- rence of skin lesions. Photopheresis produced no serious adverse effects in any of the 4 patients during several years of follow up.

Recently, photopheresis has been successfully employed to treat systemic sclerosis (4). Substantial skepticism has arisen regarding the use of photopheresis for systemic sclerosis since it manifests primarily as a fibrosing disease with increased de- position of collagen within the skin and involved visceral organs. Despite its status as a fibrosing disease, recent observations have implicated the immune system as a prime factor in the genesis of the increased collagen production (20,21). Elevated serum levels of soluble IL-2 receptors in patients with active clinical disease support the association of T-cell activation with disease progression. Further- more, biopsy of involved tissues early in the evolu- tion of the clinical disease has revealed the infiltra- tion of activated helper T cells which may be releasing certain cytokines, particularly transforming growth factor p (TGF-P), which is a potent stim- ulator of collagen synthesis (22).

An initial pilot study used photopheresis to treat 2 patients with systemic sclerosis with rapidly progressive skin thickening (23). In the first case, a 60-year-old male had a 6-month history of disease

with skin thickening involving greater than 80% of the body surface, mild pulmonary involvement, proteinuria (1,300 mg/24 h), severe Raynaud’s phenomenon with ulcerated digits, and evidence of mi- croangiopathic hemolysis. Marked clinical improvement was observed within the first several months of treatment with the photopheresis being administered on 2 consecutive days every 4 weeks. By the third month of therapy, the proteinuria, the hemolysis, and the Raynaud’s phenomenon were no longer evident. After 1 year of therapy, the only residual disease was mild skin thickening of the hands with acrosclerosis. Treatment of a second patient with extensive skin thickening also resulted in significant skin softening and a decrease in the area of cutaneous involvement.

These initial results were followed by the perfor- mance of a multicenter, randomized, single-blinded trial to examine the efficacy and safety of photopheresis in the reversal and prevention of progression of skin disease in systemic sclerosis of recent onset and rapid development (4). Seventy-nine patients with systemic sclerosis of recent onset (mean duration of symptoms was 1.83 years) and progressive skin involvement entered a randomized, paral- lel group clinical trial comparing photopheresis given on 2 consecutive days every 4 weeks to treatment with D-penicillamine. Skin severity scores (skin hardening), percent skin surface area involvement, hand closure, and oral aperture were evaluated monthly by examiners who were blinded to the nature of the treatment. A variety of other evalua- tions including pulmonary function tests, skin biop- sies, and serologies were obtained at baseline and after 6 and 12 months of treatment. During this trial 56 patients received 6 months of therapy (31 received photopheresis) while 47 received 10 months of therapy (29 on photopheresis). By 6 months of treatment, 21 of 31 (68%) patients who received photopheresis had experienced significant softening of the skin in Comparison to 8 of 25 (32%) who received D-penicillamine. It is noteworthy that whereas only 3 of 31 (10%) of those who received photopheresis had experienced significant worsening of their skin severity score after 6 months of treatment, 8 of 25 (32%) who received D-penicillamine had significant worsening. Thus, in the early phases of treatment, a significantly higher response rate was obtained with photopheresis (p = 0.02). At both the 6- and lomonth evaluation point, the mean skin severity score, mean percent involvement, and mean oral aperture measurements were measurably improved from baseline among those who received photopheresis. Mean right and left hand

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closure measurements had also improved significantly by 10 months of therapy. Skin biopsy studies demonstrated an association between clinical improvement and decreased thickness of the dermal layer.

It is noteworthy that adverse effects of photopheresis were minimal during this trial and did not require discontinuation of treatment by any of the patients. In contrast, 25% of patients who received D-penicillamine were required to permanently dis- continue this drug due to side effects or rapid progression of disease while on this therapy. Thus, photopheresis appears to produce early improvement with few side effects when used for aggressive cases of recent onset systemic sclerosis.

In addition to studies involving pemphigus and systemic sclerosis, the results of recent pilot studies have suggested the potential efficacy of photopheresis for rheumatoid arthritis (2) and systemic lupus erythematosus (24). Other clinical indications currently being studied in clinical trials include multiple sclerosis ( 2 5 ) , insulin-dependent diabetes mellitus, and AIDS-related complex (26).

Studies in our laboratory have indicated that photopheresis does not produce measurable suppression of T-cell responses against recall protein antigens, such as tetanus toxoid, nor does it suppress primary immune responses against de novo protein antigens such as Keyhole Limpet hemocyanin (27). However, it is possible that this therapy induces specific suppression of responses against alloanti- gens, as suggested by the observations of Perez et al. (28), using a murine model of cutaneous al- lografting. These latter observations are particularly relevant to the early clinical findings that photopheresis can reverse rejection of transplanted hearts. Nevertheless, it should be emphasized that significant clinical evidence of photopheresis- induced immunosuppression, such as the development of neoplasia or opportunistic infections has not been observed. Thus, the fact that photopheresis produces minimal adverse effects and provides substantial benefit for a number of immune mediated diseases indicates that this therapy has clear- cut advantages in comparison to chemotherapeutic and immunosuppressive agents in the treatment of these conditions.

PHOTOPHERESIS PROCEDURE

The treatment is accomplished using the UVAR photopheresis system (Therakos, West Chester, PA) as previously described for cutaneous T-cell lymphoma (8). Two hours following the ingestion of

8-MOP (0.5 mg/kg oxsoralen ultra), patients un- dergo a discontinuous leukapheresis procedure with exposure of removed leukocytes to ultraviolet A radiation. During the procedure, approximately 240 ml of leukocyte-enriched blood is mixed with 300 ml of the patient’s plasma and 200 ml of sterile normal saline plus approximately 10,000 U of heparin. (We have occasionally found the need for greater con- centrations of heparin when treating patients with systemic sclerosis due to heightened coagulability). The final buffy coat preparation contains an esti- mated 25-50% of the total peripheral blood mononuclear cell compartment and has a hematocrit from 2.5-7%. The buffy coat is then passed as a 1 mm film through a sterile cassette surrounded by ultraviolet A emitting bulbs, permitting a 180 min exposure to ultraviolet A light, yielding an average exposure per lymphocyte of 2 J/cm’. Following exposure of the cells to ultraviolet A, the buffy coat is returned to the patient. The entire procedure re- quires approximately 3.5 h.

Throughout the course of treatment, psoralen levels require occasional assessment. Plasma levels at or above 100 ng/ml or levels within the photopheresis buffy-coat bag above 50 ng/ml are recommended. Substantial intraindividual variation in psoralen absorption can occur depending upon gas- tric contents and disease state. For example, patients with systemic sclerosis who have bowel involvement may have extremely poor absorption of the 8-MOP. If this aspect of their disease worsens, absorptive capacity may diminish, thus requiring an increase in dose. It is not unusual for some patients to have marked variations in plasma psoralen levels from treatment to treatment without a discernable cause. Thus, measurements are taken several times annually to assure the maintenance of therapeutic levels of 8-MOP. The recent development of a new liquid form of psoralen, which has been used by Knobler et al. (29), and which is currently in clinical trial in the United States, can be mixed directly with the leukocytes within the UVAR device. This will permit the precise pharmacological regulation of 8-MOP levels in the future, and it will obviate the need for oral administration of 8-MOP, which should remove nausea due to the 8-MOP, which is one of the few known side effects of photopheresis.

Occasionally, obtaining vascular access prior to the leukapheresis phase of treatment may be diffi- cult. This may not be an uncommon problem among patients with systemic sclerosis or long-standing diabetes mellitus. Since reasonably high venous flow rates are required for the treatment (25-50 mlh in ) , intermittent femoral vein cannulation is recom-

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mended in such instances. The regular use of in- dwelling Hickman catheters has resulted in frequent infection at our center; therefore, venous porta- catheters are preferred if this family of catheters is to be used. Vascular grafts such as A-V fistulas can also be used although their flow rates far exceed what is necessary to perform photopheresis.

ADVERSE EFFECTS

Our experience since 1985 is that photopheresis has been extremely well tolerated. The most common adverse effect has been the sporadic occur- rence of psoralen-induced nausea. This is usually mild with a duration of only 30-60 min. It occasionally can be associated with vomiting and diaphore- sis. If nausea is recurrent, the dosing can be stag- gered. For example, each 10 mg capsule can be administered every 10 min. This split dose regimen typically produces satisfactory blood levels within 2 h of the last capsule, yet nausea often can be eliminated (F. Gasparro, personal communication).

Hypotension occurs uncommonly during the leukapheresis phase, particularly among those taking antihypertensive agents or diuretics. These medications are often held until the conclusion of the treatment. As an alternative, small volumes of normal saline may be infused just prior to the initiation of the treatment as a preventive measure. In most cases, patients with advanced cardiomyopathy and aortic stenosis have tolerated photopheresis without difficulty. These observations indicate that substantial homeostatic derangements of vascular vol- ume are often required for the development of hypotension.

Low grade fevers occurring 4-12 h after reinfu- sion of the treated cells is common during the early phases of therapy in patients with CTCL. Patients are usually asymptomatic and antipyretics are not needed. Fever appears to be unrelated to bacter- emia and is associated with the most marked clinical responses to treatment. Recent observations indicate that photopheresis is responsible for the induction of proinflammatory and pyrogenic cytokines from monocytes. This immunologic effect is the likely cause for the posttreatment febrile response. Nevertheless, since this therapy involves venous cannulation of the frequently immunosup- pressed patient, it is recommended that blood cul- tures be obtained and that all potential sources of infection be evaluated.

Although normal leukocytes are exposed to psoralen and ultraviolet during the photopheresis procedure itself, depletion of these blood elements has

not been noted. Furthermore, clinical evidence of photopheresis induced immunosuppression such as the development of neoplasia or opportunistic infections has not been observed. Thus the fact that photopheresis produces minimal adverse effects and can provide substantial benefit indicates that this therapy has clear advantages in comparison to chemotherapeutic and immunosuppressive agents.

MECHANISM OF ACTION OF PHOTOPHERESIS

At present, the dominant mechanism of action of photopheresis remains undefined. Nevertheless, a substantial body of new information is rapidly emerging that suggests that multiple mechanisms are likely interacting to produce the desired therapeutic effect. In regard to the biological effects of psoralen, ultraviolet A irradiation activates psoralen contained within leukocytes leading to the crosslinking of DNA which ultimately results in the proliferative arrest of treated cells (30). Large or activated mononuclear cells may be particularly sensitive to the antiproliferative effects of %MOP and ultraviolet A, possibly due to an increased number of psoralen binding sites on the cell membrane. This observation may account for the apparent heightened susceptibility to photopheresis of the large, malignant T cells that are typical of CTCL. Similarly, activated T cells within the peripheral blood of patients with autoimmune disease are likely targets for psoralen- and ultraviolet A-mediated damage. Thus, the treated cells are rapidly eliminated from the body simply by the process of “photodestruction. ”

It is noteworthy that photodestruction of pathogenic T cells probably represents only a minor mode of action of photopheresis since removal of malignant T cells from patients with Sezary syndrome by leukapheresis at the same, or even greater frequency than photopheresis, often has little effect on disease progression. Moreover, the fact that each photopheresis procedure, performed on 2 consecutive days every 4 weeks, photoalters just 2-5% of the entire in vivo white cell pool suggests that specific antitumor responses are being induced. With the recent finding that the malignant clone of T cells is susceptible to lysis by autologous cytotoxic T lymphocytes (R.L. Edelson and C. Berger, unpublished observations), investigators will be able to directly assess whether photopheresis produces a direct enhancement of this immunological phenomenon.

Of great relevance to the augmentation of antitu-

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mor responses is our observation that photopheresis induces the release of inflammatory mediators from mononuclear cells. Monocytes isolated following the photopheresis treatment are found to be producing large quantities of TNF as compared with untreated cells (14). This finding has important implications for the treatment of CTCL as well as for systemic sclerosis. In regard to CTCL, TNF can augment a number of antitumor immune responses, including cytotoxic T cell responses, and this cytokine may also exert a direct cytotoxic effect on lymphoma cells (31). In the case of systemic sclerosis, TNF has been recently shown to inhibit collagen synthesis by skin fibroblasts (21). In addition to the stimulation of TNF release, photopheresis also induces the release of other lymphokines including IL-1 and IL-6. Since these are all monocyte- dependent cytokines, photopheresis may nonspe- cifically activate peripheral blood monocyte/ macrophages which results in the production of this constellation of cytokines.

Other important mechanisms of action of photopheresis have been suggested by recent observations using a number of different experimental animal models. Study of the murine model of experimental allergic encephalitis has been espe- cially revealing in regard to understanding the mechanisms of photopheresis (32). In this model, rats injected with myelin basic protein develop a paralytic illness associated with T-cell destruction of the nervous system. The pathogenic T cells that mediate this destruction can be isolated and cloned in vitro. When naive syngeneic rats are inoculated with the cloned T cells, all of the features of experimental allergic encephalitis are reproduced. How- ever, if the pathogenic clones are first treated with psoralen and ultraviolet A and then infused, the animals are protected from the development of disease upon subsequent challenge with the pathogenic T cells. Protection from disease appears to be mediated by the generation of clone-specific suppressor T cells that have developed in response to the psoralen- and ultraviolet A-modified pathogenic cells. Perez and colleagues (28), employing a model of cutaneous allograft rejection, have similarly obtained evidence of stimulation of an antigen-specific suppressor T-cell response when alloreactive effector 1. cells are treated with psoralen and ultraviolet A and infused into syngeneic animals. These results indicate, that at least in the setting of these animal models, an active immunization process can occur following the administration of photoinactivated syngeneic T-cell clones.

Because of its efficacy in the treatment of dis-

eases of immune activation, concern has been ex- pressed regarding the potential immunosuppressive effects of photopheresis. As cited above, photopheresis does not appear to significantly alter host immune responses to T-cell-dependent soluble protein antigens, such as tetanus toxoid (14). In addition, our recent findings indicated that a panel of delayed-type hypersensitivity skin tests placed on 7 patients with systemic sclerosis remained unaltered following 6 months of photopheresis therapy (14). These results, taken together with the observations that there is not an increased incidence of opportunistic infections or neoplasia among photopheresis- treated patients, suggest that this therapy does not profoundly suppress cell-mediated immunity.

CONCLUSIONS Extracorporeal photopheresis is a promising new

form of therapy which has been shown to be effica- cious in a number of disease states (Table 2). The benefits of photopheresis include its lack of toxicity and demonstrable immunosuppressive side effects. Since photopheresis specifically targets activated lymphocytes, the fact that transplant patients in active rejection exhibit marked T-cell activation serves as a rationale for the possibility of down- regulating rejection activity with this therapy. Al- though the precise mechanism of action is unclear, photopheresis may be manipulating T-cell-derived cytokines, clone-specific suppressor cells, and/or antigen presenting cells in a fashion that alters immune-mediated destruction of transplanted tissue. Careful investigative dissection of the responses af- fected by this immunotherapy are underway. De- spite this lack of detailed understanding, photopheresis has shown promise as a safe and nontoxic immunomodulator for patients with CTCL, a variety of autoimmune diseases, and, most recently, in heart transplant patients experiencing organ rejection (17). Photopheresis has also doubled graft survival and reversed rejection activity in heart xenotransplantation models while inhibiting mixed lymphocyte culture responses (33). In the future, photopheresis may serve as an immunosuppressive sparing agent or as a “bridge” providing valuable time for patients who are searching for new organs

TABLE 2. Potentid indications for photopheresis

Advanced cutaneous T-cell lymphoma (FDA approved) Immunosuppressive drug resistant pemphigus vulgaris Scleromyxedema Systemic lupus erythematosus Rheumatoid arthritis Systemic sclerosis Allograft rejection

Artif Organs, Vol. 18. No. 12. 1994


while experiencing uncontrolled rejection of previously transplanted tissue. In this context, a multi- centered clinical trial is being developed to explore the efficacy and safety of photopheresis in the treat-

use of photopheresis as a potent immune modulator continues to be extended bevond dermatologic con-

12. Sausville EA, Eddy JL, Makuch RW, Fischmann AB, Schechter GP, Matthews M, Glatstein E, Ihde DC, Kaye F, Veach SR, et al. Histopathologic staging at initial diagnosis of mycosis fungoides and the Sezary syndrome. Definition of three distinctive prognostic groups. Ann Intern Med 1988; 109: 372-82.

Edelson R. Photopheresis therapy of cutaneous T-cell lymphoma: The Yale-New Haven Hospital experience. Yale J

merit Of advancing cardiac rejection* The 13, Heald p, Perez M, Christensen I, Dobbs N, McKiernan G,

Y

ditions in the hope that other patients will benefit Biol Med 1989;62:629-38. 14. Vowels BR, Cassin M, Boufal MH, Walsh LJ, Rook AH.

Extracorporeal photochemotherapy induces the production from its effects. of tumor necrosis factor-alpha by monocytes: Implications for the treatment of cutaneous T cell lymphoma and systemic sclerosis. J Invest Dermatol 1992;98:686-92.

15. Rook AH, Vowels BR, Jaworsky C, Singh A, Lessin SR. The immunopathogenesis of cutaneous T cell lymphoma: Abnormal cytokine production by Sezary T cells. Arch Der- ma to1 I993 ; 129:486-9.

Acknowledgment: This work was supported in part by grants RO lCA58841-01, R29 CA-5501, R29 CA-55017, and MO1 RR 00040-29 the Institutes Of Health, by a Veterans Administration Career Develop- ment Award (RA-1710), and by research support from Therakos, Inc.

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Documents

Review of Immunomodulation by Photopheresis: Treatment of Cutaneous T-Cell Lymphoma, Autoimmune Disease, and Allograft Rejection