Stimulatory autoantibodies to PDGF receptor in patients with extensive chronic graft-versus-host disease

Diagnosis and treatment of pulmonary chronic GVHD: report from the consensus conference on clinical practice in chronic GVHD

This consensus statement established under the auspices of the German working group on BM and blood stem cell transplantation (DAG-KBT), the German Society of Hematology and Oncology (DGHO), the Austrian Stem Cell Transplant Working Group, the Swiss Blood Stem Cell Transplantation Group (SBST) and the German-Austrian Pediatric Working Group on SCT (Päd-Ag-KBT) summarizes current evidence for diagnosis, immunosuppressive and supportive therapy to provide practical guidelines for the care and treatment of patients with pulmonary manifestations of chronic GVHD (cGVHD). Pulmonary cGVHD can present with obstructive and/or restrictive changes. Disease severity ranges from subclinical pulmonary function test (PFT) impairment to respiratory insufficiency with bronchiolitis obliterans being the only pulmonary complication currently considered diagnostic of cGVHD. Early diagnosis may improve clinical outcome, and regular post-transplant follow-up PFTs are recommended. Diagnostic work-up includes high-resolution computed tomography, bronchoalveolar lavage and histology. Topical treatment is based on inhalative steroids plus beta-agonists. Early addition of azithromycin is suggested. Systemic first-line treatment consists of corticosteroids plus, if any, continuation of other immunosuppressive therapy. Second-line therapy and beyond includes extracorporeal photopheresis, mammalian target of rapamycin inhibitors, mycophenolate, etanercept, imatinib and TLI, but efficacy is limited. Clinical trials are urgently needed to improve understanding and treatment of this deleterious complication.

Graft-vs-Host Disease following Allogeneic Hematopoietic Cell Transplantation

Background

Allogeneic hematopoietic cell transplantation (HCT) is a potentially curative therapy with proven efficacy in the management of hematologic malignancies. However, it is complicated by the syndromes of acute and chronic graft-vs-host disease (GVHD).

Methods

A narrative review is provided to summarize major biologic insights into the pathogenesis of these immune-mediated disorders, as well as advances in diagnosis, classification, prevention, management, and allied supportive care with the aim of providing essential understanding for clinicians with or without subspecialty experience in the field of blood and marrow transplantation.

Results

Major scientific advances have contributed to enhanced understanding of the pathogenesis of these disorders, and clinical investigation has provided more effective preventive and therapeutic strategies for GVHD. However, since acute GVHD and chronic GVHD remain leading sources of transplantation-related morbidity and mortality, ongoing investigation is needed to develop new approaches to addressing these syndromes.

Conclusions

The major challenge for future investigation will be to capitalize on biologic insights in order to develop novel strategies for the prevention and therapy of acute and chronic GVHD that will address the current shortcomings in existing therapeutic approaches.

Novel treatment concepts for graft-versus-host disease

Acute and chronic graft-versus-host disease (GVHD) are potentially lethal complications after stem cell transplantation (SCT). Steroids are the appropriate first-line treatment for both. However, if patients do not adequately benefit from steroid therapy, mortality is high and standardized treatment algorithms are lacking. This is mainly because of limited data from prospective, randomized clinical trials. In addition, most of the available treatment options only induce clinical benefits in a limited proportion of patients. Thus, there is an urgent clinical need to develop more potent immunosuppressive treatment strategies for patients suffering from acute or chronic steroid-refractory GVHD while maintaining the graft versus tumor effect to avoid a potential rise in relapse-related mortality. The increasing knowledge about host- as well as donor-derived variables favoring GVHD development and the increasing armamentarium of immune-modulatory agents entering preclinical and clinical research will probably allow more effective treatment of GVHD in the future. This review describes novel developments in the treatment of steroid-refractory GVHD, with a special focus on the rationale behind promising pharmacologic compounds or up-coming cellular therapies.

B cell homeostasis and the development of chronic graft-versus-host disease: implications for B cell-depleting therapy

Chronic graft-versus-host disease (GVHD) is a serious complication that develops frequently in survivors of allogeneic stem cell transplant. Since elucidation of the role of B cells in the pathogenesis of chronic GVHD, B cell-depleting therapy with rituximab has been associated with beneficial effects in clinical and laboratory studies in patients with chronic GVHD. Although the mechanism underlying the contribution of B cells to the development of chronic GVHD is poorly understood, recent studies have proposed that B cell reconstitution after allogeneic stem cell transplant is involved in the development of chronic GVHD. Inadequate reconstitution of naive B cells and the persistence of high levels of B cell-activating factor have been found in patients with chronic GVHD, and these changes might be associated with the expansion of activated CD27-positive B cells that produce autoantibody in chronic GVHD. In the light of this altered B cell homeostasis in chronic GVHD, the role of rituximab in controlling the clinical manifestations of chronic GVHD has been studied. In this review, we address the role of B cells in the pathogenesis of chronic GVHD and the response to B cell-depleting therapy based on B cell homeostasis.

Mouse models of graft-versus-host disease: advances and limitations

The limiting factor for successful hematopoietic stem cell transplantation (HSCT) is graft-versus-host disease (GvHD), a post-transplant disorder that results from immune-mediated attack of recipient tissue by donor T cells contained in the transplant. Mouse models of GvHD have provided important insights into the pathophysiology of this disease, which have helped to improve the success rate of HSCT in humans. The kinetics with which GvHD develops distinguishes acute from chronic GvHD, and it is clear from studies of mouse models of GvHD (and studies of human HSCT) that the pathophysiology of these two forms is also distinct. Mouse models also further the basic understanding of the immunological responses involved in GvHD pathology, such as antigen recognition and presentation, the involvement of the thymus and immune reconstitution after transplantation. In this Perspective, we provide an overview of currently available mouse models of acute and chronic GvHD, highlighting their benefits and limitations, and discuss research and clinical opportunities for the future.

A phase 1 study of imatinib for corticosteroid-dependent/refractory chronic graft-versus-host disease: response does not correlate with anti-PDGFRA antibodies

Stimulatory antiplatelet derived growth factor receptor α (PDGFRA) antibodies have been associated with extensive chronic graft-versus-host disease (cGVHD). We performed a phase 1 dose escalation trial of imatinib in corticosteroid-dependent/refractory cGVHD to assess the safety of imatinib and test the hypothesis that abrogation of PDGFRA signaling can ameliorate the manifestations of cGVHD. Fifteen patients were enrolled. Mean follow-up time was 56.6 weeks (range, 18-82.4 weeks). Imatinib 400 mg daily was associated with more frequent moderate to life-threatening adverse events than 200 mg daily. The main adverse events were nausea, edema, confusion, diarrhea, liver function test elevation, fatigue, and myalgia. The overall response rate was 40% (6 of 15). The treatment failure rate was 40% (6 of 15). Twenty percent (3 of 15) of subjects had stable disease. Of 4 subjects with phospho-PDGFRA and phospho-PDGFRB immunohistochemistry studies before and after treatment, inhibition of phosphorylation was observed in 3 but correlated with response in one. Anti-PDGFRA antibodies were observed in 7 of 11 evaluable subjects but correlated with clinical activity in 4. We conclude that cGVHD responds to imatinib through multiple pathways that may include PDGFRA signal transduction. This study is registered at www.clinicaltrials.gov as #NCT00760981.

Targeting tyrosine kinases: a novel therapeutic strategy for systemic sclerosis

PURPOSE OF REVIEW

This article reviews the current evidence and rationale for the use of tyrosine kinase inhibitors as potential therapeutic interventions for systemic sclerosis.

RECENT FINDINGS

The signaling cascades of the profibrotic cytokines transforming growth factor-β and platelet-derived growth factor utilize tyrosine kinases. Preclinical studies have suggested potential efficacy of tyrosine kinase inhibitors in fibrosing disorders. Imatinib, dasatinib, and nilotinib treatment of scleroderma and normal fibroblasts leads to decreased production of extracellular matrix proteins in an in-vitro model. Several murine models demonstrate decreased skin thickening with tyrosine kinase inhibition. Case reports and one open-label trial suggest potential efficacy of imatinib in diffuse systemic sclerosis, although adverse events are common. One controlled and several uncontrolled trials are ongoing, and their results will better define the role of tyrosine kinase inhibition in the treatment of this disorder.

SUMMARY

Tyrosine kinase inhibition as a potential strategy for the treatment of systemic sclerosis has been gaining more widespread interest based on preclinical data and open-label experiences. Large, multicenter, double-blind, randomized controlled trials are needed to assess the efficacy and safety of this approach in this complex disease.

The pathophysiology of chronic graft-versus-host disease: the unveiling of an enigma

Chronic graft-versus-host disease (CGVHD) is one of the most significant complications of long-term survivors after allogeneic hematopoietic stem cell transplantation (allo-HSCT). CGVHD may have protean manifestations and can pose unique diagnostic and therapeutic challenges. New recommendations that emphasize the importance of qualitative differences, as opposed to time of onset after HSCT, are now being used to standardize the diagnosis and clinical assessment of CGVHD, but they require validation. During the past 3 decades, experimental studies and clinical observations have elucidated the mechanisms of acute GVHD, but its biology is much less well-understood. Experimental studies have generated at least 4 theories to explain the pathophysiology of CGVHD: (1) thymic damage and the defective negative selection of T cells, (2) regulatory T cell deficiencies, (3) auto-antibody production by aberrant B cells, and (4) the formation of profibrotic lesions. Mouse models have provided important insights into the pathophysiology of CGVHD, and these have helped improve clinical outcomes following allo-HSCT, but no animal model fully replicates all of the features of CGVHD in humans. In this article, recent clinical changes, the pathogenesis of CGHVD, the cellular and cytokine networks implicated in its pathogenesis, and the animal models used to devise strategies to prevent and treat CGVHD are reviewed.

Biomarkers in chronic graft-versus-host disease

Chronic graft-versus-host disease (cGVHD ) is a leading cause of allogeneic hematopoietic stem-cell transplantation-related mortality and morbidity. It is an immune-mediated disorder that can target almost any organ in the body, often with devastating consequences. The immune-suppressive medications currently used to treat it are equally toxic and are often not very effective. At this time, our understanding of its pathophysiology is limited. The discovery of potential biomarkers offers new possibilities in the clinical management of cGVHD. They could potentially be used for diagnosing cGVHD, for predicting or evaluating response to therapy and for unique insights into the pathophysiology underlying the clinical manifestations of cGVHD. Understanding the biological origins of these biomarkers can help us construct a more comprehensive and clinically relevant model for the pathogenesis of this disease. In this article, we review existing evidence for candidate biomarkers that have been identified in the framework of how they may contribute to the pathophysiology of cGVHD. Issues regarding the discovery and application of biomarkers are discussed.

The pathogenesis of systemic sclerosis

Systemic sclerosis (SSc), also known as scleroderma, is a rare connective tissue disease characterized by vascular and immune dysfunction, leading to fibrosis that can damage multiple organs. Its pathogenesis is complex and poorly understood. Two major clinical subtypes are the limited and diffuse forms. Research into SSc has been hampered by its rarity, its clinical heterogeneity, and the lack of mouse models that accurately recapitulate the disease. Clinical and basic studies have yielded some mechanistic clues regarding pathogenesis. Recent insights gained through the use of microarrays have revealed distinctive subsets of SSc within and beyond the limited and diffuse subsets. In this review, we discuss potential mechanisms underlying the vascular, autoimmune, and fibrotic points of dysregulation. Proper categorization of SSc patients for research studies by use of microarrays or other biomarkers is critical, as disease heterogeneity may explain some of the inconsistencies of prior studies.

A case of sclerodermatous graft-versus-host disease responsive to imatinib therapy

Sclerodermatous graft-versus-host disease (sGVHD) is a rare, late complication of hematopoietic cell transplantation. Classified as a variant of chronic graft-versus-host disease, sGVHD is thought to be predominantly an immune-mediated response characterized by aberrant T-cell function and dysregulation of tyrosine kinase cascades. Recently, the profibrotic cytokine transforming growth factor B and stimulatory autoantibodies against the platelet-derived growth factor receptor have been implicated in the pathogenesis of sGVHD. Treatment of sGVHD remains disappointing and largely limited by systemic side effects. Imatinib mesylate is a small molecule tyrosine kinase inhibitor that has been shown to selectively inhibit both the platelet-derived growth factor receptor and transforming growth factor-β signaling pathways. We report a case of sGVHD in a pediatric patient that was resistant to traditional therapy but showed improvement in cutaneous symptoms following daily treatment with 400 mg of imatinib mesylate. Due to its favorable side-effect profile, specificity for molecular pathways deranged in sGVHD and proven efficacy in other sclerodermoid diseases, imatinib mesylate is a promising new tool in the management of this challenging disease.

Gene expression profile of cytokines in patients with chronic graft-versus-host disease after allogeneic hematopoietic stem cell transplantation with reduced conditioning

There are no reliable markers useful to predict the onset or the evolution of chronic graft-versus-host disease (cGVHD) after allogeneic hematopoietic stem cell transplantation (HSCT), although several candidate biomarkers have been identified from limited hypothesis-driven studies. In this study we evaluated 14 patients who received a reduced intensity conditioning HSCT. Seven patients had cGVHD, whereas 7 never developed cGVHD during the period of observation. The expression of 114 cytokines in immunoselected cell populations was explored by microarray analysis and 11 cytokines were selected for further evaluation by real-time PCR. Differential gene expression measurements showed a significant up-regulation for INFγ (interferon, gamma) in CD8+ and for TNFSF3 (tumor necrosis factor superfamily, member 3) and for TNFSF10 (tumor necrosis factor superfamily, member 10) in CD14+ cell population when comparing cGVHD with control samples. The expression levels were significantly decreased for TNFSF10 in CD8+ cell population and for TNFSF12 (tumor necrosis factor superfamily, member 12) and for PDGFβ (platelet-derived growth factor, beta) in CD4+. Our data seem to suggest that different immune populations can play a role in cGVHD pathogenesis and the early detection of gene expression profile in these patients could be useful in the monitoring of GVHD. We hypothesized that PDGFβ down-regulation could represent a negative feedback to compensate for enhanced expression of its receptor recently reported.

Coagulation and autoimmunity in scleroderma interstitial lung disease

OBJECTIVES

Interstitial lung disease in systemic sclerosis (SSc-ILD) is often an irreversible and progressive fibrosing process that now is the leading cause of scleroderma-related deaths. In this review we present our current understanding of the role played by coagulation and particularly by thrombin in autoimmune-mediated tissue injury and fibrosis, mainly as it relates to SSc-ILD.

METHODS

We used PubMed to search for articles published up to October 2010 for keywords referring to autoimmunity, coagulation, pulmonary fibrosis, and scleroderma.

RESULTS

SSc-ILD is an autoimmune disease associated with lymphocyte activation and release of various cytokines and growth factors. The production of autoantibodies is a central feature in SSc. Activation of the coagulation cascade with release of thrombin is 1 of the earliest events following tissue injury. Thrombin contributes to autoimmune responses by activating of pathogenic Th2 lymphocyte profile in SSc. Thrombin also modulates tissue repair responses, stimulates transformation of epithelial cells, endothelial cells, and fibroblasts into myofibroblast phenotype, and induces secretion of several pro-immune and profibrotic factors, which serve as antigens for pathogenic autoantibodies production in SSc-ILD.

CONCLUSIONS

The identification of links between autoimmunity and coagulation would provide new insights into the pathogenesis of pulmonary fibrosis associated with autoimmune diseases and further acknowledge the importance of thrombin in the development of SSc-ILD.

Fibrosis and immune dysregulation in systemic sclerosis

Autoimmune and inflammatory phenomena are characteristically present in systemic sclerosis (SSc) and impact on dysregulated fibroblast extracellular matrix deposition, hallmark of the disease in conjunction with fibroproliferative vasculopathy. Oligoclonal T helper 2-like cells are present in the skin and peripheral blood in early diffuse disease. Type 2 cytokines synergize with profibrotic cytokines including transforming growth factor beta, favoring collagen deposition and metalloproteinase inhibition by fibroblasts. Furthermore, chemokine with pro-fibrotic and pro-angiogenic properties are preferentially produced by fibroblasts under the influence of Th2-like cells. The profibrotic monocyte chemotactic protein 1 is also produced by fibroblasts, partially in response to Toll-like receptor 4 (TLR4) recognition, when autoantibodies (autoAb) bind to fibroblast surface. In addition, immune-complex formed by autoAb and ubiquitous antigens including topoisomerase-1 favor the production of interferon-alpha (IFN-α) possibly by interacting with intravesicular TLRs. Consistent with this findings, unbiased gene screening has revealed that SSc peripheral blood cells express genes induced by IFN-α, a characteristic shared with systemic lupus erythematosus and other autoimmune disorders. These findings highlight the complex relationship between adaptive and acquired immune responses, which may participate to the pathogenesis of SSc in manners until now unsuspected, which may help in identifying novel therapeutic targets.

Pathogenesis and management of graft-versus-host disease

Allogeneic hematopoietic cell transplantation (HCT) is an important therapeutic option for various malignant and nonmalignant conditions. As allogeneic HCT continues to increase, greater attention is given to improvements in supportive care, infectious prophylaxis, immunosuppressive medications, and DNA-based tissue typing. However, graft versus host disease (GVHD) remains the most frequent and serious complication following allogeneic HCT and limits the broader application of this important therapy. Recent advances in the understanding of the pathogenesis of GVHD have led to new approaches to its management, including using it to preserve the graft versus leukemia effect following allogeneic transplant. This article reviews the important elements in the complex immunologic interactions involving cytokine networks, chemokine gradients, and the direct mediators of cellular cytotoxicity that cause clinical GVHD, and discusses the risk factors and strategies for management of GVHD.

Tyrosine kinases in inflammatory dermatologic disease

Tyrosine kinases (TKs) are enzymes that catalyze the phosphorylation of tyrosine residues on protein substrates. They are key components of signaling pathways that drive an array of cellular responses including proliferation, differentiation, migration, and survival. Specific TKs have recently been identified as critical to the pathogenesis of several autoimmune and inflammatory diseases. Small-molecule inhibitors of TKs are emerging as a novel class of therapy that may provide benefit in certain patient subsets. In this review, we highlight TK signaling implicated in inflammatory dermatologic diseases, evaluate strategies aimed at inhibiting these aberrant signaling pathways, and discuss prospects for future drug development.

Allogeneic hematopoietic cell transplantation: the state of the art

Allogeneic hematopoietic cell transplantation (HCT) is a potentially curative procedure for a variety of hematologic malignancies. The field has evolved substantially over the past decade, with advances in patient and donor selection, stem cell sources, supportive care, prevention of complications and reduced-toxicity preparative regimens. As a result, the indications for HCT and the pool of eligible patients have expanded significantly. In this article, we provide an overview of the major aspects of allogeneic HCT, and focus specifically on areas of active research and on novel approaches to challenges in the field. Specifically, we will discuss approaches to reduce the toxicity of the preparative regimen, with the goal of increasing the safety and applicability of HCT. The availability of suitable donors may be an obstacle to wider application of HCT. We review three major approaches to broadening the donor pool: the use of HLA-mismatched unrelated donors, umbilical cord blood and HLA-haploidentical family donors. Graft-versus-host disease remains a major cause of morbidity and mortality after HCT. We review recent advances in the understanding of this phenomenon, and novel prophylactic and therapeutic approaches that hold the promise of further improving the safety of the procedure. We conclude with a speculative outline of the next 5 years of research in the field of HCT.

Clinical, serologic and instrumental data of ten patients affected by sclerodermatous chronic graft versus host disease: similarities and differences in respect to systemic sclerosis

Chronic graft versus host disease (cGVHD), the most common late complication of allogeneic haematopoietic stem cell transplantation (HSCT), may present with sclerodermatous lesions resembling in some cases the cutaneous involvement of systemic sclerosis (SSc). Certain pathogenetic findings connect the two diseases. In this report we describe ten subjects affected by cGVHD who underwent the examinations routinely carried out to stage SSc patients. Demographic, clinical, serologic and instrumental data were recorded. These patients showed differences in appearance, extent and progression of the sclerodermatous lesions with greater involvement of the trunk and proximal part of the limbs than the extremities. In seven subjects ANA test was positive; scleroderma-associated autoantibodies were not detected in any of the cases. Moreover, typical organ involvement of SSc was not found. Only one patient developed Raynauds phenomenon after HSCT and only one patient demonstrated a nailfold videocapillaroscopic scleroderma pattern. Except for cutaneous involvement of cGVHD, that may resemble SSc, the clinical features of the two diseases are quite different, suggesting that the fibrotic process characterizing cGVHD and SSc has different etiologies and different initial pathobiologic events.

Stem cell mobilization with G-CSF induces type 17 differentiation and promotes scleroderma

The recent shift to the use of stem cells mobilized by granulocyte colony-stimulating factor (G-CSF) for hematopoietic transplantation has increased chronic graftversus-host disease (GVHD), although the mechanisms of this are unclear. We have found that G-CSF invokes potent type 17 rather than type 1 or type 2 differentiation. The amplification of interleukin-17 (IL-17) production by G-CSF occurs in both CD4 and CD8 conventional T cells and is dependent on, and downstream of, G-CSF-induced IL-21 signaling. Importantly, donor IL-17A controls the infiltration of macrophages into skin and cutaneous fibrosis, manifesting late after transplantation as scleroderma. Interestingly, donor CD8 T cells were the predominant source of IL-17A after transplantation and could mediate scleroderma independently of CD4 T cells. This study provides a logical explanation for the propensity of allogeneic stem cell transplantation to invoke sclerodermatous GVHD and suggests a therapeutic strategy for intervention.

Anti-CD13 Abs in children with extensive chronic GVHD and their relation to soluble CD13 after allogeneic blood and marrow transplantation from a Children's Oncology Groups Study, ASCT0031

Our group previous demonstrated a strong association between elevated plasma soluble CD13 enzyme activity and newly diagnosed extensive chronic graft-versus-host disease (cGVHD) in children. Since cytotoxic anti-CD13 antibodies have been documented after blood and marrow transplant in association with cytomegalovirus infection and cGVHD, we hypothesized soluble CD13 contributes to cGVHD pathogenesis by induction of CD13 reactive antibodies and that anti-CD13 antibodies could be additional biomarkers for newly diagnosed pediatric extensive cGVHD. Using prospectively collected plasma samples from pediatric allogeneic blood and marrow transplant subjects with cGVHD and controls without cGVHD enrolled in a large multi-institution Children's Oncology Group cGVHD therapeutic trial we evaluated whether soluble CD13 correlates with induction of anti-CD13 antibodies. We found that CD13 reactive antibodies are present in a proportion of patients after allogeneic BMT, but did not appear to correlate with the presence of soluble CD13. Anti-CD13 antibodies also did not meet our criteria as a diagnostic biomarker for cGVHD. These data are not able to confirm that induction of CD13 reactive antibodies is a mechanism for cGVHD in children nor are part of the pathogenesis of cGVHD associated with elevated soluble CD13. The exact role of CD13 in cGVHD remains to be determined.

Chronic graft-versus-host disease (GVHD) in children

Five-year survival rates for childhood cancer now exceed 80% and with the significant progress made by the transplant community in developing less toxic conditioning regimens and in the treatment of posttransplant complications, allo-hematopoietic stem cell transplantation (HSCT) contributes significantly to that population of long-term survivors. In this context, the acute and long-term toxicities of chronic graft-versus-host disease (cGVHD) have an ever-increasing effect on organ function, quality of life, and survival; patients and families who initially felt great relief to be cured from the primary disease, now face the challenge of a chronic debilitating illness for which preventative and treatment strategies are suboptimal. Hence, the development of novel strategies that reduce and or control cGVHD, preserve graft-versus-tumor effects, facilitate engraftment and immune reconstitution, and enhance survival after allo-HSCT represents one of the most significant challenges facing physician-scientists and patients.

Emerging role of CD20 blockade in allogeneic hematopoietic cell transplantation

There is growing evidence incriminating B lymphocytes in the pathogenesis of graft-versus-host disease (GVHD). Better understanding of the role of B lymphocytes has uncovered new therapeutic approaches, such as CD20 blockade, which appear to be improving outcomes in allogeneic hematopoietic cell transplant recipients. Administration of the chimeric murine/human anti-CD20 monoclonal antibody, rituximab, prior to hematopoietic cell allografting or as part of preparative regimens appears to reduce treatment-related mortality and to improve posttransplant outcomes mainly by decreasing the incidence and severity of acute GVHD. This beneficial effect of rituximab has not had an impact, to the same extent on the incidence of chronic GVHD, which remains a significant cause of morbidity and mortality following hematopoietic cell allografting. Alternatively, rituximab has been shown to be effective for treatment of cGVHD, but data is limited because of the lack of randomized controlled clinical trials and the small sample size in most of the published series. Incorporation of rituximab into the therapeutic armamentarium of Epstein-Barr virus-associated posttransplant lymphoproliferative disorder has clearly improved the overall prognosis of this dreadful disease. This review highlights the evolving role of CD20 blockade in allogeneic hematopoietic cell transplantation and the need to continue to refine B cell depletion strategies in this setting.

Is there a role for B-cell depletion as therapy for scleroderma? A case report and review of the literature

OBJECTIVES

Rituximab (RTX) has been successfully used in the treatment of several rheumatic diseases with an acceptable safety profile. We present herein a patient with systemic sclerosis (SSc) who exhibited significant improvement of his lung function and skin fibrosis following RTX administration, and review the literature regarding the role of B-cells in SSc and the potential efficacy of RTX in its treatment.

METHODS

We performed an internet search using the keywords systemic sclerosis, scleroderma, rituximab, B-cells, fibrosis, interstitial lung disease (ILD), and therapy.

RESULTS

Our patient, a 40-year old man with severe SSc-associated ILD, received 4 courses of RTX. The patient's lung function improved; forced vital capacity and diffusing capacity of carbon monoxide reached values of 35% and 33%, respectively, compared with 30% and 14% of pretreatment values. Skin thickening assessed clinically and histologically improved as well. Several lines of evidence suggest that B-cells may have a pathogenic role in SSc. B-cells from tight skin mice--an animal model of SSc--exhibit chronic hyperactivity; likewise, B-cells from patients with SSc overexpress CD19 and are chronically activated. Furthermore, studies have revealed that B-cell genes were specifically transcribed in SSc skin and that B-cell infiltration was a prominent feature of SSc-associated ILD. The potential clinical efficacy of RTX in SSc has been explored in a limited number of patients with encouraging results. Preliminary data suggest that RTX may favorably affect skin as well as lung disease in SSc.

CONCLUSIONS

Several basic research data underscore the potential pathogenic role of B-cells in SSc and clinical evidence suggests that RTX might be a therapeutic option in SSc. Large-scale multicenter studies are needed to evaluate the potential clinical efficacy of RTX in SSc.

The role of B cells in the pathogenesis of graft-versus-host disease

Allogeneic hematopoietic stem cell transplantation is an established treatment modality for malignant and nonmalignant hematologic diseases. Acute and chronic graft-versus-host diseases (GVHDs) are a major cause of morbidity and mortality after allogeneic stem cell transplantation. T cells have been identified as key players in the graft-versus-host reaction and, therefore, most established drugs used against GVHD target T cells. Despite our knowledge on the pathogenesis of the GVH reaction, success of established therapies for prevention and treatment of GHVD is unsatisfactory. Recently, animal and human studies demonstrated that B cells are involved in the immunopathophysiology of acute and chronic GVHD. Early phase clinical trials of B-cell depletion with rituximab have shown beneficial effects on both acute and chronic GVHD. This review summarizes the current experimental and clinical evidence for the involvement of B cells in the pathogenesis of acute and chronic GVHD and discusses the clinical implications for the management of patients undergoing allogeneic stem cell transplantation.

Magic bullet, part III?

In this issue of Blood, Oliveri and colleagues and Magro and colleagues report pilot trials using imatinib for steroid refractory sclerotic cGVHD,showing response rates of 79%and 50%.

Imatinib for refractory chronic graft-versus-host disease with fibrotic features

We previously reported that patients with fibrotic, chronic graft-versus-host disease (cGVHD) have antibodies activating the platelet-derived growth factor receptor pathway. Because this pathway can be inhibited by imatinib, we performed a pilot study including 19 patients with refractory cGVHD, given imatinib at a starting dose of 100 mg per day. All patients had active cGVHD with measurable involvement of skin or other districts and had previously failed at least 2 treatment lines. Patient median age was 29 years (range, 10-62 years), and median duration of cGvHD was 37 months (range, 4-107 months). The organs involved were skin (n = 17), lung (n = 11), and bowel (n = 5); 15 patients had sicca syndrome. Imatinib-related, grade 3 to 4 toxicity included fluid retention, infections, and anemia. Imatinib was discontinued in 8 patients: in 3 because of toxicity and in 5 because of lack of response (n = 3) or relapse of malignancy (n = 2). Overall response rate at 6 months was 79%, with 7 complete remissions (CRs) and 8 partial remissions (PRs). With a median follow-up of 17 months, 16 patients are alive, 14 still in CR or PR. The 18-month probability of overall survival is 84%. This study suggests that imatinib is a promising treatment for patients with refractory fibrotic cGVHD.

Cutaneous chronic graft-versus-host disease does not have the abnormal endothelial phenotype or vascular rarefaction characteristic of systemic sclerosis

BACKGROUND

The clinical and histologic appearance of fibrosis in cutaneous lesions in chronic graft-versus -host disease (c-GVHD) resembles the appearance of fibrosis in scleroderma (SSc). Recent studies identified distinctive structural changes in the superficial dermal microvasculature and matrix of SSc skin. We compared the dermal microvasculature in human c-GVHD to SSc to determine if c-GVHD is a suitable model for SSc.

METHODOLOGY/PRINCIPAL FINDINGS

We analyzed skin biopsies of normal controls (n = 24), patients with SSc (n = 30) and c-GVHD with dermal fibrosis (n = 133)). Immunostaining was employed to identify vessels, vascular smooth muscle, dermal matrix, and cell proliferation. C-GVHD and SSc had similar dermal matrix composition and vascular smooth muscle pathology, including intimal hyperplasia. SSc, however, differed significantly from c-GVHD in three ways. First, there were significantly fewer (p = 0.00001) average vessels in SSc biopsies (9.8) when compared with c-GVHD (16.5). Second, in SSc, endothelial markers were decreased significantly (19/19 and 12/14 for VE cadherin and vWF (p = <0.0001 and <0.05), respectively). In contrast, 0/13 c-GVHD biopsies showed loss of staining with canonical endothelial markers. Third, c-GVHD contained areas of microvascular endothelial proliferation not present in the SSc biopsies.

CONCLUSIONS/SIGNIFICANCE

The sclerosis associated with c-GVHD appears to resemble wound healing. Focal capillary proliferation occurs in early c-GVHD. In contrast, loss of canonical endothelial markers and dermal capillaries is seen in SSc, but not in c-GVHD. The loss of VE cadherin in SSc, in particular, may be related to microvascular rarefaction because VE cadherin is necessary for angiogenesis. C-GVHD is a suitable model for studying dermal fibrosis but may not be applicable for studying the microvascular alterations characteristic of SSc.

Anti-moesin antibodies derived from patients with aplastic anemia stimulate monocytic cells to secrete TNF-alpha through an ERK1/2-dependent pathway

Antibodies specific to moesin, which are frequently detectable in the serum of patients with aplastic anemia (AA), can induce tumor necrosis factor-alpha (TNF-alpha) secretion from monocytes and a human monocytic leukemia cell line THP-1. We investigated the mechanisms responsible for TNF-alpha secretion from monocytic cells induced by the auto-antibodies that are purified from the sera of AA patients. TNF-alpha induction by anti-moesin antibodies depended on the amount of cell surface moesin expressed by THP-1 cells. F(ab')(2) fragments prepared from the anti-moesin antibodies were able to stimulate THP-1 cells to secrete TNF-alpha and this stimulatory effect was enhanced by cross-linking of moesins with anti-human IgG F(ab')(2) fragment antibodies. Anti-moesin antibodies as well as their F(ab')(2) fragments induced the phosphorylation of ERK1/2 in monocytic cells and this effect was suppressed by the addition of an ERK1/2 inhibitor. Moreover, anti-moesin antibody treatment induced the phosphorylation of moesin proteins in the monocytes and THP-1 cells within 30 min. These results indicate that anti-moesin antibodies induce TNF-alpha secretion from monocytes through the activation of the ERK1/2 pathway provoked by direct binding to moesin on the cells.

Lack of detection of agonist activity by antibodies to platelet-derived growth factor receptor alpha in a subset of normal and systemic sclerosis patient sera

OBJECTIVE

To investigate whether agonist anti-platelet-derived growth factor receptor alpha (anti-PDGFRalpha) antibodies are present in the serum of patients with systemic sclerosis (SSc; scleroderma).

METHODS

Sera were obtained from healthy subjects and scleroderma patients. An electrochemiluminescence binding assay was performed for detection of serum autoantibodies to PDGFRalpha, PDGFRbeta, epidermal growth factor receptor (EGFR), and colony-stimulating factor receptor 1 (CSFR1). Serum immunoglobulin was purified by protein A/G chromatography. To assess Ig agonist activity, PDGFRalpha-expressing cells were incubated with pure Ig and the level of receptor phosphorylation determined in an enzyme-linked immunoassay, as well as by Western blotting. Ig agonist activity was also assessed in a mitogenic assay and by MAP kinase activation in a PDGFRalpha-expressing cell line.

RESULTS

Sera from 34.3% of the healthy subjects and 32.7% of the SSc patients contained detectable autoantibodies to PDGFRalpha and PDGFRbeta, but not EGFR or CSFR1. Purified Ig from these sera was shown to retain PDGFR binding activity and, at 200-1,000 microg/ml, exhibited no agonist activity in a cell-based PDGFRalpha phosphorylation assay and did not stimulate a mitogenic response or MAP kinase activation in a PDGFRalpha-expressing cell line. Two purified Ig samples that were unable to bind PDGFRalpha did exhibit binding activity to a nonglycosylated form of PDGFRalpha.

CONCLUSION

Although approximately one-third of sera from scleroderma patients contained detectable autoantibodies to PDGFR, these antibodies were not specific to scleroderma, since they were also detected in a similar percentage of samples from normal subjects. PDGFRalpha agonist activity was not demonstrated when purified Ig from these sera was tested in cell-based assays.

Regulation of platelet-derived growth factor receptor function by integrin-associated cell surface transglutaminase

A functional collaboration between growth factor receptors such as platelet derived growth factor receptor (PDGFR) and integrins is required for effective signal transduction in response to soluble growth factors. However, the mechanisms of synergistic PDGFR/integrin signaling remain poorly understood. Our previous work showed that cell surface tissue transglutaminase (tTG) induces clustering of integrins and amplifies integrin signaling by acting as an integrin binding adhesion co-receptor for fibronectin. Here we report that in fibroblasts tTG enhances PDGFR-integrin association by interacting with PDGFR and bridging the two receptors on the cell surface. The interaction between tTG and PDGFR reduces cellular levels of the receptor by accelerating its turnover. Moreover, the association of PDGFR with tTG causes receptor clustering, increases PDGF binding, promotes adhesion-mediated and growth factor-induced PDGFR activation, and up-regulates downstream signaling. Importantly, tTG is required for efficient PDGF-dependent proliferation and migration of fibroblasts. These results reveal a previously unrecognized role for cell surface tTG in the regulation of the joint PDGFR/integrin signaling and PDGFR-dependent cell responses.

Inflammation and bone marrow transplantation

The procedural requirements of bone marrow transplantation (BMT) predispose to the dramatic induction of local and systemic inflammatory states and can be conceived in relation to transplant conditioning, the activation of alloreactive T cells and finally, the effector stage of graft-versus-host disease (GVHD). It is now clear that alloreactive T cell responses result in a dramatic and often fulminant amplification of systemic inflammation that is responsible for many of the characteristic causes of transplant-related mortality. The pathways by which inflammatory cytokines are induced after BMT and the resultant pathologies will be discussed.

Innovative approaches to treat steroid-resistant or steroid refractory GVHD

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

Altered B-cell homeostasis and excess BAFF in human chronic graft-versus-host disease

Chronic graft-versus-host disease (cGVHD) causes significant morbidity and mortality in patients otherwise cured of malignancy after hematopoietic stem cell transplantation (HSCT). The presence of alloantibodies and high plasma B cell-activating factor (BAFF) levels in patients with cGVHD suggest that B cells play a role in disease pathogenesis. We performed detailed phenotypic and functional analyses of peripheral B cells in 82 patients after HSCT. Patients with cGVHD had significantly higher BAFF/B-cell ratios compared with patients without cGVHD or healthy donors. In cGVHD, increasing BAFF concentrations correlated with increased numbers of circulating pre-germinal center (GC) B cells and post-GC "plasmablast-like" cells, suggesting in vivo BAFF dependence of these 2 CD27(+) B-cell subsets. Circulating CD27(+) B cells in cGVHD comprised in vivo activated B cells capable of IgG production without requiring additional antigen stimulation. Serial studies revealed that patients who subsequently developed cGVHD had delayed reconstitution of naive B cells despite persistent BAFF elevation as well as proportional increase in CD27(+) B cells in the first year after HSCT. These studies delineate specific abnormalities of B-cell homeostasis in patients with cGVHD and suggest that BAFF targeting agents may be useful in this disease.

Oral graft-versus-host disease

OBJECTIVE

Graft-versus-host disease (GVHD) is a leading cause of morbidity and mortality in patients receiving hematopoietic cell transplant. It is estimated that 40-70% of engrafted patients surviving the initial transplant eventually develop chronic GVHD (cGVHD), which can persist for months to years and require long-term management from multiple disciplines. This review describes the oral component of this transplant complication.

DESIGN

The search related to GVHD patho-biology, salivary gland disease after hematopoietic cell transplant and treatments for oral GVHD encompassed literature from 1966 through 2008. Searches were limited to the MEDLINE/PubMed database and English language literature in peer-reviewed journals.

RESULTS

Our understanding of the patho-biology of oral cGVHD is based on studies of other affected tissues. It is difficult to determine the prevalence and incidence of salivary gland disease after transplant because there is no universally accepted case definition. In general, clinical trials for treatment of oral cGVHD have been too small to make strong recommendations for use in clinical practice.

CONCLUSIONS

Larger well-designed clinical studies are needed to understand the patho-biology of oral cGVHD and determine best treatments for this disease.

Immune modulation and chronic graft-versus-host disease

As more and more patients undergoing allogeneic hematopoietic SCT (HSCT) survive the early post-transplant period, the number of individuals at risk for chronic GVHD has grown. Treatment for established cGVHD remains unsatisfactory. No experimental agent has demonstrated superiority to steroids alone in a randomized clinical trial. Distinguishing chronic from acute graft-versus-host disease is a major issue. The importance of achieving clarity in cGVHD diagnosis is critical as efforts are undertaken to understand its pathogenesis and to design definitive trials that can target prevention and/or treatment. Immune tolerance to self-antigens may be broken in cGVHD, giving rise to the autoimmune manifestations of the disorder. Recent attention has focused on CD4+CD25 regulatory T cells and their relationship to cGVHD. Significant enthusiasm has emerged for manipulating Treg either ex vivo or in vivo for clinical benefit. Another immunomodulatory approach to cGVHD might be the targeting of B lymphocytes and the antibodies they produce. As efforts continue to devise strategies to treat and prevent chronic GVHD, it is important to acknowledge the link between cGVHD and freedom from relapse, at least for certain malignancies.