Anja Rabenhorst

Cutaneous manifestations in patients with mastocytosis: Consensus report of the European Competence Network on Mastocytosis; the American Academy of Allergy, Asthma & Immunology; and the European Academy of Allergology and Clinical Immunology.

Cutaneous lesions in patients with mastocytosis are highly heterogeneous and encompass localized and disseminated forms. Although a classification and criteria for cutaneous mastocytosis (CM) have been proposed, there remains a need to better define subforms of cutaneous manifestations in patients with mastocytosis. To address this unmet need, an international task force involving experts from different organizations (including the European Competence Network on Mastocytosis; the American Academy of Allergy, Asthma & Immunology; and the European Academy of Allergology and Clinical Immunology) met several times between 2010 and 2014 to discuss the classification and criteria for diagnosis of cutaneous manifestations in patients with mastocytosis. This article provides the major outcomes of these meetings and a proposal for a revised definition and criteria. In particular, we recommend that the typical maculopapular cutaneous lesions (urticaria pigmentosa) should be subdivided into 2 variants, namely a monomorphic variant with small maculopapular lesions, which is typically seen in adult patients, and a polymorphic variant with larger lesions of variable size and shape, which is typically seen in pediatric patients. Clinical observations suggest that the monomorphic variant, if it develops in children, often persists into adulthood, whereas the polymorphic variant may resolve around puberty. This delineation might have important prognostic implications, and its implementation in diagnostic algorithms and future mastocytosis classifications is recommended. Refinements are also suggested for the diagnostic criteria of CM, removal of telangiectasia macularis eruptiva perstans from the current classification of CM, and removal of the adjunct solitary from the term solitary mastocytoma.

Mast cells play a protumorigenic role in primary cutaneous lymphoma

Primary cutaneous lymphomas (PCLs) are clonal T- or B-cell neoplasms, which originate in the skin. In recent years, mast cells were described as regulators of the tumor microenvironment in different human malignancies. Here, we investigated the role of mast cells in the tumor microenvironment of PCL. We found significantly increased numbers of mast cells in skin biopsies from patients with cutaneous T-cell lymphoma (CTCL) and cutaneous B-cell lymphoma (CBCL). Mast cell infiltration was particularly prominent in the periphery, at lymphoma rims. Interestingly, CTCL and CBCL patients with a progressive course showed higher mast cell counts than stable patients, and mast cell numbers in different stages of CTCL correlated positively with disease progression. In addition, mast cell numbers positively correlated with microvessel density. Incubating primary CTCL cells with mast cell supernatant, we observed enhanced proliferation and production of cytokines. In line with our in vitro experiments, in a mouse model of cutaneous lymphoma, tumor growth in mast cell-deficient transgenic mice was significantly decreased. Taken together, these experiments show that mast cells play a protumorigenic role in CTCL and CBCL. Our data provide a rationale for exploiting tumor-associated mast cells as a prognostic marker and therapeutic target in PCL.

Interleukin-31: A Novel Diagnostic Marker of Allergic Diseases

Interleukin-31 (IL-31) is a newly discovered cytokine associated with chronic skin inflammation and pruritus. Patients with atopic dermatitis, chronic spontaneous urticaria, allergic contact dermatitis, prurigo nodularis, primary cutaneous lymphoma and mastocytosis exhibit increased serum levels of IL-31 protein and elevated IL-31 mRNA in the skin. Interestingly, in some of these diseases, IL-31 serum levels correlate with disease activity. In the present review, we particularly focus on studies investigating IL-31 as a novel diagnostic biomarker indicating the severity of allergic diseases. We highlight a recent study on IL-31 in mastocytosis, which reports on elevated serum levels of IL-31 in adults correlating with the severity of disease categories, tryptase levels and percentage of bone marrow infiltration. We conclude that growing knowledge about IL-31, its receptors and signaling pathways serves to better understand the pathogenesis of allergic diseases and may lead to the development of novel treatment approaches.

Large maculopapular cutaneous lesions are associated with favorable outcome in childhood-onset mastocytosis

BACKGROUND Mastocytosis, characterized by pathologic accumulation of mast cells, can manifest itself in adulthood or childhood. Pediatric patients usually have cutaneous mastocytosis (CM) with mast cell infiltrates limited to the skin and spontaneous improvement of skin lesions after several years. However, there are some patients with persistent disease resembling adulthood-onset mastocytosis. OBJECTIVE The current classification of CM differentiates between 3 subforms. In clinical practice we noticed that different variants of these subforms might exist, particularly in patients with childhood-onset mastocytosis. Therefore, in the present study, we aimed to investigate whether specific cutaneous lesions in patients with childhood-onset mastocytosis are associated with other disease parameters. METHODS We analyzed 144 patients with a disease onset of less than age 17 years using a systematic dermatologic approach. RESULTS One hundred twenty-two patients presented with maculopapular cutaneous mastocytosis (MPCM), 12 patients presented with diffuse CM, and 10 patients presented with solitary mastocytoma of the skin. Patients with MPCM showed particularly heterogeneous cutaneous lesions and were therefore grouped into 3 variants presenting either with small lesions (MPCM-small, skin lesions <1 cm in diameter; n = 19), large lesions (MPCM-large, skin lesions ≥ 1 cm in diameter; n = 89), or atypical lesions (MPCM-other, n = 14). Patients with MPCM-large lesions, compared with those with MPCM-small lesions, were characterized by significantly lower tryptase levels, shorter disease duration, and earlier disease onset. In addition, more patients with MPCM-large lesions exhibited spontaneous regression of cutaneous lesions. CONCLUSION Our data show that patients with MPCM-large lesions compared with those with MPCM-small lesions have a more favorable disease course and suggest exploring the size of cutaneous lesions as a prognostic parameter in childhood-onset MPCM.

Cre/loxP-Based Mouse Models of Mast Cell Deficiency and Mast Cell-Specific Gene Inactivation

Over the past decades, research on in vivo functions of mast cells has largely relied on kit-mutant mouse strains. Recently, new mouse models for investigation of mast cell functions based on the Cre/loxP recombination system have been published and results in these new models challenged findings of previous studies in kit-mutant mice. Herein we describe procedures central to mast cell-specific gene inactivation and the generation of mast cell-deficient mice based on the mouse strain Mcpt5-Cre, which expresses Cre recombinase selectively in connective tissue mast cells.

Development and validation of the mastocytosis quality of life questionnaire: MC-QoL.

Mastocytosis is a heterogeneous disease characterized by a clonal expansion of mast cells in various organs. The vast majority of patients affected suffer from signs and symptoms caused by mediator release from mast cells. Although the disease burden is high, there is currently no specific instrument to measure health‐related quality of life (HRQoL) impairment in patients with mastocytosis.

Anti-Fas/CD95 and tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) differentially regulate apoptosis in normal and neoplastic human basophils

Abstract Basophilia is associated with allergic and parasitic diseases and advanced chronic myeloid leukemia. In the present study, we characterized the expression and function of the death receptors Fas/CD95 and tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) receptors in basophils from healthy donors compared to neoplastic basophils. Peripheral blood basophils obtained from healthy donors (HD-PBB) and from patients with chronic myeloid leukemia (CML-PBB) were found to express high levels of Fas/CD95 and low levels of TRAIL-R2, whereas the basophil-like chronic myeloid leukemia cell line KU-812 expressed significant levels of TRAIL-R1 and TRAIL-R2. HD-PBB underwent apoptosis in response to anti-Fas/CD95, but showed resistance to TRAIL, unless they were co-treated with actinomycin D. Interestingly, CML-PBB and KU-812 cells exhibited the opposite response pattern with resistance to anti-Fas/CD95, but significant susceptibility to TRAIL-induced apoptosis. Our data show that anti-Fas/CD95 and TRAIL differentially regulate apoptosis of normal and neoplastic human basophils, which may direct the development of novel therapeutic strategies.

Dimethylfumarate induces apoptosis in human mast cells

Mast cells modulate autoimmune diseases such as psoriasis and multiple sclerosis. Fumaric acid esters (FAEs) are widely used for the treatment of psoriasis, and dimethylfumarate (DMF) has recently been approved for multiple sclerosis. In this study, we analysed the cytotoxic effect of FAEs on human mast cells. Specifically, cell death was analysed in the human mast cell line HMC‐1 and in primary cord blood‐derived mast cells (CBMCs) after incubation with fumaric acid (FA), monomethylfumarate (MMF), DMF and calcium bis(monomethylfumarate) (Ca‐MF). Our data show that only DMF potently induces apoptotic cell death in HMC‐1 cells and CBMCs. DMF‐mediated apoptosis was associated with increased expression of Bax and Bak and activation of caspase‐9 and caspase‐6. Interestingly, DMF also enhanced the sensitivity of CBMCs towards TRAIL‐ and dexamethasone‐induced apoptosis. These findings demonstrate for the first time that DMF induces apoptosis of human mast cells, primarily via the mitochondrial apoptotic pathway. Our study contributes to the understanding of the beneficial effects of FAEs in autoimmune diseases and provides a rationale for exploiting FAEs for other diseases associated with mast cells.

Targeting Tumor-Infiltrating B Cells in Cutaneous T-Cell Lymphoma

Introduction The tumor microenvironment and infiltrating immune cells are important for cancer biology and progression which has been exploited therapeutically in recent years. Whereas infiltrating T cells, macrophages, or natural-killer (NK) cells have been extensively analyzed, recent studies also suggest a role for B cells in cancer biology. Primary cutaneous T-cell lymphomas (CTCL) represent a heterogeneous group of extranodal non-Hodgkin lymphomas of which the most common subtype is mycosis fungoides (MF). At early stages ( IIA; European Organisation for Research and Treatment of Cancer [EORTC]/International Society for Cutaneous Lymphomas [ISCL]), MF usually runs an indolent course with almost normal life expectancy. However, advanced-stage MF ( IIB), the folliculotropic MF subtype (FMF) and also Sézary syndrome (SS) are more aggressive (median survival, 13-48 months). Preclinical data suggest that chronic inflammation promotes CTCL progression with a critical role for macrophages and mast cells. Occasionally, B-cell infiltrations have been reported in CTCL and although a well-established CTCL model is lacking, B-cell deficient mice exhibited significant regressions of EL4-T-cell lymphoma grafts. Therefore, we analyzed diagnostic skin biopsies of 33 consecutively treated CTCL patients for infiltrating B cells (CD20/ CD79a) and reviewed respective clinical data from 1979 to 2011 (Table 1). Psoriasis and eczema tissues served as controls. Staging followed ISCL/EORTC criteria. Lymphoma-tissues containing 50 B-cells/mm of lymphoma-infiltrate were assigned as B-cell positive. The study was approved by the institutional review board (No. 08-144). Immunohistochemistry revealed remarkable differences of CD20 B-cell infiltrates between CTCL subtypes (Fig 1A) and additional flow-cytometric analysis in available frozen samples supported the B-cell nature of CD20 cells (Fig 3A). Eighteen out of 33 CTCL patients (MF [n 25], FMF [n 5], SS [n 3]) had significantly increased median B-cell numbers within the lymphoma infiltrate, whereas controls (psoriasis [n 5], eczema [n 5]) were B-cell negative (Fig 1B and Table 1). Remarkably, all FMF and SS cases showed significantly increased median B-cell numbers compared with classic MF. However, in classic MF 40% of the cases were B-cell positive. Given the fact that FMF and SS represent more aggressive subtypes, we asked whether B-cell infiltrations correspond with the clinical stage and behavior. Comparison of B-cell infiltrates in early ( IIB) versus advanced ( IIB) stages revealed a significant correlation of B-cell positivity with advanced stages. This correlation not only applied to the entire CTCL cohort but also to classic MF cases solely (Fig 1C). Moreover, clinical data analyses revealed a significant correlation of B-cell infiltrates with progression-free survival (PFS). As shown in Figure 1D, patients with B-cell positive lymphoma had a significantly shortened median PFS, ie, 50 months (entire cohort) and 126 months (classic MF only). In contrast, median PFS in B-cell negative cases was not reached at the end of observation (360 months).

Activation of KIT modulates the function of tumor necrosis factor-related apoptosis-inducing ligand receptor (TRAIL-R) in mast cells.

Mastocytosis is characterized by the accumulation of mast cells (MCs) associated with activating mutations of KIT. Tumor necrosis factor‐related apoptosis‐inducing ligand receptors (TRAIL‐Rs) are preferentially expressed on neoplastic cells and induce the extrinsic apoptotic pathway. Recent studies reported on the expression of TRAIL‐Rs and TRAIL‐induced apoptosis in cultured human MCs, which depend on stem cell factor (SCF)‐induced or constitutive KIT activation.