Marie Fischer

Mast cell CD30 ligand is upregulated in cutaneous inflammation and mediates degranulation-independent chemokine secretion

Mast cells are involved in many disorders where the triggering mechanism that leads to degranulation and/or cytokine secretion has not been defined. Several chronic inflammatory diseases are associated with increased mast cell numbers and upregulation of the TNF receptor family member CD30, but the role of elevated CD30 expression is poorly understood. Here we report what we believe to be a novel way to activate mast cells with CD30 that leads to degranulation-independent secretion of chemokines. CD30 induced a de novo synthesis and secretion of the chemokines IL-8, macrophage inflammatory protein-1alpha (MIP-1alpha), and MIP-1beta, a process involving the MAPK/ERK pathway. Mast cells were found to be the predominant CD30 ligand-positive (CD30L-positive) cell in the chronic inflammatory skin diseases psoriasis and atopic dermatitis, and both CD30 and CD30L expression were upregulated in lesional skin in these conditions. Furthermore, the number of IL-8-positive mast cells was elevated both in psoriatic and atopic dermatitis lesional skin as well as in ex vivo CD30-treated healthy skin organ cultures. In summary, characterization of CD30 activation of mast cells has uncovered an IgE-independent pathway that is of importance in understanding the entirety of the role of mast cells in diseases associated with mast cells and CD30 expression. These diseases include Hodgkin lymphoma, atopic dermatitis, and psoriasis.

Mast cells express functional CD30 ligand and are the predominant CD30L-positive cells in Hodgkin's disease

Hodgkins disease (HD) tumours are characterized by the presence of few tumour cells, the Hodgkin and Reed‐Sternberg (HRS) cells, surrounded by a large amount of non‐neoplastic cells. The role of this cell infiltrate for the development of HD is not known. CD30, belonging to the tumour necrosis factor receptor superfamily, is highly expressed on HRS cells and believed to be involved in tumourigenesis and tumour progression. Tumour samples from 42 patients were immunohistochemically double‐stained for tryptase, a mast cell‐specific proteinase and CD30 ligand (CD30L). Tryptase‐positive mast cells were present in all tumours. Of these cells, 50% expressed CD30L and 66% of the CD30L‐positive cells were mast cells. CD30L mRNA in in vitro developed normal mast cells and malignant human and murine mast cell lines was detected using reverse transcription polymerase chain reaction. CD30L protein expressed on human mast cells was detected using flow cytometry. In a co‐culture assay, the human mast cell line HMC‐1 stimulated thymidine uptake in HRS cell lines, and the stimulation could be blocked using CD30L‐specific monoclonal antibodies. In conclusion, mast cells are present in HD tumours and are the predominant CD30L‐expressing cells. CD30L–CD30 interaction is a pathway by which mast cells may stimulate DNA synthesis in HRS cells.

Expression of CCL5/RANTES by Hodgkin and Reed-Sternberg cells and its possible role in the recruitment of mast cells into lymphomatous tissue

HL is a malignant lymphoma characterized by a small number of malignant HRS cells among a major population of infiltrating reactive cells, e.g., lymphocytes and eosinophils. We previously reported that mast cells are present in HL‐affected lymph nodes and therein are the predominant CD30L‐expressing cells. The CD30L expressed on mast cells is functionally active and can provide stimulatory signals to HRS cells. Thus, mast cells constitute an important portion of the infiltrating reactive cells that contribute to tumor progression in HL. Control of the recruitment of this previously unrecognized cell and its interactions with tumor cells are essentially unknown. To elucidate if mast cells might be specifically attracted to the tumor area by chemokines produced by HRS cells, we investigated chemokine expression in HL cell lines and in vivo. By RNase protection assay, mRNA expression of several chemokines could be detected in the cell lines. Despite the heterogeneous expression profile exhibited by the cell lines, 4 of 5 expressed CCL5 (RANTES) mRNA. RT‐PCR and immunohistochemistry confirmed expression of CCL5 in vivo. Furthermore, secreted CCL5 was detected in conditioned media from 3 of the cell lines. In a migration assay, we found that CCL5 present in conditioned medium could induce mast cell migration. Taken together, our results suggest that CCL5 produced by HRS cells is one mechanism by which mast cells can be attracted into the tumor tissue in HL.

Mast cell infiltration is a favourable prognostic factor in diffuse large B-cell lymphoma

Previous studies indicate that the inflammatory response in diffuse large B‐cell lymphomas (DLBCL) is important for the clinical outcome. Mast cells are key regulators in this response; we investigated whether the number of tryptase‐positive mast cells is correlated with clinical outcome. Patients with many mast cells had a significantly better event‐free survival (EFS) compared to those with few mast cells (P < 0·03 in both germinal centre (GC) and non‐GC DLBCL. This supports the idea that the infiltration of mast cells is a reflection of the host inflammatory response and is related to a favourable outcome.

Angiogenesis and mast cells in Hodgkin lymphoma.

Hodgkin lymphoma (HL) is a malignant disorder characterised by few tumour cells surrounded by a massive infiltrate of inflammatory cells, fibrosis, and microvessels. Therefore, it is a good model in which to study the interplay between tumour cells and the microenvironment. In a population-based series, stage IIB had poor prognosis, equivalent to the most advanced stage (stage IV). The most prominent negative prognostic factor was tumour bulk in the mediastinum (often large fibrotic tumours). The tumour cells expressed interleukin-9 (IL-9) in their cytoplasm in half of the cases. These cases had an over representation of nodular sclerosis histology (characterised by fibrotic bands) and infiltration of eosinophils and mast cells in the tumours. Despite this, IL-9 expression was not a negative prognostic factor. A role of inflammatory cells is to contribute to angiogenesis. Yet, a correlation between high microvessel count and high mast cell number in HL tumours was not identified, in contrast to other lymphomas. However, a correlation to poor prognosis was seen for cases with high microvessel count. Eosinophils contain eosinophil cationic protein (ECP). ECP was cytotoxic to cells from two HL cell lines of B-cell origin and one HL line of T-cell origin. At high concentrations, the cytotoxic effect was not as pronounced for the line of T-cell origin. If the in vitro cell lines are representative of HL in vivo, eosinophils may have different roles in different HL tumours. In addition to the effect from tumour cells, host-related factors contribute to the inflammatory infiltrate in HL. A history of asthma and hives, and carrying the ECP434GG genotype were associated with elevated numbers of eosinophils, whereas, history of tobacco smoking was associated with lower numbers. HL is a complex tumour consisting of recruited and subverted normal cells, fibrosis and angiogenesis: these constitute the microenvironment, which likely supports tumour cell growth, and differs between patients.

IL-9 expression contributes to the cellular composition in Hodgkin lymphoma

Objectives: The presence of numerous mast cells or eosinophils in Hodgkin lymphoma (HL) tumours have both been described as negative prognostic factors. One cytokine related to HL is interleukin‐9 (IL‐9) and it is known to affect both mast cells and eosinophils. The aim of this study was to explore if the expression of IL‐9 correlates to the presence of these inflammatory cells in HL tumours. Methods: In 131 HL biopsies, immunostainings for IL‐9 and IL‐9 receptor (IL‐9R) were performed. The same material was previously stained for mast cells and eosinophils. These data were correlated to clinical and survival data from all patients. Results: Fifty‐three percent of cases were positive for IL‐9 and 19% were positive for IL‐9R in the cytoplasm of the tumour cells. The IL‐9 positive patients had more eosinophils (P = 0.002) and mast cells (P = 0.02) in their tumours, more often a nodular sclerosis histology (P < 0.0001), a higher white‐blood‐cell count (P = 0.006) and a higher erythrocyte sedimentation rate (P = 0.003) at the time of diagnosis. Conclusions: IL‐9 expression is related to the histology, clinical picture and the presence of eosinophils and mast cells in HL. These results indicate that IL‐9 is an important part of the cytokine network and inflammatory infiltrate in HL.

Expression of Mast Cell Tryptases in Hodgkin and Reed-Sternberg (HRS) Cells

Tryptase is the most abundant protease in human mast cells, and is often used as a marker for the enumeration of mast cells in tissue. Here we report that tumour cells from Hodgkin lymphoma, the so called Hodgkin and Reed‐Sternberg cells, can express tryptase. Hodgkin lymphoma cell lines expressed mRNA for both α‐ and β‐tryptase and also produced the protein, although at much lower concentrations than mast cells. However, the frequency of tryptase positive HRS‐cells in situ was very low. This report demonstrates that tumour cells of lymphoid origin can express tryptase in vitro and in situ.