in situ expression of the IL‐I‐α and tnf‐α genes by reed‐sternberg cells in Hodgkin's disease

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Abstract
The histopathologic pattern of tissues involved by Hodgkin's disease (HD) suggests excessive activation of environmental cells by cytokines released by Hodgkin‐Reed‐Sternberg (HRS) cells, which are considered as the neoplastic component of HD lesions. This hypothesis has been supported by many studies performed in vitro using HD cell lines. In this study, we have tried to demonstrate the cytokine‐producing cells in an environment as close as possible to the in vivo conditions, using in situ hybridization onto frozen sections of HD samples. [35S]‐labelled single‐stranded RNA probes were prepared by transcribing human cDNA fragments of the TNF‐α and IL‐1 α genes sub‐cloned into appropriate vectors. A total of 19 specimens of HD lesions, including 7 cases of nodular sclerosing (NS) type and 12 cases of mixed cellularity (MC), were tested with both types of probes. Clinical stages included stage I (6 cases), stage II (4 cases), stage III (6 cases) and stage IV (3 cases). TNF‐α and/or IL‐I α expression was observed in 12 among 19 HD cases. However, neither the histological type nor the clinical status of the patients was correlated with the profile of cytokine secretion. Most of the cytokine‐producing cells could be identified as HRS cells due to their morphological appearance. In 3 cases, simultaneous analysis by immunohistochemistry and in situ hybridization showed that IL‐1 α/TNF‐α mRNA‐producing cells simultaneously expressed the CD30 antigen, thereby confirming the HRS nature of these cells.