INTRATUMORAL PRODUCTION OF IL-6 IN B-CELL CHRONIC LYMPHOCYTIC-LEUKEMIA AND B-LYMPHOMAS

Interleukin-B is a major B lymphocyte growth factor, and may play a ro le in the proliferation of malignant B lymphocytes. In order to provid e arguments supporting such a role, the intratumoral production of IL- 6 was studied by in situ hybridization and immunohistochemistry in 53 neoplastic tissues from B cell chronic lymphocytic leukemia or B lymph omas. IL-6-producing cells were detected in all samples but 5. However , the number of IL-6 producing cells was variable amongst the differen t cases. Increased density of IL-6-producing cells was highly dependen t on the presence of malignant immunoblasts within the neoplastic clon e. IL-6 was produced in a paracrine way, macrophages and endothelial c ells being the main producers of the cytokine while malignant immunobl asts expressed the IL-6 receptor. Taken together, these results sugges t that IL-6 may indeed act as a growth factor for malignant cells in s ome B lymphoproliferations and that this paracrine loop could be the t arget of new therapeutic approaches.