B-LYMPHOCYTES WITH LATENT EBV INFECTION APPEARING IN LONG-TERM BONE-MARROW CULTURES (HLTBMCS) FROM HEMATOLOGICAL PATIENTS INDUCE LYSIS OF STROMAL MICROENVIRONMENT

Human long-term bone marrow cultures (HLTBMCs) are a valuable in vitro model for studying the role of the haemopoietic microenvironment, Her e we report the spontaneous appearance of EBV-positive B cells in 6/40 HLTBMCs from patients with various haematological diseases after 3-5 months of culture. After subcultivation of these cells, a novel type o f cell line could be characterized, which displayed surface markers an d morphological features typical for EBV transformed B-cell lines. As the deproteinized and ultrafiltrated culture supernatants of these cel l lines were found to contain an agent with stroma toxic properties, t hey were termed SSB lines (stroma-toxic-agent-secreting B-cell lines), This agent also exhibited a colony-inhibitory activity on in vitro my elopoiesis and erythropoiesis. These properties are typical for the tw o polyamines spermine and spermidine which were detected at elevated l evels in the culture supernatants of SSB lines. The hypothesis that la tent presence of EBV in bone marrow may induce an increased synthesis of spermine and spermidine, which are known to be associated with mali gnant haematological diseases and bone marrow aplasia, is discussed.