title: Requirements for growth of Epstein-Barr virus-transformed cells at low cell densities.
abstract: We investigated the requirements for growth of Epstein-Barr virus-transformed cells at low cell densities in a homotypic system: only Epstein-Barr virus-transformed cells or their products were used to supply feeder activity. The cloning efficiency was increased markedly under conditions favouring close cell-to-cell contact: culture in round-bottomed rather than in flat-bottomed wells or the addition of irradiated Epstein-Barr virus-transformed cells. Further enhancement was obtained by the addition of the tumour promoter phorbol-myristate acetate. Part of this effect was also induced by supernatants of Epstein-Barr virus-transformed cells, in particular when the latter had been stimulated with phorbol ester. Thus, under limiting dilution conditions, Epstein-Barr virus-transformed cells were found to be dependent upon autologous cell-mediated and soluble proliferation-stimulating signals. In such a homotypic feeder system, the cloning efficiency could be enhanced up to eight-fold; a 100% cloning efficiency could not be achieved. Evidence is presented that the residual deficit in cloning efficiency is inherent to these cell lines.
mesh_terms: D000917:Antibody Formation; D001402:B-Lymphocytes / Q000378:metabolism; D002450:Cell Communication; D002455:Cell Division / Q000187:drug effects; D002460:Cell Line; D002472:Cell Transformation, Viral; D003470:Culture Media; D004854:Herpesvirus 4, Human; D006801:Humans; D007958:Leukocyte Count; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D013936:Thymidine / Q000378:metabolism
chemical_list: D003470:Culture Media; D013755:Tetradecanoylphorbol Acetate; D013936:Thymidine