A growth factor different from IL-6 promotes the growth of Epstein-Barr virus-transformed cells at low cell density.

Interleukin-6 (IL-6) was recently described to support the growth of Epstein-Barr (EBV) transformed lymphocytes. However no effect was reported on cloning of EBV transformed lymphocytes under limiting dilution conditions. In this paper we demonstrate that the Supernatant of Human Endothelial Cells (HECS) contains a factor(s) different from IL-6 which induces high cloning efficiency of EBV transformed cell lines, cultured under limiting dilution conditions. Furthermore HECS is superior to IL-6 in all the passages of EBV lymphocytes transformation.