FEMS Microbiology Letters 100 (1992) 449-454 © 1992 Federation of European Microbiological Societies 0378-1097/92/$05.00 Published by Elsevier 449 FEMSLE 80022 Epstein-Barr virus-transformed B lymphocytes produce low molecular mass molecules with autocrine growth factor and competence factor activity Carlo Garzelli, Agostino Bazzichi, Addawe Mohamed Dayah, Maria Manunta, Marina Incaprera and Giuseppe Falcone Department of Biomedicine, Section of Microbiology, University of Pisa, Pisa, Italy Received 26 May 1992 Accepted 11 June 1992 Key words: Epstein-Barr virus; Cell transformation; Growth factors 1. SUMMARY A human Epstein-Barr virus (EBV)-positive lymphoblastoid B cell line, named BA-D10-4, produces a factor of a molecular mass less than 10 kDa that promotes cell proliferation of both BA-D10-4 cells and other human T or B lym- phoid cell lines, either EBV-positive or -negative. The factor synergizes with higher molecular mass autocrine growth factors and makes both BA- D10-4 cells and B cell lines from Burkitt's lym- phoma, but not cells from T cell leukemia, more responsive to interIeukin-1 and interleukin-6. Therefore, this low molecular mass factor seems to be an autocrine growth factor per se and to have the characteristics of a competence factor. Correspondence to." C. Garzelli, Dipartimento di Biomedicina, Sezione di Microbiologia, Via San Zeno 35-39, 56100 Pisa, Italy. 2. INTRODUCTION Epstein-Barr virus (EBV) is associated with endemic Burkitt's lymphoma (BL) and nasopha- ryngeal carcinoma and seems to play a role in the pathogenesis of B cell lymphomas in patients with severe congenital or acquired immunodeficiency [1]. EBV latently infects human B lymphocytes inducing lymphoblastoid cell transformation and immortalization; it has been suggested that EBV-transformed B cells may become indepen- dent of exogenous growth factors that normally control B cell proliferation, by acquiring the abil- ity to synthesize and respond to autocrine, self- stimulating molecules. Although first described at the beginning of the 1980s, EBV-transformed B cell-derived autocrine growth factors are poorly understood; so far, they include two cytokines, i.e. interleukin 1 (IL-1) [2,3] and IL-6 [4,5], the adult T cell leukemia-derived factor (ADF/thioredoxin), which is also produced by