Effects of activated serum factor on the induction of Epstein-Barr virus antigens and cell differentiation

n-Butyrate and 12-0-tetradecanoylphorbol-13-acetate (TPA) have been shown to be potent inducers of Epstein-Barr virus (EBV) antigen synthesis (10, 18) and cell differentiation (1,2). Activated serum factor (SF) has also been reported to induce virus antigen synthesis and moreover it is capable of cooperative action with other inducers (5). We have demonstrated with an EBV-carrying lymphoma cell line (Raji) that activated SF can also induce the appearance of some cellular alterations, specific for early steps of the productive virus cycle in a low proportion of cells. In addition cell differentiation towards plasma cell was noted in about 8 per cent of SF-treated cells. It was confirmed that activated SF enhances the induction of virus antigens by n-butyrate or TPA as detected by the immunofluorescence technique. It was shown that it also potentiates the development of virus-induced changes in cellular morphology and the cell differentiation induced by these drugs. This effect was more pronounced in combination with TPA than with butyrate. Possible relationships between cell differentiation and virus-antigen expression are discussed.