INDUCTION OF THE LYTIC VIRAL CYCLE IN EPSTEIN-BARR-VIRUS CARRYING BURKITT-LYMPHOMA LINES IS ACCOMPANIED BY INCREASED EXPRESSION OF MAJOR HISTOCOMPATIBILITY COMPLEX-MOLECULES

Six Epstein Barr virus (EBV) genome-carrying Burkitt lymphoma (BL) cultures (P3HR-1, Raji, Akata, Daudi, Rael and Jijoye) were induced to enter the lytic cycle. Phorbol esther (TPA), n-butyrate, 5-azacytidine (5AzaC) or anti-IgG were used according to their known inducing capacity on these cell lines. Concomitantly with the appearance of the viral early antigens (EA) in a proportion of cells, the expression of major histocompatibility complex (MHC) class II antigens increased in the cultures. On P3HR-1 and Raji cells class I expression also increased. The enhancement of MHC expression correlated with the efficiency of induction and required only an early event of the viral lytic cycle. Treatment of 3 EBV-negative lymphoma lines (BJAB, Ramos and BL41) with TPA plus n-butyrate or 5AzaC did not influence MHC expression. Moreover, BL lines which carry the EBV genome after having been infected in vitro and which cannot be induced for the viral lytic cycle did not change MHC expression after treatment with the inducing agents. In mixed cultures the allo-stimulatory capacity of induced cells with elevated MHC expression was stronger compared to the untreated ones