SUMMARY n-Butyrate has been shown to induce Epstein-Barr virus (EBV) antigen synthesis in certain EBV-carrying lymphoma lines . We have studied the effect of n-butyrate on two EBV-positive Burkitt lymphoma lines by immunofluorescence and electron microscopy. In the producer line P3HR-1, the drug induced not only early antigen (EA) and virus capsid antigen (VCA) synthesis, as shown before, but also increased the number of cells containing virus particles. The transition from VCA expression to the formation of virus particles was much more effective in treated cells than in EBV antigen-producing cells of the same line. The productive cycle was associated with the development of characteristic morphological changes. In the non-producer Raji cells, n-butyrate induced EA in only a minor fraction of the cells. There were, however, clear signs of differentiation in the direction of plasma cells. Two days after the addition of n-butyrate 80 % of the Raji cells could be classified as plasmablasts. After 72 h, 20% of the cells appeared as typical plasma cells.

N-Butyrate, an effective inducer of synthesis of Epstein-Barr virus (EBV) antigens in virus-producer P3HR-1 cells, has recently been shown (2) to induce morphological differentiation towards plasma cell in nonproducer Raji cells. The effects of n-butyrate and 12-O-tetradecanoylphorbol-13-acetate (TPA) on both EBV-antigen induction and cell differentiation in two virus-nonproducer lymphoblastoid cell lines, Raji and NC37, were now studied. The following observations were made (1). On its own either drug induced 1-2 per cent of cells to EBV-early-antigen positivity in both lines; their mixture induced 35 and 15 per cent positive cells in Raji and NC37 respectively (2). In Raji, n-butyrate induced about 80 per cent of cells to differentiate to plasmablast or plasma cell morphology, whereas TPA only induced the early stages of differentiation in 8 per cent of cells; a mixture of both inducers produced a similar effect as TPA alone. The addition of TPA alone or butyrate-TPA mixture led to some cellular alterations resembling virus-specific changes in virus-producer cell lines. In NC37, either drug alone or their mixture drove 13 per cent of cells to differentiate into plasmablasts or earlier stages of differentiation. In the presence of TPA protrusions and "loops" were seen on cell surfaces. Evidently, the stage of differentiation at which B-lymphoblastoid cell lines have been arrested can be changed in vitro. However, cell-line dependent and inducer-dependent differences in the differentiation response were apparent.

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A high degree of concordance between the results of immunoelectronmicroscopy and ELISA tests with purified human papillomavirus (HPV-1) particles was observed. The prevalence of HPV-1 antibodies in children living in children's homes was higher than in the general population.